Observing the planets

The sky is a fascinating universe. Whether stars, planets or other objects, all its components are mysteries to be unraveled. In order to guide you in your observation, consult this guide to know the favorable moments and the information to know absolutely.

The entire solar system
Entire solar system

When can we observe the planets?

Defining the ideal moment to observe the planets depends on several criteria. Whether it is day or night, celestial events must be taken into account when observing the planets.

Daytime observation

Although it is customary to observe planets at night, it is possible to spot them during the day. Just aim for the moment when they are farthest from the Sun. Also, the size of the planets is an important criterion. If you have a telescope, know that the larger the diameter, the easier the location will be. For this, do not hesitate to consult the ephemerides and planetarium software. We can also talk about the location in relation to the meridian. It marks the highest point where the planet will pass during its movement.

Night observation

Obervation astronomique dans la nuit
The observation of the sky and the planets is done mainly at night

For nighttime observing, it is important to know when your planets are visible, since they are constantly in motion. If you are a beginner, it is recommended that you do some research to define the exact time of appearance of the planet you wish to observe. To determine the best viewing time, compare the onset period and peak visibility.

How to observe the solar system?

In the solar system, only5 planets can be observed with the naked eye. We will mention Saturn, Mercury Venus, Mars and Jupiter.
If you live in a rural area, it will be easier for you to observe the sky. Indeed,  light pollution makes it difficult to observe planets and stars.

How to find the planets in the sky easily?

To be certain that you are observing the correct planet, do not hesitate to use an updated star chart. Also, several specialized applications are available, we particularly recommend the mobile application Stellarium.

How to recognize and observe the planets in the night sky?

To recognize the planets in the night sky, you have to know how to look in the right place. With the naked eye, mobile applications will make your job easier and allow you to observe the nearest planets if the sky is clear . If you want to observe the planets with a telescope, orient it according to the position of the luminosity of the planet you are observing. For example, Venus being very silvery, it is the brightest and can function as a landmark. As for Mercury, it is distinguished by bright yellow against  red very remarkable for the planet < strong>March.

What to observe?

The planets of the solar system, as well as the two main stars are fascinating discoveries for any astronomy enthusiast.

The Moon, our natural satellite

Observation of the Moon
The moon, our natural satellite

By observing the moon, it is possible to better discover the only natural satellite of the Blue Planet and to understand the transformations it undergoes. The phases of the Moon can be explained by considering its interaction with the Earth and the Sun. You should know that the brilliance of “the star king of the night” emanates from the reflection of the sun’s rays. Its aspect changes in the following way from a fine crescent, towards a half-disc when it is at equal distance from the sun as from the earth. At the end of its trajectory, it is possible to see a complete disc which is also called full moon. This phase marks the location of the moon opposite the sun in relation to the earth.

During your observation of the moon, it will be possible to see dark spots: these areseas. These are traces on the surface of this star that mark the impact of huge meteorites dating back several billion years. This is why, from the earth, you will have the impression of perceiving the seas. In order to name them, you can acquire a Map of the Moon at a bookstore.

Another important phenomenon is related to the moon: the lunar halo. It is the result of a meteorological phenomenon similar to that of the solar halo. However, it manifests itself in the form of a brighter luminous disc. Compared to its diurnal opposite, it has a smaller diameter.

The Sun, our star

observation of the sun
The sun, our star

It is important not to observe the Sun directly as there is a high risk of burning your eyes. So, avoid aiming your telescope at the sun unless it has suitable protection. Sunglasses or welder’s mask with a grade below 14 are to be banned. Instead, ask your optician for advice, who will direct you to glasses made from Mylar sheets. There are also glass models that offer superior optical quality.

Venus or the Evening Star

Observation of Venus
Venus is visible after sunset and at dawn

Venus is the second planet in the solar system and is one of the 4 telluric planets in addition to Earth, Mars and Mercury. It is also the 6th largest planet. Its rotation is retrograde: this means that its direction of rotation is the opposite of the other planets. Indeed, the sun rises in the west and sets in the east on Venus. Its rotation is remarkably slow compared to the other planets since it takes 243 days. It is worth mentioning that Venus does not have a natural satellite.

Besides the Sun and the Moon, Venus is the brightest planet in the solar system. Like Mercury, the Evening Star is closer to the Sun than our planet. Its brilliance is such that it has been considered a UFO on several occasions. This phenomenon is explained by the reduced distance between Venus and the earth which allows a more intense reflection of the sun’s rays. It is possible to observe Venus in the evening or at the first light of the morning. It can even be visible up to 30 minutes after sunrise.

Also, as the sun sets in the west, don’t make the mistake of looking for Venus in the east. Indeed, if you are captivated by a remarkably bright planet, this would be Jupiter and not Venus.

Mars the red planet

Observation of Mars
Mars is easily recognizable thanks to its red soul

Mars is the 4th planet in the solar system. It is one of the telluric planets. It is 10 times larger than the Moon. One can note topographical analogies to the two planets in particular at the level of the craters. Compared to Earth, it has 10 times less mass and has similarities like valleys, rifts and volcanoes. In addition, it is home to the highest volcano in the solar system named Olympus Mons.

Although Mars is not as bright as Venus, it is recognizable by its reddish glow hence its name “Red Planet”. This color comes from the significant presence of iron oxide on its surface. It should be noted that Mars is farther from the sun than our planet. Despite its small size, you can observe it at different locations in the sky. Unlike Venus or Mercury which can be observed at sunrise or sunset, it is perfectly visible in the middle of the night. Since the planets are arranged on an axis that crosses the sky, it is possible to see Mars in different positions. Thus, it will be sometimes close to Jupiter, other times next to Saturn, and sometimes the Moon. Interestingly, so far Mars is the only planet, besides the Moon, from which photos of Earth have been taken.

Jupiter and Saturn, the gas giants

Observation of Jupiter
The giant Jupiter and its satellite Io

The planet Jupiter has a diameter nearly 11 times that of Earth (an approximate radius of 69,911 km). It also has a mass that is more than 300 times that of Earth. With a majority presence of hydrogen and helium, we can note that the composition of Jupiter is similar to that of the Sun. It is the 4th brightest planet in the solar system. This planet, which is distinguished by a yellow glow, is the 5th planet farthest from the solar star. You should know that Jupiter can be observed at any time of the day with a telescope or even good quality binoculars. You will see a large red dot or even the 4 largest moons of Jupiter: Europa, Callisto, Ganymede and Io. These Galilean moons lie on the equatorial plane of Jupiter. Indeed, they were observed by the Italian scientist thanks to astronomical glasses invented by him more than four centuries ago. In total, we can list more than 60 moons surrounding Jupiter although they are small in size and cannot be observed from your home. If you observe for several hours, you will find that the planet rotates. This movement is noticeable as the red dot representing it appears or disappears in the sky.

Observation de Saturne
The giant Saturn with its rings

Also,Saturn is another gaseous planet. Being further away than the rest of the planets in the solar system, it is considerably less luminous. It happens that during certain times of the year, Saturn is hidden by the Sun, which will make it impossible to observe it for several weeks. However, when the rings of Saturn are illuminated by the Sun, they are much more visible from Earth. Note that Saturn is not the only planet to have rings. This trait is common to other gas giants. Moreover, those of Saturn remain the most spectacular. Although their precise origin is not yet precisely defined, scientific theories claim that these rings date back between 10 and 100 million years. Research estimates that because the Saturnian ring system is unstable, the rings will inevitably turn to dust in several hundred million years. In order to locate Saturn more easily, know that it is recommended to consult an up-to-date sky map so as not to be mistaken.

Mercury, Uranus, Neptune and Pluto

Since Mercury is the closest star to the Sun, observing it can be problematic. As a result, this planet is only visible at sunset, if not exactly before dawn. To observe it, all you have to do is locate Venus: you will therefore only have to place Mercury closest to the Sun. Since two months in Earth days are enough to that Mercury goes around the Sun, it is observable alternately, either in the morning or in the evening. As for Uranus, it is unfortunately too distant to be able to be admired with the naked eye. For Neptune, the operation is even more delicate. You should know that this particular planet was first spotted by calculation before being visible using an astronomical telescope.

Observation of Mercury
Observation of uranus

For Pluto, now considered a “dwarf planet”, home observation is impossible. The only way to observe it is through a research telescope. This explains why its discovery is so recent: it dates from 1930.

Other sky objects to observe

In addition to stars and planets, other components of the Milky Way are to be discovered:


Observation de comète

Although they are visible to the naked eye, comets are an extremely rare phenomenon. Check the astronomical forecasts to see if there is one coming soon.

Shooting stars

Observation des Etoiles Filantes

If, while observing the sky, you see points of light accompanied by a trail quickly crossing the firmament, know that they are shooting stars. In reality, these are meteorites weighing less than 1 g. By penetrating the atmosphere of the earth, they heat up and ignite. This makes it possible to see several dozen  during a night observation.


Observation of eclipse

Whether partial or total, an eclipse is a captivating phenomenon. It theoretically occurs at intervals of 29.5 days and takes place when there is a new moon. Eclipses typically last two hours and 30 minutes. During a total eclipse, the sun is completely blocked by the moon, which is almost the same diameter as our star. When such an event occurs, you can perceive the planet Mercury more easily, very close to the Sun. In the case of an annular eclipse, you will observe that the size of the moon is smaller than that of the sun.