Wearing glasses while observing

[Stuu]

Hi all. I just have a question regarding wearing glasses while observing. I currently have a fairly mild prescription for varifocals and get on fine without them when using my telescope. Is there a point where I might have to start wearing them or is it just down to personal preference? I was wondering whether I'll need to plan what eyepieces to use based on their suitability for glasses wearers. 

[globular]

Telescope focusing corrects for most problems in your eyes - except for astigmatism.  So if your glasses are correcting for that, and it is a relatively strong correction, you may need them at the eyepiece.

If you need correction you have two main options:

*  wear your glasses and pick eyepieces that have long eye relief.  How long vary from person to person - but around 20mm is a good guide.

*  get a dioptrix corrector and pick eyepieces that can take them.  e.g. https://www.firstlightoptics.com/tele-vue-eyepieces/tele-vue-dioptrx-astigmatism-corrector.html 

The other thing worth noting.... if you share observing with a friend or partner and one of you needs correction... then you should wear your glasses so that it is perfectly focused for both of you.  I add this because it's the situation I'm in.  My wife loves to look through the eyepiece but "can't be doing with the faff of focusing" so I set it up with my pretty good eyes and she observes with her glasses.

Edited September 2, 2021 by globular
typo

[Alan White]

If you get on witholut them and your present eyepieces you have done well.

Longer eyerelief is needed for glasses and caused me a serious churn in my eyepieces.

I find I cannot wear my varifocals at the scope due to the reading bit getting in the way,
so have distance only when at the EP.
That then causes grief reading star charts etc.

My reason was astigmatism only and liking double stars, i could not see the closer ones over my astigmatism.

 

 

Edited September 2, 2021 by Alan White

[Gfamily]

I generally wear my spectacles for observing, so I can call Mrs G over and she won't need to adjust the focus*

I use varifocals normally, but about 6 years ago got a pair of single vision spectacles for telescope use.

Last evening I used them for the first time in a while, and discovered the downside - I now can't see the handset clearly as my 'near' vision has deteriorated so much. Getting old would be a real pain if it wasn't better than the alternative.

* she always does, but that's fine.

[ScouseSpaceCadet]

1 hour ago, Stuu said:

Hi all. I just have a question regarding wearing glasses while observing. I currently have a fairly mild prescription for varifocals and get on fine without them when using my telescope. Is there a point where I might have to start wearing them or is it just down to personal preference? I was wondering whether I'll need to plan what eyepieces to use based on their suitability for glasses wearers. 

Afaik it's not easy to predict how much one's eyesight will deteriorate... I wear glasses for distance however in my early forties the middle age onset reading sight deterioration arrived. I'm not one for bi or varifocals so the glasses are regularly seen perched on my head when close up viewing is required.

Occasionally I have left the glasses on while observing however as I do not suffer with astigmatism, more often than not they're on my head, and often on the floor because I forget they're there while observing! (I really should buy string 🙄)

Despite not wearing the glasses most of the time at the eyepiece, I still tend to use long eye relief eyepieces. Current well used favourites in the budget to mid range being the OVL Nirvana ES and Altair Lightwave LER Planetary. My premium wide fov ep is the Altair 24mm UFF for that 'space port hole' experience. All suitable for specs wearers.

 

[Wikiastro]

I have a string for my glasses that I keep with my eyepieces.  It looks ridiculous, but as astronomy happens in the dark, what do I care!

[Carbon Brush]

For distance correction - near or far - the scope focus will handle the correction.
You can buy whatever eyepieces you like.
If you share the scope, a second viewer needs to tweak the focus.

For astigmatism correction, the scope won't handle it.
Whether you need to consider this depends on your prescription. Refer to the chart posted by @globular
If it is significant you need to correct for it.
This gives you 3 options.

1/ Wear specs, which means choosing eyepieces with long eye relief. But anyone can use the scope without re-focussing.
2/ Wear contact lenses - my preferred solution having significant astigmatism. Anyone can use the scope without refocussing.
3/ Buy Televue dioptrix eyepieces (or similar) and the astig correction rings. £££ spent. You can't easily share the scope.

HTH, David.

[globular]

29 minutes ago, ScouseSpaceCadet said:

My premium wide fov ep is the Altair 24mm UFF

@ScouseSpaceCadet I've been mulling over this EP.  But the reported 29mm eye relief puts me off somewhat.  Sounds great for glasses... but what about without glasses? Do you end up hovering above the EP... even with the rubber in the up position?

[Stuu]

Thanks for the input everyone. I don't have to share the scope with anyone usually so I'll just keep using the string on my specs as I also suffer from forgetting they're on my head. Tried contact lenses once, never again 😂

[ScouseSpaceCadet]

35 minutes ago, globular said:

@ScouseSpaceCadet I've been mulling over this EP.  But the reported 29mm eye relief puts me off somewhat.  Sounds great for glasses... but what about without glasses? Do you end up hovering above the EP... even with the rubber in the up position?

I squash my face against the eye cup just fine. 😀 JeremyS picked up the 'original' APM version and posted about it. They're nice eps.

 

Edited September 2, 2021 by ScouseSpaceCadet

[Louis D]

41 minutes ago, globular said:

@ScouseSpaceCadet I've been mulling over this EP.  But the reported 29mm eye relief puts me off somewhat.  Sounds great for glasses... but what about without glasses? Do you end up hovering above the EP... even with the rubber in the up position?

That's the design eye relief.  The eye lens is recessed so much that it ends up having 17mm of usable eye relief.  You will need to touch the folded down eye cup to see the field of view while wearing eyeglasses.

Edited September 2, 2021 by Louis D

[Louis D]

3 hours ago, Stuu said:

I currently have a fairly mild prescription for varifocals and get on fine without them when using my telescope.

I would never use an expensive pair of varifocals at the eyepiece.  There's too high of a risk of them being damaged.  That, and they probably have lots of microscratches that cause fine stars to twinkle as your head moves through the exit pupil.

I bought a pair of distance only eyeglasses with the lowest dispersion lens I could get so my astigmatism is corrected for use at the eyepiece.  I bought them through EyeBuyDirect for about $20.  They stay in a case in my astro toolbox and only get used for astronomy, so they don't build up daily microscratches.  When I need to read something up close, I simply look under my eyeglasses because my old eyes are fixed focus at 8 inches.

[globular]

49 minutes ago, Louis D said:

That's the design eye relief.  The eye lens is recessed so much that it ends up having 17mm of usable eye relief.  You will need to touch the folded down eye cup to see the field of view while wearing eyeglasses.

Thanks @Louis D.
It looked from the design that is was very recessed so I hoped someone would say that. 
I know the 30mm works ok both with and without glasses with it's reported 22mm eye relief.  I guess the 24mm is recessed about an additional 7 to 10mm or so... so they're similar in use.

[Gfamily]

There are astigmatism correctors that can be fitted to eyepieces if you'd rather take your spectacles off.

e.g. TeleVue Dioptrx - not cheap though.

[Louis D]

2 hours ago, Gfamily said:

There are astigmatism correctors that can be fitted to eyepieces if you'd rather take your spectacles off.

e.g. TeleVue Dioptrx - not cheap though.

Nor do they attach to all eyepieces.  There are various hacks out there (check CN in particular) to use them with certain Pentax, ES, and APM eyepieces.

[Louis D]

3 hours ago, globular said:

I know the 30mm works ok both with and without glasses with it's reported 22mm eye relief.  I guess the 24mm is recessed about an additional 7 to 10mm or so... so they're similar in use.

I measured 16mm of usable eye relief for the 30mm APM UFF, although it feels more like 17mm in use.  Both work comfortably with eyeglasses.  I think that's why the 24mm's eye lens was recessed so much, so it would have a similar feel to the 30mm and many other eyepieces with about 17mm of usable eye relief.  Too much eye relief can be a bad thing even with eyeglasses.

[globular]

1 minute ago, Louis D said:

I measured 16mm of usable eye relief for the 30mm APM UFF, although it feels more like 17mm in use.  Both work comfortably with eyeglasses.  I think that's why the 24mm's eye lens was recessed so much, so it would have a similar feel to the 30mm and many other eyepieces with about 17mm of usable eye relief.  Too much eye relief can be a bad thing even with eyeglasses.

Indeed.  If only manufacturers would publish 'usable' ER figures it would be much easier for everyone.

[Zermelo]

8 hours ago, globular said:

 

 

I've seen this chart on their website: https://www.televue.com/engine/TV3b_page.asp?id=54&Tab=_Choose and it seemed about right from my experience. My better eye has a prescription CYL of 0.5, which maps to 4mm.  I don't notice anything at 3.6mm, a little at 5.2mm, and my longest EP gives me 6mm, when it's very obvious.

But other sites quote "Buchroeder's rule", for which the maximum exit pupil for unaffected viewing is given by 1/SQRT(D), where D is the CYL value. This would suggest that exit pupils much above 1.4mm would show aberrations, which is not my experience. In fact, the minimum (non-zero) CYL value recorded in eye examinations is 0.25, which would still correspond to an exit pupil of 2mm. That seems very harsh.  

Have I got that right? The Televue graph above has a non-linear, decreasing horizontal scale so as to render the line as straight; otherwise it would be like this:

with the marked points following (almost) the plotted curve, corresponding to a relationship  EP = 2/D, quite different from the Buchroeder rule.

Has anyone else compared their prescription with the range of exit pupils they find acceptable?

 

 

 

[clarkpm4242]

@Stuu  I strongly recommend *NOT* using varifocals at the eyepiece.  The changing 'power' with head/eye position is a real pain.

As others have noted.  A pair of sIngle vision spectacles for astro use is the way to go.

Cheers, Paul.

[Second Time Around]

Although I started off observing with glasses, I'm now totally converted to using a Dioptrx.  In fact, so much so that I won't buy an eyepiece with an exit pupil of over 2mm that isn't Dioptrx compatible.  This is where my astigmatism becomes noticeable.  

Many Televue eyepieces accept a Dioptrx.  However, any of those that need an adapter will be unlikely to show the full field of view due to lack of eye relief.

Additionally, many other eyepieces can also be used with a Dioptrx (do a search here on Stargazer's Lounge for others not mentioned in this thread).  Note that with some you get a better fit if you add an O ring or elastic band in the groove below the top of the eyepiece or alternatively on the very lip.

There are 2 advantages of the Dioptrx that I particularly appreciate.  The first is that the quality, especially the coatings, are better than even my expensive glasses.  The second is that my astigmatism angle varies between my annual eye tests.  With the Dioptrx I can dial in the precise angle required at any time.

Tests I did myself showed that I need 0.25 dioptres extra astigmatism correction at night.  I also need an extra 0.50 correction at night for my short-sightedness (this is called night myopia).

[W0nderste]

11 hours ago, Second Time Around said:

Although I started off observing with glasses, I'm now totally converted to using a Dioptrx.  In fact, so much so that I won't buy an eyepiece with an exit pupil of over 2mm that isn't Dioptrx compatible.  This is where my astigmatism becomes noticeable.  

Many Televue eyepieces accept a Dioptrx.  However, any of those that need an adapter will be unlikely to show the full field of view due to lack of eye relief.

Additionally, many other eyepieces can also be used with a Dioptrx (do a search here on Stargazer's Lounge for others not mentioned in this thread).  Note that with some you get a better fit if you add an O ring or elastic band in the groove below the top of the eyepiece or alternatively on the very lip.

There are 2 advantages of the Dioptrx that I particularly appreciate.  The first is that the quality, especially the coatings, are better than even my expensive glasses.  The second is that my astigmatism angle varies between my annual eye tests.  With the Dioptrx I can dial in the precise angle required at any time.

Tests I did myself showed that I need 0.25 dioptres extra astigmatism correction at night.  I also need an extra 0.50 correction at night for my short-sightedness (this is called night myopia).

Great info thanks.

what eyepieces are you using with the dioptrx if you don't mind me asking?

 

 

[Second Time Around]

Currently the 8-24mm Baader zoom,  the Svbony 7-21mm zoom, a 28mm/68 deg Explore Scientific and a 22mm Vixen LVW.

In the past I've used a 22mm Nagler, a 22mm/70 Deg Omegon Redline and a 20mm Pentax XW.