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It is frustrating when you set up your telescope at night, then look and can’t see anything through it! Been there, done that.
The reason why you can’t see anything through your telescope can be caused by a few factors. You are doing something wrong, there is something wrong with your telescope, or it is a problem with the location where you observe the night sky.
In this article, I will go through all of it to help you troubleshoot your problem so you can fully enjoy your telescope and the night sky.
The basic problems.
Maybe you are a beginner, and it is your first telescope. In all of the excitement, you may be forgetting some simple checks.
- Be sure that all dust covers are removed from the telescope.
It seems silly, but even experienced astronomers (including me) sometimes forget to take off some dust covers or, in astrophotography case, remove the Bahtinov mask after focusing.
- Use the eyepiece.
You should know that all telescopes require an eyepiece in the focuser to give you the image. If you are looking into the hollow tube, you are definitely missing the eyepiece.
Telescopes come with a pair of eyepieces, so first, use the one with the highest focal length number. The higher the eyepiece’s focal length, the less magnification you have, meaning it is easier to find something. Then you can switch to the shorter focal length to get more magnification.
- Align your finderscope.
Every telescope has a small scope on the top called a finder scope. It helps to find objects in the sky because it has a much wider field of view. Usually, there is a cross inside or a red dot if it is a red dot finder.
You have to position the cross or a red dot on the object you want to look at through the telescope. But first, you need to align it. The best way to do that is to do it during the day.
Find some electric pole or any terrestrial object in the distance. Try to find it with the telescope by looking through the eyepiece first. Center it in the field of view and fix the telescope so it can’t move.
Then look through the finderscope and align it by turning the screw to hit the object with the cross or red dot you see in the eyepiece. And you are done, you aligned your finderscope.
Now, you should always see the same object that’s in the finderscope in the telescope eyepiece.
- The telescope is well out of focus.
Astronomy telescopes have a focuser. It is a tube that moves in and out of the telescope by using knobs on the base of the focuser. The travel of this tube can be pretty long.
Sometimes you are all the way in or all the way out, and even if you point the telescope at the bright object, you can’t see anything through it.
In this case, you have to play with the focuser knobs until you see some light slowly coming into focus. The best object is always the moon because it is big and bright. So point the telescope at the moon and try to focus.
Once you can focus on the moon, it should be ok for all other objects in the night sky. All you need to do when you point on dimmer and smaller objects are slight adjustments with the knobs on the focuser.
- You forget the Barlow lens in the focuser.
Barlow lens is a tool that will increase the magnification of the telescope by 2x, 3x, or even 5x. It is placed between the focuser and the eyepiece.
What can happen is you forget the Barlow lens in the focuser tube, put the eyepiece in it, and the magnification is so high and out of focus that you can’t see anything through the telescope.
So be sure there is nothing in the focuser before you install the eyepiece.
- Dew on the mirrors and lenses.
The temperature of the telescope, no matter the type and the outside temperature, is another factor why you have issues seeing anything.
If you plan to observe the night sky when it is colder outside and take out your warm telescope, there will be condensation on the lenses or mirrors immediately. This is the cause of your problem.
The best practice is to take the telescope out one hour before you want to start stargazing. The telescope will cool down to prevent forming condensation on the optical parts. The bigger the telescope, the longer it needs to cool down.
But temperature fluctuations during the night can cause the same problem. That’s why astronomers and especially astrophotographers are using special dew heaters. These heaters cover some parts of the telescope to prevent dew from forming on the lenses and mirrors.
Your telescope is out of collimation – Newtonian telescope.
If you have a telescope with a mirror instead of lenses inside, you have a Newtonian reflector. These telescopes need to be collimated before you can see anything.
Commonly, the mirrors are slightly out of the collimation, and in this case, you will see the object in the eyepiece, but you will not be able to focus on it, and it will be blurry. All you need to do is slightly adjust the mirrors.
But if it is pitch black in the eyepiece and you are 100% sure that the telescope is pointing at the bright moon, you have a bigger problem. The mirrors are way out of collimation. Now you have to fix it with some big adjustments to the mirrors.
We use tools to collimate reflecting telescopes. You are screwed without them, and you need to buy them. The most used tools are laser collimator and Cheshire eyepiece. If you want to learn how to collimate a telescope, read my article How To Collimate Mirrors On Newtonian Reflector.
Your location – the light pollution.
The last issue can be your location.
You set up the telescope, and everything is ok. You didn’t forget to remove the covers. The telescope is collimated, and the finderscope is aligned.
Let’s say you have a GoTo telescope, so you put in the object you want to see. The telescope slews and points to the target, but you see nothing. So you try pointing it to the moon, and everything is alright, and you can see it in the eyepiece. So you are now going back to the first object, and you still see nothing.
The problem here is light pollution. Especially, it is a problem when using the telescope in the big city. You can have the biggest telescope in the field, but in a highly light-polluted city sky, you are limited to only seeing the moon and some planets.
All other objects like galaxies and nebulae are so dim that without the proper dark skies, you can’t see them through the telescope.
This is the common problem people have, they buy a telescope to use in the city or other light polluted areas, and they are sad and disappointed that they can’t see anything through the telescope.
The problem is not the telescope but the seeing conditions because dark skies are the most important factor in stargazing. You can check the light pollution in your location on this map. The purple, red, and yellow areas are where you don’t want to use the telescope.
If you click on the map, the small popup window appears with the details about the location. The info you want to check is the Bortle class.
The Bortle scale has nine classes. Class one is the darkest sky available in the world, and class nine is the inner city skies. Here is the summary of all classes:
- Excellent dark-sky site
- Typical truly dark site
- Rural sky
- Rural/suburban transition
- Suburban sky
- Bright suburban sky
- Suburban/urban transition
- City sky
- Inner-city sky
Keep this in mind, and believe me, that under the Bortle class 1 and 2 skies, you don’t even need the telescope. It’s like being in space.