July 27, 2018 - total lunar eclipse and the great opposition of Mars
In modern times, the prevalence of fake information about the most simple and understandable astronomical phenomena is literally threatening. This article was written with the aim of increasing the specific amount of truthful information on the Internet, good, there is a wonderful reason for this.
On the night of July 27-28, 2018 two rather rare astronomical phenomena will occur. The fact of their calendar coincidence does not make these phenomena more valuable to science, but creates additional interest around them. Some people consider the coincidence of two astronomical phenomena as some independent phenomenon, which is not entirely correct, but deserves separate consideration from the point of view of understanding how often this happens, and whether the one affects the other in any way.
On July 27, at about 7 am Moscow time, the great opposition of Mars will occur. Similar phenomena occur once every 15 or 17 years. The previous great confrontation took place on August 27, 2003, and it was from that time that the viral fiction, aggravated annually in August:
For 15 years, the epidemic has not subsided. As you can see, the great oppositions of Mars have a significant impact on ignorant minds.
On July 27, at about 8 pm, the half-shadow phases of a lunar eclipse will begin, during which the moon will completely plunge into the earth's shadow (the maximum immersion will occur at 23:22 Moscow time). Eclipse will end at 2 hours 29 minutes - already July 28. The phenomenon will last more than 6 hours. The moment of the great opposition of Mars, as we see, does not fall into the duration of the eclipse. But the temporary difference between the moment of opposition and the central phase of the eclipse is less than a day. Let it be a match criterion. It is quite enough that both phenomena will occur (or at least begin) on the same calendar date.
For a start, let's deal with the essence of the phenomena themselves. What they are, what visual image corresponds to them, what physical or astronomical sense they have.
Wikipedia gives the following definition of the term “Confrontation”:
This is exactly the case when the definition of a concept can lead to even more confusing, since it uses terms that require further clarification.
Ecliptic longitude:
As we see, each following definition requires new definitions. And for a person who does not have the entire base of the basic concepts of astronomy, even the simplest astronomical phenomenon - the confrontation of Mars - can be very vague to understand.
Then maybe we will try to understand the essence of what is happening in some other, shorter way?
In the first approximation, the orbits of the planets are circles of different diameters. This degree of approximation doesn’t suit us very well, especially when the conversation concerns the planet Mars, but to start it will be enough. The orbits are located one inside the other concentrically. In the middle of this “drawing” is the Sun, and then, in order of increasing radius of the orbit, the planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto, if someone missed, since 2006, the big planet of the solar system is no longer considered.
Two planets from this list - Mercury and Venus - are internal. They are always closer to the Sun than the Earth (their orbits are located inside the Earth's orbit). The remaining five - Mars, Jupiter, Saturn, Uranus and Neptune - are external. They are always farther from the sun than the earth. And for these celestial bodies such situations are possible when the Earth, moving in an orbit, passes between the planet and the Sun. When viewed from Earth, the Sun and the planet turn out to be practically in opposite directions. The first consequence of this is that for a terrestrial observer, this planet and the Sun are not visible in the sky at the same time, and as soon as one star rises above the horizon, another immediately sets.
This arrangement of the outer planet is called opposition - the direction to it from the Earth is opposite to the direction to the Sun. The planet is in the sky all night. For her observations such position is convenient.
The second consequence is that at the moment of the confrontation (again, in the first approximation), the planet is closest to Earth. Because of this, it looks brighter (brightness, as you know, is inversely proportional to the square of the distance), has large visible dimensions (with a telescope, of course, but this is not noticeable to our eyes). And this is also a positive circumstance for astronomical observations. Therefore, the confrontation of the planets is the best time to explore them from Earth. Astronomers have long tried to use days and weeks close to opposition to explore planets. People who have no relation to astronomy most often simply marvel at the appearance in the sky of star-shaped luminaries of extraordinary brightness, which they had not noticed before in the sky.
Now is the time to remember that in fact the orbits of the planets are not circles. About four centuries ago, Johann Kepler defined planetary orbits with ellipses. Orbits of some orbits are noticeably different from circular ones. Mars is particularly relevant. The value characterizing the elongation (difference from the circle) of an elliptical orbit in astronomy (and mathematics) is called eccentricity. Without going into the deep meaning of this concept, I will simply cite for comparison the eccentricities of the orbits of the planets of the solar system visible to the eye:
An absolutely circular orbit has an eccentricity of zero. Those in the table there. The most significant eccentricity among the orbits of the major planets of the solar system, the orbit of Mercury - 0.2. But Mercury is an inner planet, and there is no opposition to Mercury. The second place in elongation is Mars' orbit ~ 0.1. This is 6 times the eccentricity of the Earth's orbit, and we can easily consider the Earth's orbit as circular - to simplify the understanding of the difference in the mutual arrangements of Earth and Mars.
Such a noticeable elongation of the Martian orbit leads to the fact that in one Martian year (the period of Mars’s orbit around the Sun is approximately two Earth years), the distance from Mars to the Sun varies from 207 to 249 million km. As you can see, the difference, even on the cosmic scale of the solar system is noticeable - more than 40 million kilometers. Approximately with the same difference, the distances from the Earth to Mars change during the confrontations. And if the opposition happens near the perihelion of the Martian orbit (perihelion is the nearest point of the planetary orbit to the Sun), then Mars and Earth are separated by less than 60 million kilometers. If the Earth and Mars are on the same straight line on one side of the Sun near the aphelion of the Martian orbit, then, in spite of the fact that this opposition, between the planets will be about a hundred million kilometers.
And indeed, all the most significant discoveries in astronomy related to the planet Mars, made with the help of telescopes, occurred during the "close" confrontations. And astronomers began to call the confrontation, during which Mars and Earth are closer than 60 million kilometers from each other, great.
It was during the great opposition of 1877 by the American astronomer Asaf Hall that two Mars satellites Phobos and Deimos were discovered, which are essentially small asteroids of irregular shape, once gravitationally captured by Mars (according to one hypothesis); and the beginning of the so-called "Martian fever", when Giovanni Schiaparelli saw, among other details of the surface of the planet, thin straight lines connecting the dark, called "seas", space. And although the existence of “Martian canals” was not confirmed later, every great opposition of Mars attracted astronomers to the telescopes' eyepieces, and science fiction writers tirelessly wrote thousands of pages, embodying on them their wildest assumptions about possible life on a planet similar to Earth.
Let us consider the conditions under which the Great confrontations occur. To do this, we need an acquaintance with another important astronomical value - heliocentric longitude. If you look at the Solar system from its north pole (and it also has it, but we will not define this concept now - maybe we will be able to deal with it and other astrometric terms in the next article). We will again see the concentric structure of the planetary orbits. Each planet is somehow located in its orbit. The orbit itself is also somehow oriented in space. But we do not yet have a “point of support” in order to cling to something, and then count the coordinates in some units and determine the positions of the planets in such a simple drawing.
Historically, the reference point was the direction of the vernal equinox. Look, the ray leaving the center of the Earth in the direction of the Sun at that moment, when on Earth the day is equal to night and the (astronomical) spring comes - this ray goes somewhere in the direction of the constellation Pisces. In fact, in the direction of that line, which is the intersection of the plane of the ecliptic and the celestial equator, but omit these details. It is important to us that the direction is somehow determined. Now, but relying on the center of the Sun, we can lay the angles between this and all other directions on the plane of our simplified scheme of the Solar System.
For example, we can measure how different are the directions to the vernal equinox and the point of the Martian orbit where it is closest to the Sun? - it turns out, at 336 degrees (in the counterclockwise direction, in which all the planets move around the Sun). This value is called the longitude of the perihelion. It is interesting to know on what day each year the Earth passes this point (with the same heliocentric longitude) of the orbit, above which the perihelion of Mars is located? After all, if a confrontation ever happens that day, it will be a record close.
Happy "Martian day" falls on the very end of August - August 28 or 29, depending on the year. Here is the time to recall the previous great opposition of Mars in 2003, which happened exactly on the aforementioned days of August (practically), and for its exclusivity it was called the “greatest” opposition of Mars. Yes - nowadays simply you will not surprise anyone with the great opposition of Mars. But, really, then the Earth and Mars were separated by only 55.8 million km.
And what about the current great opposition? It is, alas, not so close and it could even be called “too big”, since the distance between the Earth and Mars on July 27, 2018, and the days nearest to this date will be 58 million kilometers, which is closer to the threshold, beyond which confrontations are no longer considered great than to the “Greatest” confrontations.
Now it is interesting to recall one interesting clarification, which is expressed in the fact that if during the greatest confrontation of Mars, the day of confrontation and the day of maximum convergence of the Earth and Mars actually coincide, then for most of the other confrontations this is not the case. For example, this year the opposition of Mars, when it will confront the Sun on the celestial sphere, will happen on the morning of July 27, but due to the ellipticity of the orbit, Mars will be closest to Earth on the night of July 31 to August 1.
The second interesting clarification is that the position of the perihelion of the Martian orbit changes with time. For a thousand years, the angle between the direction to the vernal equinox and the perihelion of Mars increases by more than 4 degrees. And that period on the calendar grid, in which great confrontations can happen, will shift 4 days ahead in a thousand years.
Now great confrontations can occur between July 24 and October 2. In the future, these dates will change slightly. In the past, they were also slightly different. Although it is not so important now.
Since the criterion by which the Mars oppositions are defined as “great” is very conditional, it’s difficult to talk about some unambiguous calculation of these events at a considerable distance from the present moment into the past or the future. Simply put, the great confrontations of Mars occur once every 15 or 17 years with a rather convoluted alternation of time intervals separating them. As an example, confrontations from a century and a half ago in the present era can be cited:
Such tables can be easily found on dozens or hundreds of sites on the Internet. But then the interesting begins. The confrontation of July 13, 2065 is formally a little short of a great one, since at the very moment of the confrontation Mars and Earth will be separated by a distance of 60.191 million km - it would seem - a trifle, and does not pass under the criterion. But - in the evening of July 18 - having already passed the confrontation - Mars will come closer to Earth to 59.790 million km. And here it is already difficult for him to deny greatness, since all the days surrounding the confrontation itself are considered an era of confrontation. Two years later, another great confrontation will happen - October 3, 2067, when Mars will be just a little closer, but also completely below the bar - 59.94 million km at the time of the confrontation, and - 59.34 million km with maximum convergence five days earlier. And no one knows how the astronomical public will relate to the classification of these phenomena almost half a century from today. Moreover, if we consider the opposition carefully, it can be seen that the sum of the distances separating the Earth and Mars (60.19 + 59.94 = 120.13) exceeds 120 million kilometers for two, which means that theoretically it is possible that after 15 years no great confrontation will happen in the next two years, judging them strictly. And then another 15 years Mars will be objectively far to correct this state of affairs. which means that it is theoretically possible that, after 15 years, not a single great confrontation will happen in the next two years, judging them strictly. And then another 15 years Mars will be objectively far to correct this state of affairs. which means that it is theoretically possible that, after 15 years, not a single great confrontation will happen in the next two years, judging them strictly. And then another 15 years Mars will be objectively far to correct this state of affairs.
It may have arisen, but did not fall into the attention of astronomers of past centuries, since the phenomenon itself - “the great opposition of Mars” - was introduced only when it became possible to accurately determine the distances to the planets, that is, relatively recently.
Why, in some confrontations, Mars shines with a surprisingly bright luminary, and in others - only an ordinary reddish "star" - neither ancient astronomers nor contemporaries of Galileo - did not know this. And even in the era of the invention of the telescope, among serious astronomers there were many supporters of the theories about crystal spheres and ideal circles instead of elliptical orbits.
First of all, the brightness of the planet is very different. Between confrontations, when Mars is lost in the evening or morning dawn, its brilliance is comparable to the brightness of one of the stars in the Ursa dipper and no one pays attention to it. During distant confrontations, when the Earth and Mars are separated by hundreds of millions of kilometers, Mars is noticeably brighter, and already successfully competes with the brightest stars in the sky. His characteristic magnitude is -1m. That is, it is brighter than most stars, but weaker than Sirius (Big Dog's alpha is the brightest star in the sky). But during the great confrontation Mas's brilliance reaches -2.9m and then Mars becomes the brightest star of the earth after the Sun, the Moon and Venus. And if we consider that neither the Sun nor Venus does not shine at night, then during the great opposition of Mars only the Moon can shine brighter in the sky than it.
And here we remember that the upcoming July 27, 2018 great opposition of Mars will occur on the same date with a total lunar eclipse - no less outstanding than the opposition of Mars.
Even 10 years ago, it seemed to me that it was not necessary to explain the nature of such phenomena, and they all more or less clearly imagine what caused the eclipses to happen - that celestial bodies cast shadows. And either an observer (a case characteristic of a solar eclipse) or another celestial body (this is just a lunar eclipse) can fall into the shadow of a celestial body. I understand that among the readers of this article such basics are probably known, but it is necessary to at least briefly designate them, because consequences, questions, and interesting details follow from these elementary points.
It is not difficult to guess that lunar eclipses — phenomena of transit of the moon through the earth's shadow — occur only when the moon in the sky is opposite to the sun, that is, on a full moon. At the same time, not every full moon is accompanied by a lunar eclipse. The lunar orbit lies in a plane different from that of the earth’s orbit, and most often the moon passes under a shadow or above a shadow. And the shadow falls on average a couple of times a year. And this is not necessarily exactly when it is above the horizon. It often happens that the moon eclipse happens when we have all day long. Or - in bad weather. So, to get on this celestial show - a rare luck and great honor for anyone interested in astronomy - to see how slowly the moon disappears in a dark roundish shroud, how it is covered, acquiring a deep red tint completely unusual for her. as the night glow fades away, yielding to the radiance of the stars and the Milky Way ... how everything returns back, leaving only amazing sensations of belonging to something rare and special. It is not surprising that our ancient ancestors gave eclipses such a significant meaning, not always corresponding to their true nature, but always emphasizing the originality of the event.
As you might guess, there are only two points in the lunar orbit, next to which the moon can "meet" with the shadow of the Earth - these are the so-called lunar nodes. And it may seem that in the year there are two calendar dates, near which eclipses can occur. But in fact, the lunar nodes do not stand still and slowly turn, "running" all the ecliptic for 19 years. To this is added light rocking - changing the angle of inclination of the lunar orbit with respect to the Earth. In combination of the described and many other factors lies the non-triviality of predicting the moments and circumstances of lunar eclipses, which, at least in terms of visual characteristics, are quite different.
The moon is four times smaller than Earth, therefore, it should fit in the earth's shadow. But then, the Earth is smaller than the Sun, and therefore it casts a converging cone of shadow into space. At a distance of a few more than a million kilometers from Earth, the earth’s shadow is finally fading away. But since the Moon is at an average distance of 384 thousand km from the Earth, it succeeds in plunging into the shadow, and at this distance the cross section of the shadow is more than twice the width of the moon.
The Earth casts in the direction opposite to the Sun not only a conically decreasing shadow, but also a conically expanding penumbra. If the observer is in the penumbra, then he sees the solar disk, slightly obscured by the body of the Earth - an analogue of a particular solar eclipse, which occur on the Earth due to a similar "fault" of the Moon.
And any shadow lunar eclipse is preceded by a half-shadow phase - to get to the earth's shadow, the moon has to overcome half-shadow and darken a little in it. But the drop in brightness of the lunar disk, crossing the Earth's partial shade, is almost imperceptible to the eye.
If the full moon comes at some distance from the node of the lunar orbit, the moon may pass by the shadow, but fall into partial shade. Such eclipses are called penumbral. As a rule, they do not receive the attention of a public who is far from science. Even astronomy lovers do not attach much importance to them. But if the Moon is at least a little bit in the shadow, then this is already a shadow eclipse, and everyone who has such an opportunity is watching it. And again, the moon may not fully sink into the shadow, and soon leave it. Then it is a private shadow lunar eclipse.
The upcoming eclipse is complete. Moreover, it is almost central. The center of the moon will pass less than a quarter of a degree to the north (above) of the center of the earth's shadow, but at the same time the southern continental part of the lunar disk, having a maximum brightness outside the eclipse, will hit the center of the shadow. Because of this, the overall decline in the brightness of the moon will be the maximum possible (other things being equal). The upcoming lunar eclipse will be one of the darkest eclipses, which undoubtedly makes it unique, and for science its observation can bring a lot of useful data about the Earth's atmosphere.
During total lunar eclipses - even the darkest - the moon does not disappear in the sky at all. But its appearance is changing. Instead of a bright white-yellow disk shining in the night, only dark-red remains in the sky — sometimes, barely noticeable — an obscure ghost of the Moon. How does sunlight reach the moon if it is completely submerged in the earth's shadow?
During an eclipse, the Moon is shielded by the body of the Earth only from direct sunlight, but not from the refracted and scattered by the Earth's atmosphere. Of the entire spectrum of visible rays of the moon, only the longest wavelengths — red and orange rays — reach. The rest are absorbed by the earth's atmosphere. Through photometric and spectral observations of the eclipsed moon, astronomers can get quite a lot of information about the processes occurring in the Earth’s atmosphere. Fans of astronomy also have the unique opportunity to take a picture of both the Moon and the Milky Way at the same time, because both of them usually capture the photo or even see it, the bright full moon illuminates the sky so much that you can’t see the Milky Way on it nor faint stars.
In our case, during an eclipse, it will be possible to see at the same time (and, if you wish, photograph the memory) two red luminaries at once: shining brighter than all the stars and planets of Mars, and just six degrees to the north (above) dim eclipsed Moon. It should be added that simultaneously with the great opposition of Mars and the total lunar eclipse, another astronomical phenomenon will occur on July 27 - the conjunction of the Moon and Mars - so astronomers refer to the relative position of the stars when one of them passes the other at a minimum distance from each other. (Strictly speaking, when planets join, their ecliptic longitudes — analogous to geographic longitudes, only on the celestial sphere — turn out to be equal.) On the night of the eclipse, the Moon and Mars will divide only 6 degrees of arc on the celestial sphere. This is an illusory convergence,
As we have already found out, the lunar eclipses occur on average a couple of times a year, but they are not always visible in a particular place on the globe. The confrontations of Mars occur approximately once every two years, and the great once every 15 - 17 years. But so that both of them at once?
I am afraid that in astronomy there is no special formula for calculating the dates of such coincidences. And the following similar coincidence of circumstances can be predicted only by a sequential brute force method - it is necessary to check the confrontation after the confrontation - is there an eclipse in addition to it? You can recall the sign of the nearest great oppositions and check them all. But - no - this will not happen on any of these dates.
It can be roughly estimated how often more or less favorable circumstances can occur for the occurrence of a great opposition and a lunar eclipse simply by multiplying the periods of their cyclicity, assuming that they are not multiples. True, with regard to the great oppositions of Mars, it is not clear which period to use is 15 or 17 years. You can use their amount - 32 years. And with respect to eclipses, the period of full revolution of the line of lunar nodes is relevant - the so-called “draconic period” of ~ 19 years. And we will get 608 years. This figure does not guarantee the obligatory repetition of such a coincidence, but only illustrates the order of the time interval through which such coincidences could be repeated. Of course, a deeper analysis would reveal additional patterns, which probably delayed the next possible coincidence of the great opposition of Mars and the total lunar eclipse. But we will not do this in this article, but simply conclude that something interesting has fallen to our lot. And you probably should take advantage of this if possible - at least look out the window, or go out into the street - in case of good weather - before midnight Moscow time on July 27, 2018.
In conclusion, I would like to present some useful tips on observing and photographing the Moon and Mars using amateur means that are not so expensive and are most certainly available to most readers.
Having an inexpensive amateur ultrazoom camera and a photo stick, you can make good photographs of the moon in various phases of the eclipse. Of particular interest will be exactly the pictures of the full phase. You need to know which photo options are best to use.
Despite the fact that shooting at night requires longer exposures, it is better to limit yourself to a low ISO value right from the start. especially if an inexpensive camera is used. At high ISO values, you shorten the shutter speed and avoid possible blurring of the subject, but the image will be noisy, grainy, with faded colors. The optimal value is ISO 100. Depending on the quality of the matrix used in a particular camera, you can raise the ISO to 200, 400, but 800 will definitely be an overestimated and questionable value. However, you can experiment, bearing in mind this warning.
Using the zoom from 10x and above, you can already remove many details of the lunar relief - mountain chains, lunar seas, the largest craters and light rays stretching thousands of kilometers from them, generated by the ejected substance as a result of the impact and explosion of the meteoroid that formed the crater. But, if we talk about the era of the full moon and specifically about the night of the eclipse, then at this time on the moon from the Earth are not visible shadows, emphasizing the relief. Therefore, many of its details will not be visible - not for a camera, nor for an observer armed with a telescope. It must be said that the full moon is not the most successful phase for observing the moon and photographing it. However, this is not a reason to abandon shooting altogether. You just have to be prepared for the fact that most of the craters on the photo will not work. But it will be perfectly visible all the "moon map of the seas and bays."
Practice shows that ISO 100 and the zoom from 10x and above are relevant exposure of about 1/100 of a second. If the moon is high in the sky, then it is brighter, because the absorption of its light in the atmosphere is then minimal, and exposure of 1/160 is suitable - 1/200 second. But on the night of July 27-28, the moon will be rather low above the horizon. At the latitude of Moscow, its height will be no more than 15 degrees. This is quite low, and exposure may be required even longer than 1/100 of a second - for example, 1/60. At the same time photographing with hands will lead to blurring the image. A tripod is required for a clear, non-blurred image. But, even using a tripod, you need to take a picture with a 2-second delay of the self-timer to avoid vibration from pressing the shutter button.
It is best to use manual focus if the camera has this functionality. If the focus is only automatic, then either the camera itself will focus on the Moon (which is common for most cameras), or you will have to use an auxiliary object located at a considerable distance - pressing the shutter button halfway and focus on a distant lamp or window, and therefore transfer the camera to The moon, and even then press the button to the end and take a picture.
For the eclipsed moon will require a completely different exposure values. It is difficult to give an accurate recommendation in advance, since the brightness of the eclipsed moon from eclipse to eclipse varies greatly. But this is definitely not hundredths or tenths of a second, but closer to one or several seconds. And if you want to simultaneously remove the Moon in an eclipse, Mars, and the Milky Way extending from the constellation Sagittarius through the entire summer sky, then you will definitely need excerpts of 15 seconds or more.
In this case, whatever you shoot, the diaphragm should be opened as far as possible, as far as the optical scheme of the camera allows.
Binoculars or a telescope will be very useful for observing the moon during an eclipse (and beyond the eclipse too). But for Mars, even on the night of the great opposition, the pipe will be small. I must say that Mars is a small planet and even in a telescope sometimes looks like a tiny disk. To understand what we are dealing with, I will give this analogy. The 10-kopek coin, which has a diameter of about 1 cm, looks like Mars, from a distance of 100 meters. Can you see this coin on the opposite side of the football field? And consider on it any details? And take a picture? And if you imagine that you are looking at it also through the aquarium, the water in which constantly moves?
If you think about the above allegory, you may understand what the astronomers are dealing with. And even using a telescope with a magnification of 100 times, which creates the illusion of reducing the distance to a coin to 1 meter, you are not able to exclude from the scheme a “bubbling aquarium” of the earth’s atmosphere, which will not allow us to consider new details even at high magnifications. It is because of the detrimental effect of the atmosphere on the image quality of celestial objects, astronomers, already a few centuries ago, began to look for places for their observatories in the mountains, climbing higher and higher. And now the most breakthrough research and discoveries are made, as a rule, either with the help of orbiting telescopes, or with automatic robot stations landing on the surface of the planet under study. From the Earth, of course, do not see what the Curiosity rover sees with their cameras.
In the amateur telescope during the great opposition of Mars you can only look at the polar cap facing the Earth, a couple of dark spots of the Martian seas and, possibly, the Grand Canyon - a giant break on the surface and the most visible of the Martian channels - the only one that has been objectively confirmed turned out to be an illusion).
Finishing this lengthy article, I want to wish all its readers good weather, favorable conditions for observations — a comfortable temperature, a calm atmosphere and an open horizon in the directions southeast – south – southwest. After all, it is in this part of the firmament that Mars will be visible in the great opposition and the Moon in an eclipse at a low altitude on the night of July 27-28, 2018.
For more detailed information about this and another celestial body, to determine the conditions of their visibility in your locality you will be greatly helped by the astronomical program Stellaruim - freely distributed and working on most computers.
I cite the main points of the upcoming eclipse as an attachment to the article, so that they are not lost in the immense text.
UT - the moment according to the Universal Time
MT - the moment according to Moscow time
Map of the visibility of the eclipse from NASA (the eclipse is seen completely in the white zone):
On the night of July 27-28, 2018 two rather rare astronomical phenomena will occur. The fact of their calendar coincidence does not make these phenomena more valuable to science, but creates additional interest around them. Some people consider the coincidence of two astronomical phenomena as some independent phenomenon, which is not entirely correct, but deserves separate consideration from the point of view of understanding how often this happens, and whether the one affects the other in any way.
What will happen?
The first phenomenon
On July 27, at about 7 am Moscow time, the great opposition of Mars will occur. Similar phenomena occur once every 15 or 17 years. The previous great confrontation took place on August 27, 2003, and it was from that time that the viral fiction, aggravated annually in August:
“On August 27, raise your eyes to the night sky. On this night, the planet Mars will pass only 34 thousand miles from Earth. It will look like two moons ... "
For 15 years, the epidemic has not subsided. As you can see, the great oppositions of Mars have a significant impact on ignorant minds.
The second phenomenon
On July 27, at about 8 pm, the half-shadow phases of a lunar eclipse will begin, during which the moon will completely plunge into the earth's shadow (the maximum immersion will occur at 23:22 Moscow time). Eclipse will end at 2 hours 29 minutes - already July 28. The phenomenon will last more than 6 hours. The moment of the great opposition of Mars, as we see, does not fall into the duration of the eclipse. But the temporary difference between the moment of opposition and the central phase of the eclipse is less than a day. Let it be a match criterion. It is quite enough that both phenomena will occur (or at least begin) on the same calendar date.
For a start, let's deal with the essence of the phenomena themselves. What they are, what visual image corresponds to them, what physical or astronomical sense they have.
The great opposition of Mars
Wikipedia gives the following definition of the term “Confrontation”:
“Confrontation (opposition) is such a position of the celestial body of the Solar system, in which the difference of its ecliptic longitudes and the Sun is 180 °. Thus, this body is located approximately on the continuation of the “Sun-Earth” line and can be seen from the Earth approximately in the direction opposite to the Sun. Confrontation is possible only for the upper planets and other bodies that are farther from the Sun than the Earth. ”
This is exactly the case when the definition of a concept can lead to even more confusing, since it uses terms that require further clarification.
Ecliptic longitude:
“One of the coordinates in the ecliptic coordinate system; the angle measured along the ecliptic to the east, between the vernal equinox and the meridian passing through the heavenly body and the ecliptic poles. ”
Surdin VG, GAISH http://www.astronet.ru/db/msg/1162196
As we see, each following definition requires new definitions. And for a person who does not have the entire base of the basic concepts of astronomy, even the simplest astronomical phenomenon - the confrontation of Mars - can be very vague to understand.
Then maybe we will try to understand the essence of what is happening in some other, shorter way?
In the first approximation, the orbits of the planets are circles of different diameters. This degree of approximation doesn’t suit us very well, especially when the conversation concerns the planet Mars, but to start it will be enough. The orbits are located one inside the other concentrically. In the middle of this “drawing” is the Sun, and then, in order of increasing radius of the orbit, the planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto, if someone missed, since 2006, the big planet of the solar system is no longer considered.
Two planets from this list - Mercury and Venus - are internal. They are always closer to the Sun than the Earth (their orbits are located inside the Earth's orbit). The remaining five - Mars, Jupiter, Saturn, Uranus and Neptune - are external. They are always farther from the sun than the earth. And for these celestial bodies such situations are possible when the Earth, moving in an orbit, passes between the planet and the Sun. When viewed from Earth, the Sun and the planet turn out to be practically in opposite directions. The first consequence of this is that for a terrestrial observer, this planet and the Sun are not visible in the sky at the same time, and as soon as one star rises above the horizon, another immediately sets.
This arrangement of the outer planet is called opposition - the direction to it from the Earth is opposite to the direction to the Sun. The planet is in the sky all night. For her observations such position is convenient.
The second consequence is that at the moment of the confrontation (again, in the first approximation), the planet is closest to Earth. Because of this, it looks brighter (brightness, as you know, is inversely proportional to the square of the distance), has large visible dimensions (with a telescope, of course, but this is not noticeable to our eyes). And this is also a positive circumstance for astronomical observations. Therefore, the confrontation of the planets is the best time to explore them from Earth. Astronomers have long tried to use days and weeks close to opposition to explore planets. People who have no relation to astronomy most often simply marvel at the appearance in the sky of star-shaped luminaries of extraordinary brightness, which they had not noticed before in the sky.
Note
Строгости ради надо сказать, что появление на небе непривычно-ярких объектов не всегда связанно с планетами вступающими в противостояние с Солнцем. Например планета Венера достигает наибольшей яркости между наибольшей элонгаций и нижним соединением, и становится причиной частых сообщений об НЛО. Но наша статья все-таки о другом.
Now is the time to remember that in fact the orbits of the planets are not circles. About four centuries ago, Johann Kepler defined planetary orbits with ellipses. Orbits of some orbits are noticeably different from circular ones. Mars is particularly relevant. The value characterizing the elongation (difference from the circle) of an elliptical orbit in astronomy (and mathematics) is called eccentricity. Without going into the deep meaning of this concept, I will simply cite for comparison the eccentricities of the orbits of the planets of the solar system visible to the eye:
| Mercury | 0.20563593 |
| Venus | 0,0068 |
| Land | 0,01671123 |
| Mars | 0.0933941 |
| Jupiter | 0.048775 |
| Saturn | 0.055723219 |
An absolutely circular orbit has an eccentricity of zero. Those in the table there. The most significant eccentricity among the orbits of the major planets of the solar system, the orbit of Mercury - 0.2. But Mercury is an inner planet, and there is no opposition to Mercury. The second place in elongation is Mars' orbit ~ 0.1. This is 6 times the eccentricity of the Earth's orbit, and we can easily consider the Earth's orbit as circular - to simplify the understanding of the difference in the mutual arrangements of Earth and Mars.
Such a noticeable elongation of the Martian orbit leads to the fact that in one Martian year (the period of Mars’s orbit around the Sun is approximately two Earth years), the distance from Mars to the Sun varies from 207 to 249 million km. As you can see, the difference, even on the cosmic scale of the solar system is noticeable - more than 40 million kilometers. Approximately with the same difference, the distances from the Earth to Mars change during the confrontations. And if the opposition happens near the perihelion of the Martian orbit (perihelion is the nearest point of the planetary orbit to the Sun), then Mars and Earth are separated by less than 60 million kilometers. If the Earth and Mars are on the same straight line on one side of the Sun near the aphelion of the Martian orbit, then, in spite of the fact that this opposition, between the planets will be about a hundred million kilometers.
And indeed, all the most significant discoveries in astronomy related to the planet Mars, made with the help of telescopes, occurred during the "close" confrontations. And astronomers began to call the confrontation, during which Mars and Earth are closer than 60 million kilometers from each other, great.
It was during the great opposition of 1877 by the American astronomer Asaf Hall that two Mars satellites Phobos and Deimos were discovered, which are essentially small asteroids of irregular shape, once gravitationally captured by Mars (according to one hypothesis); and the beginning of the so-called "Martian fever", when Giovanni Schiaparelli saw, among other details of the surface of the planet, thin straight lines connecting the dark, called "seas", space. And although the existence of “Martian canals” was not confirmed later, every great opposition of Mars attracted astronomers to the telescopes' eyepieces, and science fiction writers tirelessly wrote thousands of pages, embodying on them their wildest assumptions about possible life on a planet similar to Earth.
Let us consider the conditions under which the Great confrontations occur. To do this, we need an acquaintance with another important astronomical value - heliocentric longitude. If you look at the Solar system from its north pole (and it also has it, but we will not define this concept now - maybe we will be able to deal with it and other astrometric terms in the next article). We will again see the concentric structure of the planetary orbits. Each planet is somehow located in its orbit. The orbit itself is also somehow oriented in space. But we do not yet have a “point of support” in order to cling to something, and then count the coordinates in some units and determine the positions of the planets in such a simple drawing.
Historically, the reference point was the direction of the vernal equinox. Look, the ray leaving the center of the Earth in the direction of the Sun at that moment, when on Earth the day is equal to night and the (astronomical) spring comes - this ray goes somewhere in the direction of the constellation Pisces. In fact, in the direction of that line, which is the intersection of the plane of the ecliptic and the celestial equator, but omit these details. It is important to us that the direction is somehow determined. Now, but relying on the center of the Sun, we can lay the angles between this and all other directions on the plane of our simplified scheme of the Solar System.
For example, we can measure how different are the directions to the vernal equinox and the point of the Martian orbit where it is closest to the Sun? - it turns out, at 336 degrees (in the counterclockwise direction, in which all the planets move around the Sun). This value is called the longitude of the perihelion. It is interesting to know on what day each year the Earth passes this point (with the same heliocentric longitude) of the orbit, above which the perihelion of Mars is located? After all, if a confrontation ever happens that day, it will be a record close.
Happy "Martian day" falls on the very end of August - August 28 or 29, depending on the year. Here is the time to recall the previous great opposition of Mars in 2003, which happened exactly on the aforementioned days of August (practically), and for its exclusivity it was called the “greatest” opposition of Mars. Yes - nowadays simply you will not surprise anyone with the great opposition of Mars. But, really, then the Earth and Mars were separated by only 55.8 million km.
And what about the current great opposition? It is, alas, not so close and it could even be called “too big”, since the distance between the Earth and Mars on July 27, 2018, and the days nearest to this date will be 58 million kilometers, which is closer to the threshold, beyond which confrontations are no longer considered great than to the “Greatest” confrontations.
Now it is interesting to recall one interesting clarification, which is expressed in the fact that if during the greatest confrontation of Mars, the day of confrontation and the day of maximum convergence of the Earth and Mars actually coincide, then for most of the other confrontations this is not the case. For example, this year the opposition of Mars, when it will confront the Sun on the celestial sphere, will happen on the morning of July 27, but due to the ellipticity of the orbit, Mars will be closest to Earth on the night of July 31 to August 1.
The second interesting clarification is that the position of the perihelion of the Martian orbit changes with time. For a thousand years, the angle between the direction to the vernal equinox and the perihelion of Mars increases by more than 4 degrees. And that period on the calendar grid, in which great confrontations can happen, will shift 4 days ahead in a thousand years.
Now great confrontations can occur between July 24 and October 2. In the future, these dates will change slightly. In the past, they were also slightly different. Although it is not so important now.
How often happen the great opposition of Mars?
Since the criterion by which the Mars oppositions are defined as “great” is very conditional, it’s difficult to talk about some unambiguous calculation of these events at a considerable distance from the present moment into the past or the future. Simply put, the great confrontations of Mars occur once every 15 or 17 years with a rather convoluted alternation of time intervals separating them. As an example, confrontations from a century and a half ago in the present era can be cited:
| September 19, 1830 | 15 years |
| August 18, 1845 | 15 years |
| July 17, 1860 | 17 years |
| September 5, 1877 | 15 years |
| August 4, 1892 | 17 years |
| September 24, 1909 | 15 years |
| August 23, 1924 | 17 years |
| July 23, 1939 | 17 years |
| September 10, 1956 | 15 years |
| August 10, 1971 | 17 years |
| September 22, 1988 | 15 years |
| August 28, 2003 | 15 years |
| July 27, 2018 | 17 years |
| September 15, 2035 | 15 years |
| August 13, 2050 | ? |
Such tables can be easily found on dozens or hundreds of sites on the Internet. But then the interesting begins. The confrontation of July 13, 2065 is formally a little short of a great one, since at the very moment of the confrontation Mars and Earth will be separated by a distance of 60.191 million km - it would seem - a trifle, and does not pass under the criterion. But - in the evening of July 18 - having already passed the confrontation - Mars will come closer to Earth to 59.790 million km. And here it is already difficult for him to deny greatness, since all the days surrounding the confrontation itself are considered an era of confrontation. Two years later, another great confrontation will happen - October 3, 2067, when Mars will be just a little closer, but also completely below the bar - 59.94 million km at the time of the confrontation, and - 59.34 million km with maximum convergence five days earlier. And no one knows how the astronomical public will relate to the classification of these phenomena almost half a century from today. Moreover, if we consider the opposition carefully, it can be seen that the sum of the distances separating the Earth and Mars (60.19 + 59.94 = 120.13) exceeds 120 million kilometers for two, which means that theoretically it is possible that after 15 years no great confrontation will happen in the next two years, judging them strictly. And then another 15 years Mars will be objectively far to correct this state of affairs. which means that it is theoretically possible that, after 15 years, not a single great confrontation will happen in the next two years, judging them strictly. And then another 15 years Mars will be objectively far to correct this state of affairs. which means that it is theoretically possible that, after 15 years, not a single great confrontation will happen in the next two years, judging them strictly. And then another 15 years Mars will be objectively far to correct this state of affairs.
Why has this situation never happened in the past?
It may have arisen, but did not fall into the attention of astronomers of past centuries, since the phenomenon itself - “the great opposition of Mars” - was introduced only when it became possible to accurately determine the distances to the planets, that is, relatively recently.
Why, in some confrontations, Mars shines with a surprisingly bright luminary, and in others - only an ordinary reddish "star" - neither ancient astronomers nor contemporaries of Galileo - did not know this. And even in the era of the invention of the telescope, among serious astronomers there were many supporters of the theories about crystal spheres and ideal circles instead of elliptical orbits.
And how much different are the visual characteristics of Mars from opposition to opposition?
First of all, the brightness of the planet is very different. Between confrontations, when Mars is lost in the evening or morning dawn, its brilliance is comparable to the brightness of one of the stars in the Ursa dipper and no one pays attention to it. During distant confrontations, when the Earth and Mars are separated by hundreds of millions of kilometers, Mars is noticeably brighter, and already successfully competes with the brightest stars in the sky. His characteristic magnitude is -1m. That is, it is brighter than most stars, but weaker than Sirius (Big Dog's alpha is the brightest star in the sky). But during the great confrontation Mas's brilliance reaches -2.9m and then Mars becomes the brightest star of the earth after the Sun, the Moon and Venus. And if we consider that neither the Sun nor Venus does not shine at night, then during the great opposition of Mars only the Moon can shine brighter in the sky than it.
Comparison of the apparent size of Mars at different distances from the Earth
Сравнение видимых размеров Марса на различных расстояниях от Земли (при наблюдении в телескоп):
- левое изображение — во время великого противостояния
- среднее — во время обычного противостояния
- правое — вблизи верхнего соединения с Солнцем, в наибольшем удалении от Земли.
And here we remember that the upcoming July 27, 2018 great opposition of Mars will occur on the same date with a total lunar eclipse - no less outstanding than the opposition of Mars.
Let's talk a little about eclipse now.
Even 10 years ago, it seemed to me that it was not necessary to explain the nature of such phenomena, and they all more or less clearly imagine what caused the eclipses to happen - that celestial bodies cast shadows. And either an observer (a case characteristic of a solar eclipse) or another celestial body (this is just a lunar eclipse) can fall into the shadow of a celestial body. I understand that among the readers of this article such basics are probably known, but it is necessary to at least briefly designate them, because consequences, questions, and interesting details follow from these elementary points.
It is not difficult to guess that lunar eclipses — phenomena of transit of the moon through the earth's shadow — occur only when the moon in the sky is opposite to the sun, that is, on a full moon. At the same time, not every full moon is accompanied by a lunar eclipse. The lunar orbit lies in a plane different from that of the earth’s orbit, and most often the moon passes under a shadow or above a shadow. And the shadow falls on average a couple of times a year. And this is not necessarily exactly when it is above the horizon. It often happens that the moon eclipse happens when we have all day long. Or - in bad weather. So, to get on this celestial show - a rare luck and great honor for anyone interested in astronomy - to see how slowly the moon disappears in a dark roundish shroud, how it is covered, acquiring a deep red tint completely unusual for her. as the night glow fades away, yielding to the radiance of the stars and the Milky Way ... how everything returns back, leaving only amazing sensations of belonging to something rare and special. It is not surprising that our ancient ancestors gave eclipses such a significant meaning, not always corresponding to their true nature, but always emphasizing the originality of the event.
As you might guess, there are only two points in the lunar orbit, next to which the moon can "meet" with the shadow of the Earth - these are the so-called lunar nodes. And it may seem that in the year there are two calendar dates, near which eclipses can occur. But in fact, the lunar nodes do not stand still and slowly turn, "running" all the ecliptic for 19 years. To this is added light rocking - changing the angle of inclination of the lunar orbit with respect to the Earth. In combination of the described and many other factors lies the non-triviality of predicting the moments and circumstances of lunar eclipses, which, at least in terms of visual characteristics, are quite different.
We list the main differences between the phenomena falling under the classification "lunar eclipse"
The moon is four times smaller than Earth, therefore, it should fit in the earth's shadow. But then, the Earth is smaller than the Sun, and therefore it casts a converging cone of shadow into space. At a distance of a few more than a million kilometers from Earth, the earth’s shadow is finally fading away. But since the Moon is at an average distance of 384 thousand km from the Earth, it succeeds in plunging into the shadow, and at this distance the cross section of the shadow is more than twice the width of the moon.
The Earth casts in the direction opposite to the Sun not only a conically decreasing shadow, but also a conically expanding penumbra. If the observer is in the penumbra, then he sees the solar disk, slightly obscured by the body of the Earth - an analogue of a particular solar eclipse, which occur on the Earth due to a similar "fault" of the Moon.
And any shadow lunar eclipse is preceded by a half-shadow phase - to get to the earth's shadow, the moon has to overcome half-shadow and darken a little in it. But the drop in brightness of the lunar disk, crossing the Earth's partial shade, is almost imperceptible to the eye.
If the full moon comes at some distance from the node of the lunar orbit, the moon may pass by the shadow, but fall into partial shade. Such eclipses are called penumbral. As a rule, they do not receive the attention of a public who is far from science. Even astronomy lovers do not attach much importance to them. But if the Moon is at least a little bit in the shadow, then this is already a shadow eclipse, and everyone who has such an opportunity is watching it. And again, the moon may not fully sink into the shadow, and soon leave it. Then it is a private shadow lunar eclipse.
The upcoming eclipse is complete. Moreover, it is almost central. The center of the moon will pass less than a quarter of a degree to the north (above) of the center of the earth's shadow, but at the same time the southern continental part of the lunar disk, having a maximum brightness outside the eclipse, will hit the center of the shadow. Because of this, the overall decline in the brightness of the moon will be the maximum possible (other things being equal). The upcoming lunar eclipse will be one of the darkest eclipses, which undoubtedly makes it unique, and for science its observation can bring a lot of useful data about the Earth's atmosphere.
During total lunar eclipses - even the darkest - the moon does not disappear in the sky at all. But its appearance is changing. Instead of a bright white-yellow disk shining in the night, only dark-red remains in the sky — sometimes, barely noticeable — an obscure ghost of the Moon. How does sunlight reach the moon if it is completely submerged in the earth's shadow?
During an eclipse, the Moon is shielded by the body of the Earth only from direct sunlight, but not from the refracted and scattered by the Earth's atmosphere. Of the entire spectrum of visible rays of the moon, only the longest wavelengths — red and orange rays — reach. The rest are absorbed by the earth's atmosphere. Through photometric and spectral observations of the eclipsed moon, astronomers can get quite a lot of information about the processes occurring in the Earth’s atmosphere. Fans of astronomy also have the unique opportunity to take a picture of both the Moon and the Milky Way at the same time, because both of them usually capture the photo or even see it, the bright full moon illuminates the sky so much that you can’t see the Milky Way on it nor faint stars.
In our case, during an eclipse, it will be possible to see at the same time (and, if you wish, photograph the memory) two red luminaries at once: shining brighter than all the stars and planets of Mars, and just six degrees to the north (above) dim eclipsed Moon. It should be added that simultaneously with the great opposition of Mars and the total lunar eclipse, another astronomical phenomenon will occur on July 27 - the conjunction of the Moon and Mars - so astronomers refer to the relative position of the stars when one of them passes the other at a minimum distance from each other. (Strictly speaking, when planets join, their ecliptic longitudes — analogous to geographic longitudes, only on the celestial sphere — turn out to be equal.) On the night of the eclipse, the Moon and Mars will divide only 6 degrees of arc on the celestial sphere. This is an illusory convergence,
How rare are these events?
As we have already found out, the lunar eclipses occur on average a couple of times a year, but they are not always visible in a particular place on the globe. The confrontations of Mars occur approximately once every two years, and the great once every 15 - 17 years. But so that both of them at once?
I am afraid that in astronomy there is no special formula for calculating the dates of such coincidences. And the following similar coincidence of circumstances can be predicted only by a sequential brute force method - it is necessary to check the confrontation after the confrontation - is there an eclipse in addition to it? You can recall the sign of the nearest great oppositions and check them all. But - no - this will not happen on any of these dates.
It can be roughly estimated how often more or less favorable circumstances can occur for the occurrence of a great opposition and a lunar eclipse simply by multiplying the periods of their cyclicity, assuming that they are not multiples. True, with regard to the great oppositions of Mars, it is not clear which period to use is 15 or 17 years. You can use their amount - 32 years. And with respect to eclipses, the period of full revolution of the line of lunar nodes is relevant - the so-called “draconic period” of ~ 19 years. And we will get 608 years. This figure does not guarantee the obligatory repetition of such a coincidence, but only illustrates the order of the time interval through which such coincidences could be repeated. Of course, a deeper analysis would reveal additional patterns, which probably delayed the next possible coincidence of the great opposition of Mars and the total lunar eclipse. But we will not do this in this article, but simply conclude that something interesting has fallen to our lot. And you probably should take advantage of this if possible - at least look out the window, or go out into the street - in case of good weather - before midnight Moscow time on July 27, 2018.
Good advice to observers
In conclusion, I would like to present some useful tips on observing and photographing the Moon and Mars using amateur means that are not so expensive and are most certainly available to most readers.
About choosing a place for observation
Выбирая место для проведения наблюдений помните, что Луна и (особенно) Марс будут видны невысоко надо горизонтом. Поэтому ищите открытую лесную поляну, поле, возвышенность с открытым южным горизонтом. Лучшие условия наблюдения соответствуют более южным широтам. В географических пунктах расположенных севернее 65 градуса СШ Марс летом этого года вообще не восходит над горизонтом, а Луна едва лишь поднявшись зайдет за горизонт вновь. Существует карта видимости затмения, с которой имеет смысл свериться и узнать, будет ли наблюдаться явление в месте вашего пребывания.
Having an inexpensive amateur ultrazoom camera and a photo stick, you can make good photographs of the moon in various phases of the eclipse. Of particular interest will be exactly the pictures of the full phase. You need to know which photo options are best to use.
Despite the fact that shooting at night requires longer exposures, it is better to limit yourself to a low ISO value right from the start. especially if an inexpensive camera is used. At high ISO values, you shorten the shutter speed and avoid possible blurring of the subject, but the image will be noisy, grainy, with faded colors. The optimal value is ISO 100. Depending on the quality of the matrix used in a particular camera, you can raise the ISO to 200, 400, but 800 will definitely be an overestimated and questionable value. However, you can experiment, bearing in mind this warning.
Using the zoom from 10x and above, you can already remove many details of the lunar relief - mountain chains, lunar seas, the largest craters and light rays stretching thousands of kilometers from them, generated by the ejected substance as a result of the impact and explosion of the meteoroid that formed the crater. But, if we talk about the era of the full moon and specifically about the night of the eclipse, then at this time on the moon from the Earth are not visible shadows, emphasizing the relief. Therefore, many of its details will not be visible - not for a camera, nor for an observer armed with a telescope. It must be said that the full moon is not the most successful phase for observing the moon and photographing it. However, this is not a reason to abandon shooting altogether. You just have to be prepared for the fact that most of the craters on the photo will not work. But it will be perfectly visible all the "moon map of the seas and bays."
What shutter speed to use for taking pictures of the moon?
Practice shows that ISO 100 and the zoom from 10x and above are relevant exposure of about 1/100 of a second. If the moon is high in the sky, then it is brighter, because the absorption of its light in the atmosphere is then minimal, and exposure of 1/160 is suitable - 1/200 second. But on the night of July 27-28, the moon will be rather low above the horizon. At the latitude of Moscow, its height will be no more than 15 degrees. This is quite low, and exposure may be required even longer than 1/100 of a second - for example, 1/60. At the same time photographing with hands will lead to blurring the image. A tripod is required for a clear, non-blurred image. But, even using a tripod, you need to take a picture with a 2-second delay of the self-timer to avoid vibration from pressing the shutter button.
It is best to use manual focus if the camera has this functionality. If the focus is only automatic, then either the camera itself will focus on the Moon (which is common for most cameras), or you will have to use an auxiliary object located at a considerable distance - pressing the shutter button halfway and focus on a distant lamp or window, and therefore transfer the camera to The moon, and even then press the button to the end and take a picture.
For the eclipsed moon will require a completely different exposure values. It is difficult to give an accurate recommendation in advance, since the brightness of the eclipsed moon from eclipse to eclipse varies greatly. But this is definitely not hundredths or tenths of a second, but closer to one or several seconds. And if you want to simultaneously remove the Moon in an eclipse, Mars, and the Milky Way extending from the constellation Sagittarius through the entire summer sky, then you will definitely need excerpts of 15 seconds or more.
In this case, whatever you shoot, the diaphragm should be opened as far as possible, as far as the optical scheme of the camera allows.
Binoculars or a telescope will be very useful for observing the moon during an eclipse (and beyond the eclipse too). But for Mars, even on the night of the great opposition, the pipe will be small. I must say that Mars is a small planet and even in a telescope sometimes looks like a tiny disk. To understand what we are dealing with, I will give this analogy. The 10-kopek coin, which has a diameter of about 1 cm, looks like Mars, from a distance of 100 meters. Can you see this coin on the opposite side of the football field? And consider on it any details? And take a picture? And if you imagine that you are looking at it also through the aquarium, the water in which constantly moves?
If you think about the above allegory, you may understand what the astronomers are dealing with. And even using a telescope with a magnification of 100 times, which creates the illusion of reducing the distance to a coin to 1 meter, you are not able to exclude from the scheme a “bubbling aquarium” of the earth’s atmosphere, which will not allow us to consider new details even at high magnifications. It is because of the detrimental effect of the atmosphere on the image quality of celestial objects, astronomers, already a few centuries ago, began to look for places for their observatories in the mountains, climbing higher and higher. And now the most breakthrough research and discoveries are made, as a rule, either with the help of orbiting telescopes, or with automatic robot stations landing on the surface of the planet under study. From the Earth, of course, do not see what the Curiosity rover sees with their cameras.
In the amateur telescope during the great opposition of Mars you can only look at the polar cap facing the Earth, a couple of dark spots of the Martian seas and, possibly, the Grand Canyon - a giant break on the surface and the most visible of the Martian channels - the only one that has been objectively confirmed turned out to be an illusion).
Finishing this lengthy article, I want to wish all its readers good weather, favorable conditions for observations — a comfortable temperature, a calm atmosphere and an open horizon in the directions southeast – south – southwest. After all, it is in this part of the firmament that Mars will be visible in the great opposition and the Moon in an eclipse at a low altitude on the night of July 27-28, 2018.
For more detailed information about this and another celestial body, to determine the conditions of their visibility in your locality you will be greatly helped by the astronomical program Stellaruim - freely distributed and working on most computers.
I cite the main points of the upcoming eclipse as an attachment to the article, so that they are not lost in the immense text.
Good luck!
Application:
| Eclipse phase | UT | MT | Note |
|---|---|---|---|
| The introduction of the moon in partial shade | the phenomenon itself is almost invisible | ||
| The entry of the moon into the shadow | 18:24 | 21:24 | it is already visible and interesting |
| Full immersion of the moon in the shadow - the beginning of the full phase | 19:30 | 22:30 | at this moment only a barely visible dark red circle will remain in the sky from the moon |
| The maximum eclipse phase - the deepest immersion of the moon in the shadow of the earth | 20:22 | 23:22 | the lunar disk is the darkest and at the same time the best conditions for photographing the moon against the background of the starry sky, since the rest of the time the moon strongly prevents photographing stars and it is impossible to simultaneously shoot the moon and the milky way |
| The end of the full phase - the moon begins to emerge from the shadows | 21:13 | 00:13 | the bright edge of the moon begins to look out of the shadows and shine the sky around itself |
| The end of the shadow eclipse | 22:19 | 01:19 | for the human eye, this is perceived as the full return of the moon to the sky in its usual form - the full moon as the full moon, although the moon will still be in terrestrial penumbra, the effect of which on the brightness of the moon can only be determined by special devices - photometers. |
| The end of the penumbral eclipse and the eclipse in general | 23:29 | 02:29 |
UT - the moment according to the Universal Time
MT - the moment according to Moscow time
Map of the visibility of the eclipse from NASA (the eclipse is seen completely in the white zone):