Brief information
Mercury is the planet closest to the sun. The average distance between Mercury and the Sun is 58 million kilometers. The planet has a highly elongated orbit. A year on Mercury lasts 88 days. The planet has a very rarefied helium atmosphere. The pressure created by such an atmosphere is 500 billion times less than the air pressure at the Earth's surface.
Venus- the brightest object in the sky after the Sun and the Moon. Venus makes a complete revolution around the Sun in 225 days. The period of rotation around the axis is 243 days, i.e. The length of the day is the longest among the planets. The atmosphere of Venus is 96.5% carbon dioxide and 3.5% nitrogen.
Necessary equipment
From the point of view of equipment, the observation of Mercury and Venus is not fundamentally different from the observation of other planets. However, there are some nuances. For example, for observations of Venus, achromatic refractors are of little use, which burden the image with great chromatism, which is especially evident due to the dazzling brilliance of the planet. It will not be superfluous to have an equatorial mount or a mount equipped with a Go-To, since observation of the lower planets can and should be carried out in the daytime. But the difficulty of finding a planet during daylight hours makes it almost impossible to use conventional, alt-azimuth mounts.
Details on the surface of Mercury and Venus are barely perceptible with visual observations, and the quality of all the optical components of the telescope should not be in doubt. It is recommended to have high-quality planetary eyepieces - orthoscopics and monocentrics.
A set of color filters will also come in handy. Orange, red and dark red (useful on large telescopes) filters will help improve the contrast of the planets when observing in the daytime and twilight sky. Green, purple and blue bring out the dark details in the planetary disks.
Attention! When making daytime observations of Mercury or Venus, in no case look at the Sun through the eyepiece of a telescope or through an optical finder! For more information about observing the Sun with a telescope, read the instructions for the telescope. Avoid accidentally bringing the Sun into the field of view of the telescope. Even a glimpse of the Sun can damage your eyesight.
Mercury
When to observe Mercury
Mercury has a reputation among observers as an "elusive planet". The fact is that among all the planets, the duration of its visibility is the shortest. Since Mercury does not move far from the Sun in its apparent movement across the sky, the inhabitants of the middle northern latitudes (Russia and the CIS countries, Europe, England, the USA, etc.) do not have the opportunity to see the planet in the dark. In contrast, Southern Hemisphere observers sometimes have the opportunity to capture Mercury after astronomical night has fallen.
The most favorable periods for observing Mercury are at the moments of its greatest elongation (removal from the Sun), and when the planet is at its greatest height above the horizon during sunset or sunrise. In the middle northern latitudes, such moments occur in the spring during the period of eastern elongation, when Mercury is visible in the evening, or in the autumn periods of its western elongation, when the planet is visible in the morning.
Mercury observations
Most likely, the first observation of Mercury will disappoint you a little. Compared to Jupiter, Saturn and the Moon, the planet is, to put it mildly, unattractive. Mercury is a planet for sophisticated observers who like to set themselves difficult tasks and strive to achieve great results.
Moreover, many experienced astronomers have never observed Mercury. But if you like to spend hours looking at dim and unremarkable galaxies, perhaps Mercury will be a new, exciting fun for you.
Observations of Mercury with the naked eye or with binoculars
Contrary to popular belief, Mercury is fairly easy to spot in the sky with the naked eye. As a rule, the chances of success are quite high if you look for a planet within a week before and after its greatest elongation. They increase significantly if the atmosphere is calm and observations are not hindered by tall buildings and urban smog.
In the spring, during the period of evening visibility, Mercury is visible to the naked eye half an hour after sunset, not high above the western part of the horizon. Depending on the terrain and the transparency of the atmosphere, the planet can be observed for about an hour in the twilight sky. Similarly, in the fall, when morning visibility sets in, Mercury can be seen 30 minutes after its rising and contemplated with the naked eye for an hour until it disappears in the rays of the rising Sun.
In favorable periods, the brightness of Mercury reaches -1.3 magnitude, which is only 0.1 less than that of Sirius, the brightest star in the earth's sky. It is worth noting that the low altitude above the horizon and, as a result, a thick and seething layer of air that stands in the way of light from the planet, make Mercury twinkle, like the rest of the stars. Many observers note the presence of a pink or pale pink tint to the planet - look out for this on your next observation of Mercury.
It is much easier to view Mercury with binoculars, especially in the first minutes after sunset, when the sky is still quite bright. Of course, it will not be possible to consider the phases of the planet with binoculars, but nevertheless, this is an excellent tool for searching for a planet and observing such beautiful phenomena as the convergence of Mercury with other planets, as well as with bright stars and the Moon.
Telescope observations of Mercury
As a rule, Mercury is available for telescopic observations for five weeks around the periods of its best visibility. But it is immediately worth mentioning that the observation of Mercury is not an easy task. As mentioned above, the low position of the planet above the horizon creates obstacles for its observation. Get ready for the fact that the image of the planet will constantly “sausage”, and only in rare moments, for a split second, the picture calms down and allows you to consider some interesting details.
The most obvious feature is the phases of Mercury, which can be easily seen with an 80mm telescope. True, for this it will be necessary to accelerate the magnification of the telescope to at least 100x. Near the maximum elongation, i.e. the best time to observe the planet, the visible disk of Mercury is illuminated by 50% (half of the disk). It should be noted that it is almost impossible to consider the phase when the planet is illuminated by less than 30% or more than 70%, since at this time Mercury is too close to the Sun.
If it is not so difficult to discern the phases of Mercury, then distinguishing the details on its disk is not a task for the faint of heart. There is a lot of conflicting information about the observation of various dark spots on its surface. Some observers report that they can see details in medium-sized telescopes, while others do not see anything on the planet's disk. Of course, success depends not only on the size of the telescope and its optical qualities, but also on the experience of the observer, as well as on the observation conditions.
Sketch. Dark details on the surface of Mercury. Telescope ShK 8"
Near the moments of the greatest elongation of Mercury, in a 100–120 mm telescope, under good atmospheric conditions, one can see slight darkening along the terminator line. However, it is quite difficult for an untrained eye to see the finest details on its surface, so experienced observers in this case are more likely to succeed.
With a telescope with an objective diameter of more than 250 mm, one can try to discern large darkenings of the surface far from the terminator. This exciting and extremely challenging activity can be a good test of your observational skills.
Venus
When to observe Venus
Venus is more accessible for observation than Mercury. Despite the fact that, like Mercury, Venus does not move far from the Sun, the apparent angular distance between them can reach 47 °. During the period of optimal visibility, Venus can be observed for several hours after sunset as the "Evening Star" or before sunrise - as the "Morning Star". Inhabitants of the Northern Hemisphere best time for observations falls on the eastern elongation, when the planet can be observed on spring evenings until midnight.
During periods close to the eastern or western elongation, the planet is located high above the horizon and has a high brightness, which favorably affects the observation conditions. As a rule, the duration of the best visibility is about a month.
Venus observations
Observations of Venus with the naked eye during the daytime
Most easy way observing Venus with the naked eye is to find the planet during its sunrise in the morning sky and keep it out of sight after sunrise as long as possible. In favorable periods of visibility and in the presence of an ideal state of the atmosphere, Venus can be kept out of sight for quite a long time.
The chances of success increase if the Sun is blocked by an artificial or natural barrier. For example, find a convenient place so that a tall tree or building can obscure the bright Sun, but does not cover the planet. Naturally, daytime searches for Venus should begin with accurate information about its position in the sky and its distance from the Sun. Such data can be obtained using any planetarium program, such as StarCalc.
Of course, it is quite difficult to see in the daytime sky a barely noticeable tiny patch of light, almost not distinguished from the surrounding background, which is Venus. However, there is one trick that can help catch this ghostly glow: when starting to search for a planet, you should first look at the distant horizon for a while, and then direct your gaze to the supposed place in the sky where Venus should be located. Since the eyes have the ability to maintain focus for a short period of time (in this case, focusing to infinity), your chances of seeing the planet increase.
Observations of Venus with binoculars
Binoculars are an excellent tool for finding Venus and making simple observations of it. Thanks to the large field of view of the binoculars, it becomes possible to observe the approaches of the planets to each other and to the Moon. Large astronomical binoculars - 15x70 and 20x100 - are quite capable of showing the phases of Venus when its visible disk is more than 40 "".
It is much easier to find Venus with binoculars during daylight hours. But be careful, even accidental hit The sun in your field of vision can damage your eyes, leading to complete loss of vision! The search for Venus is best done in good weather, when the sky is blue and distant buildings are visible on the horizon, which indicates a high transparency of the atmosphere. As a guideline when searching for a planet, you can choose the Moon, which is usually easily visible in a bright sky. To do this, in advance, using the planetarium program, determine the day and time when the Moon and Venus will be at a short distance from each other and, taking binoculars with you, go hunting.
Phases of Venus. Photographer Chris Proctor
Telescope observations of Venus
Daytime observations of Venus
Even in a small telescope, the dazzling radiance of Venus reduces the overall contrast of the image, making it difficult to see its phases, and also nullifies all efforts to discern the finest surface details.
One way to reduce the brightness of the planet is to observe it during the daytime. The telescope allows you to observe Venus in the daytime sky almost all year round. Only for two weeks before and after its upper conjunction, the planet is not available for observation due to its excessive proximity to the Sun.
Owners of Go-To telescopes can easily point their telescope at Venus using the Sun alignment method. How to do this is described in detail in the user manual of the telescope.
Another way to find Venus is to use a telescope on an equatorial mount that has setting circles. To do this, carefully align the mount, then point the telescope at the Sun, observing the necessary precautions (use a filter specially designed for viewing the Sun or project the image onto a sheet of paper). Then align the coordinate circles according to the pre-calculated equatorial coordinates of the Sun (Ra and Dec). The exact coordinates of the Sun and Venus at a given time can be calculated in advance using the planetarium program. After aligning with the Sun, slowly begin to move the telescope tube until the coordinates on the setting circles match those of Venus. Using the search eyepiece, look through the telescope and find the planet. It should be noted that it is much easier to view Venus if you carefully adjust the focus of the telescope to distant objects in advance.
Once the planet is found, a higher magnification can be applied. An orange or red filter can be useful as it can increase the contrast between Venus and the sky background, as well as bring out the subtle details of the cloud cover. In a period close to inferior conjunction, Venus looks like a narrow crescent. At such moments, you can notice the appearance of the so-called horns of Venus, which outline the disk of the planet with a thin light border. This phenomenon is caused by the scattering of sunlight in the planet's atmosphere.
A typical view of Venus through a small telescope. Sketch by Evan Bruce
Night observations of Venus
Despite the fact that daytime observations of Venus have several advantages, many amateur astronomers prefer to observe the planet in the twilight or night sky. Of course, at this time of day there are no problems with finding a planet in the sky, which is an obvious plus. However, there are plenty of downsides as well. As mentioned above, the main enemy of the observer is the dazzling brilliance of Venus, which prevents the detection of the finest details in the planet's cloud cover. True, this disadvantage can be overcome by using a polarizing filter with a variable density.
Another disadvantage is the small height of the planet above the horizon. As a rule, even during the best periods of visibility, at night, the height of Venus above the horizon does not exceed 30°. And as you know, it is desirable to carry out observations of any object when its height is more than 30 °. At this altitude, the negative effect of the atmosphere on image quality is minimized.
In general, speaking about the observation of Venus and taking into account the peculiarities of its visibility, this bar can be lowered. But it should be borne in mind that observations of the planet during the period when its height above the horizon is less than 20 ° are not desirable.
Observation of dark patterns in the clouds of Venus
Often, the disk of Venus appears to the observer uniform, grayish-white and without any details. Sometimes, at good conditions observations, one can notice a darkening along the terminator line. Even more rarely, some astronomy lovers manage to see dark formations that have bizarre shapes. What affects the visibility of details? At the moment there is no clear and unambiguous answer. Most likely, a combination of factors: the conditions of observation, the quality of the equipment, and the peculiarities of vision. Let's take a closer look at the last one.
Decades ago, it was suggested that some observers have eyes that are more sensitive to the ultraviolet spectrum, allowing them to see the dark bands and formations on the planet. This assumption was subsequently confirmed by photographs taken in the ultraviolet spectrum, which showed the presence of details not visible in ordinary photographs. Again, the self-deception of the observer should not be discounted. The fact is that dark features are extremely elusive - it is easy to convince yourself of their presence just because you expect to see them.
It is also difficult to answer the question about the minimum telescope required to observe the details of the cloud cover. Some observers claim that they see them in 100-mm telescopes, others fail to see them even in larger ones. Some observers manage to see the darkening with a blue, violet, or yellow filter. So no matter what equipment you have, keep trying to find interesting features, train your eyesight, and luck will surely smile at you.
There is the following classification of dark features:
Tape. Dark, parallel stripes. They run perpendicular to the edge of the horns.
Radial. Dark stripes running radially from the subsolar point (the place where the sun's rays hit at right angles).
Wrong. They have a fuzzy shape, can be either elongated or almost straight.
amorphous. Chaotic darkening, without form and not amenable to any description.
White (bright) spots on Venus
Sometimes it is possible to observe bright spots near the poles of the planet. The so-called "polar spots" can be observed for several weeks and are usually characterized by a slow appearance and an equally slow disappearance. Often spots appear near the South Pole, less often near the North.
Sketches of Venus in a 100mm reflector. Dark and light formations and irregularities of the terminator are visible.
anomalies
Schroeter effect
The so-called Schroeter effect consists in delaying or advancing the onset of the moment of dichotomy (phase 0.5) by several days relative to preliminary calculations. Observed in the lower planets (Mercury and Venus). The reason for this phenomenon lies in the scattering of sunlight along the terminator of the planet.
Ash Light
Another interesting illusion occurs when Venus has a narrow crescent phase. Sometimes during these periods you can notice a slight glow of the unlit part of the planet.
Contour roughness
Combinations of dark and bright details, which are more pronounced near the terminator line, create the illusion of unevenness. This phenomenon is difficult to see visually, but it usually shows up well in photographs of Venus. The planet becomes like a piece of cheese, as if neatly gnawed by mice from the edge (near the terminator).
Seeing this planet at dawn in the glow of the dawn, the Romans called it Lucifer, which means "shining." In the evening, when she stood out with her brilliance against the background of the sunset, she and Vesper, that is, the "evening star." In fact, we are talking about the same celestial body - the planet Venus, for many centuries in a row, because of the amazing radiance, people associated Venus with beauty and love, but today, thanks to modern probes, we know that this is a terrible world in which not a single person would not have lived even a fraction of a second. This is a place where the highest temperatures and monstrous pressure reign (92 times higher than the earth), and an extremely dense atmosphere is oversaturated with carbon dioxide, which is completely unsuitable for life. In a word, Venus is much more like Dante's hell than paradise.
HOT PLANET
When viewed with the naked eye, Venus is striking in its brightness, thanks to which it has always been considered a symbol of beauty. But now we know that this idea has little to do with the realities of the planet itself. Venus hides its secrets under an insurmountable thickness of the atmosphere, which does not allow any optical instrument to penetrate to its surface. In the lower layers, the air is almost motionless and is under such pressure, which on Earth is observed only in the ocean depths.
Hotter than Mercury
The Venusian atmosphere, rich in carbon dioxide, which causes the greenhouse effect, has led to a growing warming of the entire planet and the establishment of a truly hellish temperature. Venus is even hotter than Mercury, despite being much closer to the Sun. On the entire surface of Venus, the temperature exceeds 440 ° C also because the atmosphere not only accumulates heat, but also distributes it to the poles and to the night hemisphere.
The dimensions of Venus are comparable to those on Earth: its diameter is only 650 km smaller than the diameter of our planet. But the appearance of Venus is completely different. There is no liquid water there due to the strongest heating. As for the surface, its study with the help of a radar showed that it is rather flat: the height difference on 65% of the territory does not reach even 2 km.
Incredibly long day
Due to the continuous layer of clouds, atmospheric conditions are almost the same on the entire surface of Venus, but if this layer were not there, we would observe a picture that is very different from the earth. Since Venus' axis of rotation is practically devoid of tilt, there are no seasons on this planet, and the heat received by different areas depends only on their latitude. If a Venusian year of 224.7 Earth days doesn't seem so long, then what about the Venusian days, which seem to be just endless? The fact is that Venus makes a full rotation around its axis in 243 Earth days, that is, longer than its year! Therefore, a solar day on it lasts 116.7 Earth days. Don't be surprised: Venus is in a reverse rotation, that is, it rotates in the opposite direction from the normal movement of the planets in the solar system.
HOW TO RECOGNIZE VENUS IN THE SKY
It is difficult to confuse Venus with other celestial bodies, since in brightness it is second only to the Sun and the Moon. As for the maximum brightness, it is -4.4 m. The light of the planet is so bright that it forms shadows and faint reflections on the surface of the sea. With a cloudless sky, Venus can be seen even in broad daylight, provided that it is at a sufficiently large angular distance from the Sun. So finding the second planet of the solar system in the sky is not difficult at all. It should be borne in mind that Venus is visible only before dawn and at sunset.
Why does she shine so bright?
The brightness of Venus is not due only to the fact that it is close to the Sun. The real reason is its albedo, that is, the ability to reflect light coming from the Sun. Venus has the highest albedo of any planet in the solar system. The atmosphere of Venus reflects two-thirds of the sun's light. All this proves that the greenhouse effect is indeed powerful on Venus, given the amount of energy absorbed by the planet.
Elongations and connections
Even in ancient times, people noticed that Venus and Mercury move differently than other planets. This feature remained a mystery until the discovery of the heliocentric system: it helped to explain the strange movement of Venus and Mercury by the fact that the orbits of these two planets are inside the earth's orbit. Because of this, when viewed from Earth, the so-called inner planets seem to zigzag around the Sun, from which they never deviate by a large angular distance. The most favorable periods for observing these planets are called "maximum elongations". They correspond to the moment when the planets move away from the Sun to the greatest angular distance. In particular, when Venus is at its maximum elongation, it moves away from the Sun by an angular distance reaching 48 °, and it is visible in the sky almost 4 hours after sunset (at eastern elongation) or 4 hours before dawn (at western elongation). When the maximum elongation is completed, the angular distance between Venus and the Sun begins to decrease, and the periods during which the planet can be observed in the sky become shorter and shorter. When Venus finally reaches conjunction, observation becomes almost impossible due to its proximity to our star.
BRIGHT BUT MISTY
When viewed through your telescope, the planet, which the ancient Greeks dedicated to the most beautiful of goddesses, looks like a red-hot disk of white-gray color, while its circumference will almost never appear clear due to the change of phases. Venus is considered one of the most difficult planets to observe through a telescope. And the point is not at all the difficulty of pointing the telescope in the right direction. On the contrary, Venus is very bright! The problem is that the dense layer of clouds enveloping the planet makes its observed disk insufficiently contrasting. Only with the help of some tricks can you see at least fleeting details.
Phases like the moon
Like our Moon, Venus shows us either a crescent or a convex disk. The disk of Venus is visible in its entirety only when the planet is located near the superior conjunction. However, in this case, observation of it is complicated by small angular dimensions (at this time the planet is at its maximum distance from us) and too small an angular distance from the Sun.
The same difficulty arises when Venus reaches inferior conjunction. But in this case, the planet will turn its unlit hemisphere towards the Earth, and therefore we will be able to observe only a crescent, although it reaches an impressive angular size (about 60 °).
daytime observations
To see any details on the surface of Venus, you need to increase the contrast and also reduce the blinding effect from the excessive brightness of the planet, for which it is recommended to use color filters, such as the moon filter that comes with your telescope. And to increase the contrast, it is best to observe at dusk or even during the day. This will soften the difference in brightness between the planet's disk and the celestial background, and the pale blurry spots on the surface of Venus will appear somewhat clearer. Daytime observation, among other things, provides a noticeable advantage - the ability to point the telescope to a greater height above the horizon (the fact is that the insignificant angular distance separating Venus from the Sun leads to the fact that the planet reaches its greatest height above the horizon during the day). This entails a reduction in atmospheric turbulence and, accordingly, an improvement in visibility. On the other hand, in bright daylight, finding a planet in the sky is not easy. This difficulty can be overcome by setting the celestial coordinates of Venus on the mounting circles that came with your telescope.
Not at all twins
Why on Venus, whose size, mass and density are so similar to those of the Earth, atmospheric conditions formed so different from the Earth? The answer probably lies in the difference in distance from the Sun. Venus is located closer to our star, and therefore was exposed to higher temperatures, due to which liquid water disappeared on the planet and two gases were released that create a powerful greenhouse effect: water vapor and carbon dioxide. While on Earth a fairly large amount of carbon dioxide (CO2) is concentrated in carbonaceous rocks, on Venus all carbon dioxide remains in the atmosphere.
As for water vapor, ultraviolet solar radiation very quickly decomposed it into hydrogen, which immediately dissipated in space, and oxygen, which later became part of the surface rocks. Therefore, today its concentration in the Venusian clouds is about 0.01%, that is, it is minimal.
On Earth, water vapor is responsible for the formation of clouds. And on Venus, clouds are more like smog. They appeared as a result of a chemical reaction involving sulfur compounds, such as sulfuric anhydride, in the atmosphere formed under the influence of volcanic eruptions.
Desert or swamp?
Many past astronomers have tried in vain to map the surface of Venus based on shifting dark features, most likely caused by atmospheric events. AT late XIX century, two theories were the most popular: the first represented Venus as an exceptionally wet world, consisting of endless swamps inhabited by giant plants and water creatures. The second theory described the planet as a scorched desert with incessant winds that raised sandstorms. By 1950, the mystery had been solved through the use of new research technologies. On the one hand, the study of the radio emission of Venus made it possible to learn that extreme weather reigns there. high temperatures, and on the other hand, astronomers who studied the atmosphere of the planet, such as, for example, the French scientist Oduan Dollfus, were able to determine its chemical composition.
RESEARCH
On December 14, 1962, the American probe "Mariner-2" flew near the orbit of Venus and officially opened the era of space exploration of the planets of the solar system. If NASA used the Mariner missions to study Venus from the outside, then the very ambitious goal of the Soviet missions was to lower the probe to the surface of the planet. Despite the monstrous atmospheric conditions, already in 1970, the Venera-7 probe was able to transmit information from the Venusian surface for as long as 23 minutes until it broke under the influence of incredible heat (the probe recorded a temperature of 475 ° C).
Northern hemisphere of Venus
"Magellan" and the geography of Venus After completing the Mariner missions, NASA decided to rely on probes that act like "space submarines", that is, capable of probing the Venusian surface from above using radio signals, whose reflected echo was supposed to serve to create a map of this planet . Following the first successes of the Pioneer Venus probes, the geography of Venus finally ceased to be a mystery thanks to long work the Magellan probe, which began on August 10, 1990. By the time Magellan completed its research activities, it had mapped 98% of the surface of Venus, most of which turned out to be flat. The artificially colored image obtained by the probe shows that only 8% of the planet's territory rises above the surface by more than 2 km in height. There are three small continents on the surface. Three continental regions - Ishtar, Beta Region and Aphrodite - are separated by huge plains of basalt origin, often crossed by faults and folds.
"Venus Express"
In spite of progress made, the second planet of the solar system holds many more secrets. To answer the remaining questions, Venus was challenged by a new player. It's about the European Space Agency who launched the Venus Express interplanetary probe. The launch took place on November 9, 2005, and Venera Express reached its target on April 11, 2006. Having entered orbit around the planet, the probe began its work, and we received truly unique pictures of the Venusian atmosphere.
Observations from orbit showed the presence of an atmospheric vortex near the south pole, while analysis of the dark hemisphere revealed that the gaseous envelope surrounding Venus extends far beyond the limits known to date.
> How to observe Mercury and Venus
Mercury and Venus in the sky - how to observe the first planets from the Sun: choosing a telescope and filters, when to observe and where to look, photos of the planets, Venus in the afternoon.
Mercury and Venus seem to be the easiest planets to observe, because they are considered the neighbors of the Earth, located at a relatively close distance, and Venus was generally perceived in antiquity as the Morning and Evening Star, because it burned brightly in the night sky. However, it is important to know how to find Mercury and Venus and distinguish them from other objects. You should also understand how to choose and buy the right telescope in order to enjoy the view and even take high-quality photos of Mercury and Venus.
Mercury is the planet closest to the Sun. The distance between the Sun and Mercury is approximately 58,000,000 km. The planet's orbit is overly elongated. The length of a year on Mercury is 88 days. Around the planet there is a very rarefied atmosphere with a high content of helium. The pressure of such an atmosphere is 500 billion times lower than the pressure at the surface of the Earth habitual to man.
Venus is one of the most interesting objects in the starry sky, which is second only to the Sun and the Moon in terms of brightness. The planet makes a full revolution around the Sun in 255 days, and around its axis - in 243 days. This makes Venus the planet with the longest day in the solar system. The atmosphere of Venus is about 96.5% carbon dioxide and 3.5% nitrogen.
Tools
There are no significant differences between how to find mercury and venus in the sky. But there are a few tricks here that are worth learning. For example, observations of Venus will be ineffective if carried out with an achromatic refractor, which aggravates the image with impressive chromatism. This is especially noticeable because of the brightest shine of the planet. It's best to stock up on a Go-To or equatorial mount, as exploration of the lower planets is usually done during the day. That is why the use of the usual alt-azimuth mounts is virtually impossible here.
With visual surveys, it is almost impossible to see any details on the surface of Venus and Mercury, so you should not doubt the quality of optical telescopes. Modern planetary eyepieces - monocentrics and orthocentrics will help to correct the situation.
Do not forget about the set of color filters, which must contain dark red, red and orange filters, designed to increase the contrast of the planets during observations in the twilight or daytime sky. Violet and blue filters are used to visualize dark details on planetary disks.
Please note that during daytime observations of Venus or Mercury, you cannot look at the Sun through an optical finder or telescope eyepiece! Avoid even accidental entry of the Sun into the field of view of the telescope. Even one second misstep can cost you your eyesight!
When to observe Mercury
It is not for nothing that Mercury is called the elusive planet, because the duration of its visibility period is shorter than the rest of the planets. At the same time, Mercury moves in close proximity to the Sun, so residents of the northern regions of Russia, Great Britain, the USA and the Scandinavian countries cannot see it at night. And astronomers from southern countries can observe Mercury after the onset of astronomical night.
It is best to observe Mercury at the moments of its maximum elongation, when the planet moves away from the Sun at a considerable distance and occupies the highest point above the horizon during the morning or evening dawn. In northern latitudes, such periods occur in spring, when Mercury is visualized in the evenings, or in autumn, when the planet is observed early in the morning.
Mercury, Venus and Jupiter in the evening sky
Mercury observations
For novice astronomers, observations of Mercury can be a little disappointing. Appearance planets is not very attractive, especially compared to Saturn, Jupiter or the Moon. That is why only a sophisticated observer who is not afraid of difficult tasks can appreciate the true beauty of Mercury.
At the same time, not every experienced astronomer has observed Mercury at least once, since many hours of looking at dim and boring galaxies attracts only the most enthusiastic researchers.
Where to find Mercury?
Where to look for Mercury in the night sky? Well, Mercury can be easily found in the sky with the naked eye. This is usually done within a week before and after its maximum elongation. It is better if the atmosphere at this time is quite calm, and there is no urban smog or high-rise buildings around. In the spring evenings, Mercury can be seen for half an hour after sunset. Then the planet is located above the western part of the horizon. In the twilight sky, the planet can also be visualized, but here the transparency of the atmosphere and the terrain have their value. In the autumn months, during the period of morning visibility, Mercury can be seen half an hour after its rising. The planet is visible to the naked eye for 60 minutes, then it disappears into the sun's rays.
On good days, the brightness of Mercury is -1.3 magnitude. This is 0.1 lower than the parameters of Sirius, the brightest star in the night sky. Note that the proximity to the horizon and the thick, turbulent layer of air in the light path from the planet make Mercury a twinkling star with a pink or pale pink hue.
The task of observing Mercury is made easier if you have binoculars. It is especially easy to find it just after sunset in a bright sky. Of course, with the help of binoculars you will not be able to see the phases of Mercury, but this is an excellent tool for searching for it and studying such phenomena as approaching stars, other planets, the Moon.
Telescope observations of Mercury
Telescope observations of Mercury are possible for about five weeks before and after the period of its maximum visibility. However, he will immediately say that the study of this planet is an extremely difficult task. As noted above, the low position of Mercury above the horizon makes it impossible to fully explore it even with a telescope. The image of the planet is constantly distorted, calming down only at rare moments when the astronomer can see the most interesting details.
The main feature of Mercury is its phases, which you can study with an 80mm telescope. Of course, for this you need to increase the multiplicity of the device to 100x or more. During maximum elongation, the disk of Mercury is illuminated by the Sun by about 50%. And the phases at illumination less than 30% or more than 70% cannot be seen, because during such periods the planet is too close to the Sun.
A more difficult task is to study the details on the Mercury disk. There are many conflicting data about the nature of the tight spots on its surface. Some astronomers say that with the help of an average telescope they can perfectly explore the disk of the planet, others see nothing at all on the surface of Mercury. Of course, not only the quality of the telescope plays a role here, but also the conditions of observation, as well as the experience of the astronomer.
Under excellent atmospheric conditions, using a 100-120 mm telescope at the moments of maximum elongation of the planet, you can see small eclipses near the equator line. But an inexperienced explorer is unlikely to catch such fine details on the surface of the planet. And with a telescope larger than 250mm, you can explore large eclipses far from the equator. Believe me, this is a difficult but extremely exciting activity for training your observer skills.
When to observe Venus
Observing Venus is easier than Mercury, especially if you know where to look for it in the night sky. Although this planet, like Mercury, does not move a significant distance from the Sun, the apparent angular distance here can reach up to 47˚. During maximum visibility, Venus opens its disk for several hours after sunset, when it appears to the layman in the form of the Evening Star, or before dawn - in the form of the Morning Star. Northern Hemisphere astronomers are better off observing Venus at eastern elongation. On spring evenings, Venus is visualized until midnight.
During western or eastern elongation, it is high above the horizon, and its brightness allows observations to be made with minimal effort. Typically, the period of optimal visibility lasts one month.
How to find Venus with the naked eye during the daytime
The easiest way to observe Venus with the naked eye is to find it at the time of its morning sunrise. During periods of optimal visibility under good atmospheric conditions, Venus can be explored for quite a long time. You can make the task easier by blocking the Sun with a natural or artificial barrier: a high-standing tree, building or other object that will block the Sun, but not close Venus. Of course, daytime searches for Venus are impossible without information about its exact location. You can find out this information from any planetarium program.
Naturally, the observation of a small, almost imperceptible patch of light in the daytime sky is not an easy task. But there is a little trick here. First, look at the distant horizon for some time, and only then direct your gaze to the supposed area of the sky. This will keep your eyes focused on infinity and you can quickly find the planet you want.
Observations of Venus with binoculars
Binoculars are a great tool, both for searching and for elementary observation of Venus. A large field of view allows you to observe the approach of Venus with other planets and the Moon. Powerful astronomical binoculars 15x70 and 20x100 can also demonstrate the phases of the planet, when the visible part of its disk is more than 40”.
The search for Venus with binoculars is best done during the daytime. However, remember that even a short hit of the Sun in the field of view can deprive you of your eyesight! Explore Venus when the weather is fine, when distant buildings are visible on the horizon and the sky is deep blue. All this testifies to the excellent transparency of the atmosphere. Your reference point in the search will be the Moon, which is perfectly visible in the daytime sky. But predetermine the day and approximate time when the Moon and Venus will approach at a minimum distance. You can find out with the help of the planetarium program.
Telescope observations of Venus
Daytime observations of Venus
The dazzling brilliance of Venus reduces image contrast even in entry-level telescopes. This makes it difficult to observe its phases and does not allow you to see the details on the surface of the planet. However, there are several ways to reduce the brightness of Venus. First, observations of Venus are best done during the day. Moreover, you can do it throughout the year. The exception is two weeks before and after the upper conjunction of Venus with the Sun.
With modern telescopes equipped with the Go-To system, Venus can be easily located using the Sun alignment method. You can also detect a planet through a telescope on an equatorial mount with setting coordinate circles. Align the mount as closely as possible, and then aim the scope at the sun in a safe manner. After that, you should align the coordinate arcs with the equatorial coordinates of the Sun, and only then you can gradually move the tube, achieving the coincidence of the coordinates of Venus with the coordinates on the setting circles. You can also use a search eyepiece. Note that the search for Venus is facilitated by preliminary adjustment of the telescope focus to distant objects.
Once the search is successful, you can use increased magnification. Stock up on a red or orange filter to increase the contrast between the sky and Venus and bring out the subtle details of the cloud cover. At the moment of inferior conjunction, the planet is visualized as a narrow sickle. Then you can see the horns of Venus, which go around the planetary disk with the thinnest light border. This phenomenon is explained by the scattering of sunlight in the atmosphere of Venus.
Transit of Venus through the Sun
Night observations of Venus
Of course, daytime observations of Venus have a number of advantages, but some astronomers like to study it in the night or twilight sky. At such a time, there is no difficulty in finding the planet. But this plus is combined with some disadvantages. The main one is the dazzling brilliance that makes it impossible to see the finest details on the cloud cover of Venus. You can fight this problem with a special variable density polarizing filter.
The second disadvantage is the low position of Venus above the horizon. Even at the moments of maximum visualization at night, Venus does not rise above the horizon above 30˚. And all astronomers know that astronomical observations of any object are best done when it is at a height of more than 30˚. So Negative influence atmosphere on the image quality is reduced to zero.
Observation of dark patterns in the clouds of Venus
Most often, Venus appears to astronomers as a uniform gray-whitish disk without any details. However, under excellent atmospheric conditions, a dark zone can be seen along the terminator. Rare astronomers manage to consider some dark formations of a bizarre shape. What factors affect the visibility of details? Today this question remains unanswered. A number of factors play a role, including the quality of the equipment, the conditions of observation and the capabilities of the human eye.
About 30 years ago, the scientific community developed the idea that some people have eyes that are more sensitive to the ultraviolet spectrum. They are able to see dark bands and other formations on Venus. This idea was confirmed by ultraviolet imaging, which showed the presence of details that are invisible in traditional photographs. In addition, do not forget that enthusiastic astronomers are prone to self-deception. In fact, dark details are quite subtle, so it's much easier to convince yourself of their existence than to see them in reality.
It is also impossible to give an unambiguous answer to the question of the minimum power of a telescope for observing details on the surface of Venus. Some astronomers are able to see them in a 100-mm telescope, while others are unsuccessfully trying to do it in more powerful instruments. Some enthusiasts successfully use yellow, purple, blue filters. That is why we advise you to constantly try to look at the interesting features of Venus, train your eyesight and experiment with the power of the telescope.
At the moment, several groups of dark parts have been developed:
- Radial. Dark streaks radiating from a single subsolar point.
- Tape. Dark stripes parallel to each other. Perpendicular to the edges of the horns.
- Wrong. They have an indistinct shape.
- Amorphous. Darkening of a chaotic nature, without any form.
Bright white spots on Venus
If you know how to observe Venus in the sky, then in a number of cases on the planet you can see bright spots near the poles of the planet. These "polar spots" can be observed for several days or weeks. They gradually appear and also gradually disappear. More often they form at the south pole, less often at the north.
anomalies
Schroeter effect
The Schroeter effect is an advance or delay in the moment of dichotomy by several days (from preliminary calculations). It is observed near the lower planets and is due to the scattering of sunlight along the terminator line.
Ash Light
The illusion that Venus is visualized in the visage of a narrow sickle. In some cases, one can observe a slight glow of the hidden part of Venus.
Contour roughness
Combination of bright and dark details along the terminator line. This creates the illusion of uneven terrain. Visually, this phenomenon is quite difficult to notice. However, it is clearly visible in astrophotos. On them, Venus looks like a piece of cheese, gnawed by mice around the edges.
Instruction
Five were discovered in ancient times, when there were no telescopes. The nature of their movements across the sky is different from movement. Based on this, people have separated from millions of stars.
There are inner and outer planets. Mercury and Venus are closer to the Sun than Earth. Their location in the sky is always close to the horizon. Accordingly, these two planets are inner planets. Also, Mercury and Venus seem to follow the sun. Nevertheless, they are visible to the naked eye at the moments of maximum elongation, i.e. during the maximum angle from the Sun. These planets can be seen at dusk, shortly after sunset or in the wee hours. Venus is much larger than Mercury, much brighter and easier to spot. When Venus appears in the sky, no star can compare with it in brightness. Venus shines with white light. If you look closely at it, for example, with binoculars or a telescope, you will notice that it has different phases, like the moon. Venus can be observed in the form of a sickle, decreasing or increasing. In early 2011, Venus was visible for about three hours before dawn. It will be possible to observe it again with the naked eye from the end of October. It will be visible in the evening, in the southwest in the constellation of Libra. Toward the end of the year, its brightness and duration of the visibility period will increase. Mercury is mostly visible during twilight and is quite difficult to spot. For this, the ancients called him the god of twilight. In 2011 it can be seen from the end of August for about a month. The planet will first be visible in the morning hours in the constellation of Cancer, and then move into the constellation of Leo.
The outer planets are, respectively, Mars, Jupiter and Saturn. They are best observed during moments of confrontation, i.e. when the Earth is on the same straight line between the planet and the Sun. They can stay in the sky all night. During the maximum brightness of Mars (-2.91m), this planet is second only to Venus (-4m) and Jupiter (-2.94m). In the evening and in the morning, Mars is visible as a red-orange "star", and in the middle of the night it changes light to yellow. In 2011, Mars will appear in the sky in the summer and disappear again at the end of November. In August, the planet can be seen in the constellation of Gemini, and by September it will move into the constellation of Cancer. Jupiter is often seen in the sky as one of the brightest stars. Despite this, it is interesting to observe it with binoculars or a telescope. In this case, the disk surrounding the planet and the four largest satellites become visible. The planet will appear in June 2011 in the eastern part of the sky. Jupiter will get closer to the Sun, gradually losing its brightness. Closer to autumn, its brightness will begin to increase again. At the end of October, Jupiter will enter opposition. Accordingly, the autumn months and December are the best time to observe the planet.
From mid-April to early June, Saturn is the only planet visible to the naked eye. The next favorable period for observing Saturn will be November. This planet moves slowly across the sky and will be in the constellation Virgo all year round.
It is said that Napoleon was quite annoyed and angry when, one afternoon, during his trip to the Luxembourg Palace, the audience no longer looked at him, but at a star shining brightly in the daytime sky. This wonderful "star" was planet Venus.
This really does happen. It is known that in 1750, and also in Paris, Venus was visible in the daytime sky, which led the inhabitants of the city and the surrounding area into amazement and fear. In 1799, General Bonaparte, returning from the conquest of Italy, also saw a wondrous heavenly diamond above his head. Perhaps then he believed in "his star."
Camille Flammarion's Popular Astronomy says that in ancient times, Aeneas, returning from Troy, saw Venus shining at its zenith during the day.
And here is what another French astronomer, Francois Arago, wrote in the book “Public Astronomy”: “... In 1716, the London mob considered the appearance Venus day for something wonderful. This gave Halley a reason to calculate the positions in which the planet appears in its largest volume ... "
Visibility conditions for Venus
But really, what are the conditions for the visibility of Venus? Particularly during the day? The best visibility - evening or morning - when Venus is in. For Venus, the maximum value is 48° (in rare cases, 52°). However, not at every elongation Venus is visible in the sky well enough. The best evening visibility is in February, March, April. Morning visibility during western elongation is best in autumn: in August, September, October. It is at this time of the year that it happens to be observed during the day.
“... Then a sign will appear in heaven, the star is bright, standing above the church, shining all day ...” - we read, for example, in the Pskov Chronicle. It was Venus on August 25, 1331. On that date, she was in western elongation, that is, she was a morning star, and her brightness was approaching the maximum possible.
Venus is at its brightest approximately 36 days before and 36 days after inferior conjunction. At maximum brightness, the apparent stellar magnitude of Venus reaches minus 4.6m and more.
It happens that from the bright Venus, objects on Earth give a shadow.
Of the nine planets in the solar system, Venus largest albedo(reflectivity) - 0.77, which is probably due to the carbon dioxide atmosphere of the planet. But Venus also receives about twice as much sunlight as the Earth. That is why, even on Mars, Venus is the brightest light in the sky after the Sun and the Martian moons.
Now a few words about the phases of Venus. It is known that people with exceptionally sharp eyesight can see the phases of Venus even with the naked eye. Like, for example, the mother of the famous mathematician Gauss. He invited his mother to look at Venus through an astronomical tube, he thought to impress with an unprecedented sight: Venus in the form of a sickle. However, he himself had to be amazed.
The woman only asked why it is just with her eye that she sees a sickle turned in one direction, and through a telescope - in the other ...
The moon is known to be at its brightest during the full moon phase. But the maximum brightness of Venus falls on the period when about 30 percent of its surface is illuminated. This is about halfway between its greatest elongation and inferior conjunction.
The entire sequence, the entire cycle of its phases, Venus passes almost exactly 5 times in 8 years. In astronomical language, it sounds like this: 5 synodic revolutions of Venus are made in 8 years.
Indeed: the average synodic Venus period about 584 days. If 5 x 584 = 2920 days. And 8 periods of the Earth's revolution around the Sun - 8 x 365.25 = 2922 days. That is a difference of only 2 days! That is why every 8 years the conditions for the visibility of Venus are almost exactly the same. That is, every 8 years Venus appears almost exactly in the same phase, almost exactly in the same place in the sky.
The diameter of the planet in different phases is not the same: a narrow sickle is much larger in diameter than a full disk. The reason is that in different phases the planet is removed from us at different distances (from 108 to 258 million kilometers). In the immediate vicinity of the Earth, Venus faces us with its unlit side, so we never see its largest phase. A full disk is visible only from the greatest distance. Venus is brightest for us when its angular diameter is 40″ and the angular width of the sickle is 10″. Then it shines 13 times brighter than Sirius - the brightest star in the earth's sky.
That is why on ancient steles, seals, amulets, Venus was painted with 8 rays. And the number 8 was considered sacred by many ancient peoples.
The Babylonians at the end of the III millennium BC. e. there was a calendar based on an 8-year cycle. "8 great deities of the primordial time" knew the Egyptians.
In Homer's Odyssey, the eighth year is repeatedly mentioned as a turning point, bringing decisive changes. In Greece, it was generally believed that significant events usually occurred in the eighth year. Orestes takes revenge for the murder of his father, committed 8 years ago.
According to one version of the myth of Theseus, the Athenians sent a terrible tribute to the monster Minotaur to Crete every 8 years.
The Thracians called the festival in honor of the god of light and arts Apollo the “eight years”. And in ancient Thebes, a holiday in honor of Apollo was celebrated every 8 years. The ancient Aztecs held a festival of "absorption of water and bread" every 8 years. The laws of Moses contain an indication: "And you will sow in the eighth year ..." The list could be continued. But even this is enough to understand the significance of Venus in the life of ancient peoples! Venus was by far the first of the "wandering stars" that man singled out because of its conspicuous brightness.
However, initially the ancient peoples took the “morning and evening stars” for two different ones. Morning Venus was called Phosphoros by the ancient Greeks, and Lucifer by the Latins, both words meaning "carrying light."
BUT evening Venus called - Vesper (Hesper), that is, "west", "evening".
The word Vesper in modern times means "evening prayer" in many languages.