EP recommendations for glasses wearer

[jackal2477]

We just bought our first telescope (celestron nexstar 6se). My wife has astigmatism so will probably need to wear her glasses while viewing. What do you recommend for a 'starter set' of EPs? Also, should I get color filters or is that something that I should wait on?

[toshapetriji]

Hello welcome to SGL.

 

I have astigmatism and often view with my specs off, I'd advise trying an eyepiece and seeing if she has difficulty before seeking a solution to a problem she may not have. 

I recently bought my second filter and again I'd recommend waiting before rushing into buying sets of filters you may never use. Astronomy can be an expensive hobby so go slowly and just purchase what you need in the first instance.

[cletrac1922]

 

First of all welcome from Land Down Under

I wear glasses for reading, following cataract surgery several years ago, I go without them when viewing

EP have their own magnification, and your eyes adjust to them

I have filters as well, which very rarely use

At the moment you can use a red filter to observe the polar caps on Mars, as Mars will be closest to earth on the 6th October, than will be in the next 15 years

Lunar filter will dull the brightness when observing the moon, and highlight lunar features

John

 

 

 

 

[michael.h.f.wilkinson]

I have quite strong astigmatism, and must wear glasses while observing. I have found that for me any eyepiece with an eye relief of 16 mm or more works, and anything between 18 and 20 mm works well. This means that the 25 mm Plössls supplied with many scopes are fine. The 10 mm eyepieces supplied with many scopes aren't at all. Very long focal length Plössls become uncomfortable due to much too long eye relief, although that can be solved by good eye cups.

The TMB planetary EPs and their clones are very affordable, and fine for glass wearers. Among the clones the TS HR Planetaries get good reviews. The Vixen LV, NLV, and SLVs are more expensive, but clearly better. These can come up second-hand from time to time. At the high end there are the superb Tele-Vue Delos and Delite EPs, and Pentax XWs. 

 

[jackal2477]

Thanks everyone

[wookie1965]

BST Starguider have long eye relief and are very good eyepieces. 

[Starwatcher2001]

Another here with astigmatism. Whether it causes a problem or not can depend on the level of astigmatism and the focal length of the eyepiece (or more correctly, the size of the exit pupil of an eyepiece when in a particular telescope).  Longer focal lengths provide a wider beam of light, which is detected by a bigger area of your eye, and is more likely to show up problems with astigmatism. Shorter focal lengths give a narrower beam and therefore only use a smaller area of your pupil, which can mean astigmatism is not visible.

For me, anything longer than 17mm shows stars like lines without my glasses, but shorter ones don't. That means I can "get away" without glasses at higher powers and therefore don't need eyepieces with longer eye-relief.

If possible, give prospective eyepieces a try before buying (not easy in this climate I know), or assume that glasses are always needed.

[Oldfort]

I have astigmatism of 1.75diopters, and I find I don't need to wear my glasses (except for v low power daytime observing).  However you will likely need to adjust the focus between you and your wife's viewing.

BTW, the 6se is a great scope for visual observing, and small enough to take on holiday in a car - if we are allowed to go.

[Louis D]

Here's Tele Vue's table to help figure out if you need to wear eyeglasses at a particular eyepiece:

Exit pupil is simply the eyepiece focal length divided by the telescope's focal ratio while the astigmatism value can be read from your eyeglass prescription's CYL or cylinder correction value.  Basically, the more astigmatism you have, the smaller the exit pupil (higher power) you'll detect it in.  With my 2.0 diopters in my observing eye, I can easily see aberrated stars down to 1.0 to 1.5mm or so.  Below that, I find improved resolution wearing eyeglasses, but stars look okay.

Edited October 1, 2020 by Louis D

[Nyctimene]

Not cheap, but might be a lifetime investment:

https://www.teleskop-express.de/shop/product_info.php/info/p891_Tele-Vue-Astigmatism-corrector---0-25-dpt---DRX-0025.html

Stephan

 

[Louis D]

3 hours ago, Nyctimene said:

Not cheap, but might be a lifetime investment:

https://www.teleskop-express.de/shop/product_info.php/info/p891_Tele-Vue-Astigmatism-corrector---0-25-dpt---DRX-0025.html

Stephan

 

Except that astigmatism correction tends to change with age.  That, and Dioptrx won't fit on many eyepieces and still requires about 15mm of eye relief.

[Second Time Around]

On 02/10/2020 at 03:01, Louis D said:

Except that astigmatism correction tends to change with age.  That, and Dioptrx won't fit on many eyepieces and still requires about 15mm of eye relief.

It's not often I disagree with Louis, who's probably forgotten more than I'll ever know and has been particularly helpful to me regarding eyepieces that accept a Dioptrx. 

However, I prefer a Dioptrx to correct my astigmatism rather than wearing my glasses.  One of several reasons is that, as Louis has pointed out, prescriptions change.  In fact mine changes every year, especially the correction angle needed.  With a Dioptrx one can keep up with these changes (even in mid-yea) simply by rotating it.  I've also found that I need a 0.25 dioptre extra astigmatism correction at night compared with my daytime glasses.

Additionally, the Dioptrx corrector is made from glass rather than the plastic lenses in my specs and so is probably better corrected.  Certainly the coatings are likely to be better even than my expensive glasses.  I also don't want to risk scratching my glasses on an eyepiece (don't ask me how I know!).   

As Louis has pointed out, one still needs an eyepiece with long eye relief as a Dioptrx eats up about 8mm of this.  In practice I find I need about the same eye relief as using my glasses, despite choosing a frame design especially for telescope use.

Most Televue eyepieces accept a Dioptrx as can be seen from the following chart.  However ignore those with an asterisk as these have insufficient eye relief when used with the necessary adapter.   Go to https://televue.com/engine/TV3b_page.asp?id=214

Non-Televue eyepieces I know accept a Dioptrx (sometimes with an O ring) include :

 

Svbony 7-21mm zoom

Baader Hyperions including the zoom

Baader Morpheus

APM 24mm 65 degree

Many 68 and 82 degree Explore Scientific eyepieces - certainly my 28mm 68 deg does

Pentax XWs

Omegon 22mm 70 deg LER ( As Louis has previously pointed out the similar AF70, Omegon Redline SW, and TS-Optics Expanse WA versions with the screw-off eyecup all accept a Dioptrx, but not the Celestron Ultima LX or Olivon 70 versions with a twist up eye guard).

Vixen 22mm LVW (used only)

 

A search will reveal many others.  I simply won't buy an eyepiece that doesn't take a Dioptrx when I can benefit from one.  Luckily, there's a lot that will.

 

 

[Louis D]

5 hours ago, Second Time Around said:

One of several reasons is that, as Louis has pointed out, prescriptions change.  In fact mine changes every year, especially the correction angle needed.  With a Dioptrx one can keep up with these changes (even in mid-yea) simply by rotating it.

Yes, position angle is not a big deal with Dioptrx, but I was pointing out that you need to buy a new Dioptrx if your astigmatism diopter changes too much.  Sure it's slow, but mine has crept up from 0.5 to 2.0 diopters over 40 years.  I used to need mostly distance correction (0.75 diopters), but that has also crept up to 1.75 diopters.  I just wanted to point out that a Dioptrx might not be a once in a lifetime purchase for everyone.  Maybe once every 10 to 20 years or so, depending on your age.  Based on my own experience, I would hold off buying one around your mid-40s as that is when my prescription was noticeably changing year by year in both distance and astigmatism as presbyopia was also setting in.

[Second Time Around]

Good point, Louis.