How To Use A Telescope With Glasses?

How To Use A Telescope With Glasses

Wearing glasses is like an evil necessary. You need them so much that you cannot stop using them although it comes with piles of problems. And it becomes a serious problem if you are into astronomy or a beginner in this area, doesn’t it?

Yes. I know exactly how that must feel like. Just when I became interested about this stuff, I thought that using a telescope with glasses was not a feasible idea. I was not even sure I could do this. Then, before I was about to give up, I decided to do a lot of research.

After doing lots of thorough researches, I got what I needed to know. I saw that it would not be the end for me if I could follow the findings from my researches. So here I am, passing them on to you if you are burdened with a pair of glasses like me.

Hope you find them helpful, Telescope Buddy!

Do You Use Glasses For Farsightedness Or Nearsightedness Or Both?

If your answer is yes, then this should not be a problem for you. Because using a telescope with glasses in any of these cases will not be necessary. To solve your sight problem, you can easily change the focus of your telescope to your advantage.

But What If You Have Astigmatism?

Now, this is a serious problem we are talking about. It cannot be fixed with the focus readjustment of the telescope and of course, you cannot get rid of your glasses. Because this problem demands a cylindrical correction. Before we dive into the solution, let’s get some ideas about astigmatism first.

When the shape of your eyes changes from how it should normally be, it is called Astigmatism. When you have astigmatism, your eyeballs become football-shaped, instead of round-shaped. 

As a result, what happens is that you cannot see things clearly due to your eyeballs’ shape. The deviated form of your eyeballs does not give the rays of light access to the main focus. So things become blurry to you.

If you have astigmatism, following the instructions below is a must for you. I think you will easily find what you need for using a telescope with glasses, just like I did.

1. Slight Astigmatism

With slight astigmatism, you can use your telescope even without your glasses only if you choose to see the Moon or planets like Jupiter that are located in a very distant place with a much higher magnification than others.

This is due to the very small shape of the telescope’s exit pupil. It lets a very tiny ray of light meet your eye and so astigmatism cannot affect you.

2. Severe Astigmatism

With severe astigmatism, using a telescope with glasses is mandatory for you. You can get more comfortable if you use an eyepiece specifically designed to provide Long Eye Relief (LER). It will help you enjoy telescoping into planets with higher magnification.

While using a telescope with glasses, you should choose a 16 mm eye relief. But remember that the larger the size of the eye relief, the better it will be for you. You can also buy a Barlow Lens for increasing the eye relief. It will enable you to use the eyepiece with a wider length and to increase the magnification simultaneously.  

Getting the right eye relief is an important factor. Because if you cannot get it right, it will fail to serve your purpose right. You can calculate the right eye relief for yourself by using this formula:

1 / Aperture of Eyepieces – Diameter of Pupil

Example: 1 / (25-7)   

On another note, it would be wise of you to consider coating on the spectacles. It would cause a reduction of reflection and give your eyes a touch of comfort.

Which One Is The Best Eyepiece For People Wearing Glasses?

There are a lot of eyepieces with different price ranges available in the market. But as you have glasses, you need a really good eyepiece to back you up with good support. In that case, you should seriously consider buying the eyepiece named the Explore Scientific 92. It is available in both 17 mm and 12 mm.

It even comes with a 20 mm long eye relief! While it is less expensive than the top quality ones, users find it excellent for its ergonomics. It is a little heavier than the ones for short eye relief. But with all that it offers, that should not make you worry.

What If I Do NOT Want To Use A Telescope With Glasses?

Well, no. I am happy to tell you that it is not totally out of the picture. There is an alternative to glasses: contact lenses. You can wear corrective contact lenses for your astigmatism while you are using a telescope.

Lenses have been told to bring about positive and significant changes in the experiences of many telescope users. So if you are tired of using a telescope with glasses on, why don’t you try lenses for a change (and some improvement)?

But you should keep this in your mind that lenses have a disadvantage as well. Wearing them all day can often make you feel too weary at night to start telescoping into the sky. Wearing glasses during the day and then putting the lenses on at night just before using the telescope can help you in this regard.

A lot of users prefer using glasses. So it is really up to you whether you want to use lenses or not. If you do change from glasses to lenses, remember that you may still need to use eye relief eyepieces. They usually start at 10 mm, so choose one which suits you the most.

What If It Is Not My Eyes? What If It Is the Eyepiece?

Usually, you should automatically know it if you have astigmatism. But you may have trouble with that if you have a mild astigmatism. In some cases, it is very much possible that the problem is not with your eyes but with your telescope’s eyepiece.

To be certain about that, you can carry out the simple test that I am going to describe now.

Choose a bright night to view the sky. Take an eyepiece with the lowest power for your telescope so that you can use the biggest exit pupil.

Move your head in different directions and see if there is any irregularity in accordance with the directions.

If there is any irregularity, it is because you have an eyesight condition, most probably astigmatism. And it is responsible for the irregularity, not your eyepiece. 

Another option available for you (Told you, the article would be very helpful!) is eyepieces with shorter eye relief that work with a specific level of power.

Now, How Will I Choose The Eyepiece For Using In Telescope Without Glasses Despite Having Astigmatism?

You can change your eyepieces’ power levels and increase them by using a Barlow Lens until the time comes when you can see things without any irregularity. To do this, you have to have several eyepieces for your own use.

If there is only one eyepiece with a large exit pupil, then you have to cover the aperture of your telescope with some pieces of circular papers for decreasing the focal ratio of the telescope’s increments.

The covered part of the aperture can be ½ or ¼ in ratio. For instance, if the focal length of an eyepiece is 42 mm, the exit pupil will be 6mm.

First, half the aperture and do it again to have an opening that is ¼ of the aperture.

You need to do this because this exit pupil works as the light diameter that goes from the eyepiece and comes straight toward our eye. And the dilated pupil of a person is 7 mm on an average. So you have to make sure that your exit pupil is not longer and not smaller than your own pupil.

So, to help you with your astigmatism, you have to have a 7mm image in your eyepiece and hence make your telescope’s aperture smaller. It will give you the longest length of focal without you having to wear glasses.

Also, note that if you don’t have astigmatism and the problem is with your eyepiece, you can still follow this method and solve it.

Final Words

This is all about using a telescope with glasses. Some of the ways, especially the ones without the glasses may seem complex to you. In that case, I would suggest you stick with your glasses and follow the relevant instructions. But if you prefer using a telescope with no glasses, then you have solutions in that regard as well.

I guess the article has been able to give you something to be optimistic about. Hopefully, you will be out there exploring the sky soon.

All the best!

Muntaseer

I have wondered how the Stars and Moons look like for many years. I’ve fallen in love with Cosmology since I was a boy. I am writing these articles to share my love for astronomy with you.

Recent Content