Can I Use My Telescope Through a Window? – NO and YES

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This is not a stupid question. As a kid, I was using my first telescope through the window of my room. It was not the ideal use of a telescope, and there are rules you have to follow to have a decent astronomy experience.

You can use the telescope through the window, but the window must be open, and the room temperature must be equal to the temperature outside. You also need to do a lot of planning because of the restricted field of view from the window.

So let’s dive deeper, and let me explain the rules you have to follow. 

Can you use a telescope through the glass of the window?

Even if you have a brand new and scratch-free window with the cleanest glass in the world, you should not use the telescope to look through it.

The glass on the windows is not perfect, and it will distort the light coming from the stars and deep sky objects. The result is a blurry or distorted image in the eyepiece.

The glass elements in the telescopes are manufactured to the highest quality, which is not the case for simple windows glass. 

The window will also block some light from the deep sky objects, and it can contain reflections from your room or the outside world.

The only exception when you can use a telescope through the glass of the window is using it during the day to observe the outside world or spy on someone:)

But even in this situation, you will get much better image quality if you open the window.

Can you use a telescope through the open window?

Using a telescope through the open window is not as simple as you think. You might have an even worse experience than looking through the glass of a closed window.

The problem is the heat haze or heat shimmer. It occurs because of the temperature difference in your room and the outside. The heat from the room will be escaping through the window, causing shimmer when you look through the telescope.

Heat Haze Shimmer

The same happens when you take your warm telescope outside in colder weather. The heat escaping from the telescope will prevent you from using it. First, you need to take it outside for some time to cool down before you can use it properly. 

It’s called “thermal equilibrium” or “thermal optimization”. This is a huge problem if you want to use the telescope through the open window. In the wintertime, it is not possible, just forget about it. Unless, you cool down your room to the same temperature as outside, which I am pretty sure you don’t want to do.

The only time you can get around might be in summer when you have equilibrium between the inside and outside temperature at night. Or at the locations where the warm temperature is the same all year round.

What are the limitations of stargazing through the window with a telescope?

You see, so far, it is quite challenging to use the telescope through the window, and it gets worse. You also have a limited view of the night sky through the window. 

Not only that, but the night skies are rotating, and are different in the summer and winter. Sadly the winter skies are the best for stargazing, and as you know from above, it won’t be possible to use the telescope from your room in winter.

Moreover, if you live in the city, you can’t see any deep sky objects through the telescope because of the light pollution. You are basically limited to only two types of objects- the moon and the planets.

Telescope type limitations through the window.

The other limitation is the actual telescope type you can use. You can only use telescopes on manual mounts for stargazing through the window. I recommend only the alt azimuth mount because they are simple to use and more suitable for this purpose.

You can’t use GoTo computerized mounts because you won’t be able to align them with the stars. You need access to the whole sky for this, which you don’t have through the window. 

Yes, you can move them with buttons on the hand controller without the star alignment, but this will become just an expensive feature without the GoTo capabilities.

Planning is essential.

Firstly, the moon and the planets are not always visible in the night sky. Secondly, you need them exactly in your field of view from the window. To sum it up, you need to do some planning.

The best way is to use astronomy software like Stellarium, where you can set the date and time and check what you can see from your location and heading.

My experience using a telescope through the window.

As I said, I used the telescope through the window as a kid and for some time a few years ago. I was living in an apartment without a balcony, and I was lazy to go outside.

I have even done some astrophotography, but nothing special, just a few pictures of the moon.

It is very challenging, and as an experienced amateur astronomer, my advice is against that. You won’t enjoy using the telescope with all the obstructions “window stargazing” brings as you would outside with access to the whole night sky.

Not to mention, the weather can destroy all the preparation and planning.

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