Watching The Sky Part II

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2. When to observe the sky?
You must first ask yourself several questions: what do you want to observe, at what time and at what time of the year? First obvious thing to do astronomy, it takes a clear sky with very few clouds, without mist or fog. If the grass is wet, for example, at the end of the day and it is quite cold, there is the risk of fog during the night and you will not be able to easily see the stars.

With the Sun it’s easier. If the sky is clear, you can observe it at any time of the day. The ideal is to observe it during the noon hour because its image will be little disturbed by the turbulence, the light of the Sun crossing a layer atmospsheric thinner than the morning or the evening. It also shines much louder at noon and gives more contrasting images.

To observe the Moon, the planets, the stars or the galaxies it is necessary to wait until the night. In reality these stars also shine during the day but the Sun is so bright in the sky that you no longer see them.
In our latitudes (40-50 ° N) it is preferable to observe the sky in winter, when the weather is dry and very cold because the sky is often more limpid than in summer. Moreover it is night very early, around 17h and in the morning it can still be night at 8h. In winter you have the opportunity to observe the sky much longer, before going to bed or early in the morning as well as during the weekend or holidays.

Enjoy the winter because it is during this season that you will be able to observe the most beautiful constellations: Orion, Lyre, Cygne, Scorpion without mentioning the constellations that are always visible like the Big Dipper or Cassiopeia and clusters of Known stars such as the Pleiades M45, Praesepe M44, the globular cluster of Hercules M13, the Great nebula of Orion M42 and the Andromeda galaxy M31. These are all objects to be observed that will give you a good reason to buy an atlas of the constellations. We shall return later to the constellations and all the stars that inhabit the universe.

3. What equipment should I use?
Observation of an eclipse of the Moon.
With the naked eye you can observe stars and constellations and it is also the only way to learn to recognize them by comparing what you see with the maps of a good atlas. You will also be able to observe shooting stars (meteors), artificial satellites, lunar eclipses such as the one shown on the right, polar aurorae, different phases of the Moon and possibly photograph them.

But if you want to observe the craters of the moon, planets or nebulae you have to use an astronomy instrument that will allow you to enlarge the image of the objects, as does the telephoto lens of a camera. You can choose between 3 types of instruments: the pair of binoculars, the astronomical bezel or the telescope.

At most the lens (the lens or the mirror) of the instrument is large at most it will be bright and at most the image will be brilliant. It is also necessary that its focal length, its length, is long enough if you want a big magnification. It is especially important to observe the details, the craters of the Moon for example, planets or small galaxies.

A pair of 10×50 binoculars grows 10x and has a 50mm diameter lens. This is the ideal place to start; Especially since you can also use it to observe nature. When observing an object in a pair of binoculars, I advise you to put your elbows on a table or to press the binoculars against a wall or a tree or else you risk moving and having difficulties to center and observe the binoculars, object. You can also install the binoculars on a tripod with an adapter; So there will be no risk of moving and you will be able to observe the sky in very good conditions.

Since the magnification of the binoculars is often very small (10x in our example), you will be able to observe vast fields of stars, even more extensive than those you would see in a small 60 mm bezel. Indeed, the bezel will grow louder and this will reduce the field of vision.

A pair of binoculars is therefore ideal for observing vast areas of the sky and ideally in a very clear place, such as a meadow or a region of altitude away from any light. Thus, while in the city it is impossible to see the Milky Way in the middle of summer because of the light pollution, in the Alps, in the Val d’Aosta for example around 1500 or 2000 m of altitude, you see as much d Stars or almost only on the photographs. It is a truly magnificent spectacle for which binoculars are all you need. Think about it for your holidays!

On the other hand, binoculars with a small diameter, the image of the stars remains very small. If astronomy fascinates you, observing planets or galaxies, I suggest you replace your binoculars with an instrument of larger diameter and longer focal length. You have the choice between astronomical telescope and telescope.
The astronomical telescope consists of a lens made of lenses whose purpose is to collect the light and concentrate it towards the eyepiece which ensures the magnification. The larger the focal length of the lens, the easier it will be to enlarge the image and the longer the lens focal length, the higher the magnification.

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