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Telescope Eyepieces for Glasses Wearers: a Guide with Photos

Posted by Ryan DeLange on

When choosing eyepieces for glasses wearers, there are a few things to keep in mind. 

The best telescope eyepiece for glasses wearers should have a long eye-relief, a minimum of 15 millimeters. Soft rubber eyecups that fold down or twist-up are also important as they help prevent the glasses from bumping on the hard surface of the eyepiece.

Deciding on the best eyepieces may also depend on other factors unique to you, such as your particular vision problems, what telescope you have, and of course, your budget. 

The importance of eyepiece eye-relief for glasses wearers

Telescope eyepieces for glasses wearers; the importance of eye-relief

If you want or need to use glasses when using your telescope, you need to make sure your eyepiece has the proper eye-relief.

Eye-relief is the furthest distance that a person’s eye can be from the eyepiece while still seeing the full field of view. If the eye is further away from this point, the viewer will experience ‘tunnel vision’ as part of the circular view is cut off.

To allow space for your glasses, most astronomers suggest an eye-relief measure of at least 15mm. For some, up to 20mm is even more comfortable. 

In general, eyepieces with longer focal lengths also have longer eye-relief. Therefore, you may be able to use your glasses with longer focal length eyepieces, even common, inexpensive ones (or the ones that came with your telescope). 

Below is a table with some common, inexpensive eyepiece lines. Notice the relationship between focal length and eye-relief.

Two Lines of Inexpensive Plössl Eyepieces and their Eye-relief Specifications

Green - suitable eye-relief for use with glasses

Red - not enough eye-relief for use with glasses

Approximate eyepiece focal length

Meade 4000 Super Plossl 1.25”

Eye-relief

Celestron Omni Plossl 1.25”

Eye Relief

6mm

Meade 4000 Super Plossl 6.4mm

5mm

Celestron Omni Plossl 6mm

5mm

15

Meade 4000 Super Plossl 15mm

11mm

Celestron Omni Plossl 15mm

13mm

32

Meade 4000 Super Plossl 32 mm

26mm

Celestron Omni Plossl 32mm

22mm

40

Meade 4000 Super Plossl 40mm

28mm

Celestron Omni Plossl 40mm

31mm


You can see that most common eyepieces of shorter focal lengths have eye-relief numbers that are too small to be used with glasses.

The good news is that some manufacturers create short focal-length eyepieces with longer eye-relief. They usually come at a substantially higher cost though. See the section below titled "9 Best Telescope Eyepieces for Glasses Wearers".

The importance of eyecups for glasses wearers

Good eyecups are important for all users, but especially for glasses wearers. Eyecups are a design feature positioned where your eye approaches the lens when viewing. It increases comfort and keeps stray light out.

fold-down eyecups for telescope eyepiece

Soft, rubber eyecups are best. This design protects the lenses on both your glasses and the eyepiece. It also allows you to rest your glasses on the cup and provides some ‘give’ as you find the right position for your eye.

Some eyepieces have eyecups that either fold down or twist up. They are designed so you can find a position that suits you, and they are useful for glasses wearers and non-glasses wearers. Generally, you would fold the eyecups down when using glasses. The Televue eyepieces listed below have a unique sliding and locking feature that allows you to adjust the cup to exactly where it's comfortable for you.

9 Best Telescope Eyepieces for Glasses Wearers

Below are 1.25” eyepieces that get kudos from glasses wearers. They have longer eye relief and suitable eye-cups.

Product Name

Eye-relief 

Type of eyecups

Field of View

Televue Delos Eyepiece

20mm

Adjustable slider

72°

Pentax XW Eyepiece

20mm

Screw-on

70°

Baader Morpheus 76º Eyepieces

20mm

Fold-down

76°

Vixen SLV Eyepiece

20mm

Twist-up

45-50°

Explore Scientific 82° Series Waterproof Eyepiece (6.5mm and up)

16.8-22mm

Fold-down

82°

Agena Starguider Dual ED Eyepiece

15.8-20mm

Twist-up

60°

Televue Delite Eyepiece

20mm

Adjustable slider

62°

Orion Stratus Wide-Field Eyepieces

20mm

Fold-down

68°

Baader 1.25" Hyperion Eyepiece

20mm

Fold-down

68°


When do you need to use eyeglasses with a telescope?

Near-sightedness or far-sightedness can be corrected by using the telescope’s focuser, so eyeglasses are not necessary. 

Still, some people with near or far-sightedness prefer to use their glasses even though they don’t need to. Much of astronomy consists of looking into the sky without the telescope - simply looking up or through the finder scope. It can be annoying to keep taking one’s glasses off just to look into the eyepiece. Plus, nobody wants to search around for misplaced glasses in the dark.

Astigmatism, on the other hand, cannot be corrected with the telescope’s focuser so wearing glasses is often necessary.

That being said, even people with astigmatism, don’t need glasses in every situation. To understand that, we need to understand exit pupil. 

Exit pupil is the diameter of the beam of light that enters your eye as you look into the eyepiece. The diameter depends on the combination of the eyepiece and the telescope. 

It can be calculated using this formula:

Eyepiece focal length (mm) / Telescope focal ratio = Exit pupil 

For example, the exit pupil created by a 10mm eyepiece in a telescope with a 1000mm focal length and 100mm aperture (f/10) would be calculated as:

10mm (eyepiece focal length) / 10 (focal ratio) = 1mm exit pupil

So, the exit pupil increases as you EITHER use longer eyepieces OR use telescopes with shorter focal ratios, like fast Dobsonians. 

Generally, a person’s astigmatism is not apparent with smaller exit pupils. Each person’s situation will be a bit different, of course, depending on the severity and attributes of their astigmatism.

The important takeaway here is that a person with astigmatism may be able to use shorter eyepieces without glasses. He may only need to wear glasses when using eyepieces with longer focal lengths, which remember, have longer eye-relief. 

So, it may be that more expensive eyepieces are not necessary at all. You may be able to use your short eyepieces without glasses because of the smaller exit pupil, and use your longer focal length eyepieces with glasses because the eye relief is longer. The best thing to do is to experiment. If you want some more exact calculations regarding exit pupil and astigmatism, here’s a good resource.

Using a Barlow lens with glasses

What if you want to use a short focal length eyepiece with your glasses, and you don't want to purchase an expensive one with long eye-relief? Using a Barlow lens makes this possible.

Let's say you have a 10mm eyepiece that you can't use with your glasses because the eye relief is too short. But, you have a 20mm eyepiece that is very comfortable for use with glasses. 

Adding a 2X Barlow lens with the 20mm eyepiece gives nearly the same optical results as using a 10mm eyepiece while maintaining the eye relief of the 20mm eyepiece. 

You may be concerned about a loss of image quality using a Barlow lens, but modern Barlow lenses have a negligible effect on the image. Also, it could be argued that using glasses has some negative effect on image quality due to light refraction caused by the lenses. So, any negative results from the Barlow may be offset by the fact that you don’t need your glasses.

So, that covers choosing an eyepiece for use with glasses. Let me know if you have any questions or if you have something to add.


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