44 replies to this topic

[Rustler46]

To add to Don's very useful pros and cons I use glasses on the rare occasions I view with others.  On my own I prefer a Dioptrx for the following reasons:

 

 

1) I wear my glasses on a cord and have no problems taking them on and off - it becomes automatic

 

2) In any event, I have no presbyopia and so don't need glasses at all for looking at close range objects such as screens or maps

 

3) I have a Dioptrx on my finder eyepiece, but even without this I don't find astigmatism critical on a finder as it's doing just that - finding

 

4) The coatings are better than on even the top of the range Rodenstock lenses on my glasses

 

5) The angle of my astigmatism changes between my annual eye tests.  With a Dioptrx I can adjust this at the telescope

 

6) I find that, like many, I need an extra 0.25 correction for astigmatism at night

 

7) And most of all, having done head to head tests I found that I can see more with a Dioptrx than with my glasses

A year ago my eye test showed 1/2 diopter astigmatism. The Dipotrx corrected well for that with large exit pupils. Then as time went by it seems like it wasn't enough correction. This year's eye test shows my astigmatism has remained at1/2 diopter. So your comment #6 seems to apply in my case. Any idea what causes that effect?

 

Russ

[Michael Covington]

The size of the pupil.

[Starman1]

Michael is right--as your pupil expands at night, and it is always larger in complete darkness than it is in a dim optometrist's room,

astigmatism increases.  You've had your pupils dilated and noticed the horrible astigmatism that generates--flares and spikes on every light--

and a curved cornea only gets worse the wider the pupil's view of it.

 

An extra 1/4 to 1/2 diopter at night is not uncommon.

You can check it out by looking at the stars at night with your glasses on.  If they are not tiny little pinpoints, but still have a distorted shape or flares or spikes,

then your astigmatism correction is insufficient for nighttime use.  It's a revelation when you see stars as tiny little pinpoints with the naked eye + glasses.

It made me realize that I had needed nighttime astigmatism correction all my life.

 

One other thing--the extra astigmatism correction you need at night is likely to be a small enough extra that your daytime correction can likely

just be adjusted to that nighttime correction without causing problems during the day.  Ask your optometrist or ophthalmologist about that.

I discovered my daytime astigmatism was 0.75 diopter and nighttime 1.0 diopter and I just changed my glasses to 1.0 without any negative aspects for day use.

It's so nice to see stars at night as tiny points.  And really bright ones have a diffraction ring!

[Rustler46]

Michael is right--as your pupil expands at night, and it is always larger in complete darkness than it is in a dim optometrist's room,

astigmatism increases.  You've had your pupils dilated and noticed the horrible astigmatism that generates--flares and spikes on every light--

and a curved cornea only gets worse the wider the pupil's view of it.

 

An extra 1/4 to 1/2 diopter at night is not uncommon.

You can check it out by looking at the stars at night with your glasses on.  If they are not tiny little pinpoints, but still have a distorted shape or flares or spikes,

then your astigmatism correction is insufficient for nighttime use.  It's a revelation when you see stars as tiny little pinpoints with the naked eye + glasses.

It made me realize that I had needed nighttime astigmatism correction all my life.

 

One other thing--the extra astigmatism correction you need at night is likely to be a small enough extra that your daytime correction can likely

just be adjusted to that nighttime correction without causing problems during the day.  Ask your optometrist or ophthalmologist about that.

I discovered my daytime astigmatism was 0.75 diopter and nighttime 1.0 diopter and I just changed my glasses to 1.0 without any negative aspects for day use.

It's so nice to see stars at night as tiny points.  And really bright ones have a diffraction ring!

Thanks for the clarification, Don. I might just put my 1/2 diopter Dioptrx up for sale to partially fund one of stronger correction. My glasses don't have any built-in astigmatism correction, since it is so slight. They are progressives that are not very useable at the telescope anyway. My major defect is 3.5 to 5.0 diopter (right/left eye) near-sightedness. But that is easily handled by eyepiece focus. 

 

My decades long training of the right eye is now being supplanted by a similar journey with the left. The slight cataracts in the right eye makes that one significantly dimmer than the left eye. Life's changes are interesting.

 

Best Regards,

Russ

[Starman1]

Russ, cataract formation can mimic the effects of astigmatism by flaring stars.

But if your daytime prescription has no astigmatism correction, the 1/2 diopter correction at night should correct noticeably better.

As to whether you would need 1/2 diopter more (=1.0) would be hard to determine.  There is no longer a 0.75 diopter DioptRx.

Single vision glasses for night use might be the way to go--they are pretty cheap on-line and you go get a second pair for less

and get one pair with 0.75 correction and another with 1.0 correction and correct the near-sightedness at the same time.

One pair would give you sharper stars.  That would be the correction to keep.

If it's 1.0 diopter, then keep the glasses hanging around the neck for use with a finder, or naked eye views and get a DioptRx for the scope.

 

One thing of note, however, and that is that nearly all myopes get better correction with a half diopter stronger spherical correction at night (more minus).

I think it would be a revelation for you to see the night sky in perfect pinpoint focus and see the images in the eyepiece the same, wearing the same glasses.

And these days, there are a slew of good eyepieces that are glasses friendly.

 

Most of the time, guys that have gotten older also have accompanying presbyopia on top of everything else.

That might mean you can't read notes, DSC, Paracorr setting, etc.

Two solutions: bifocals, or a small magnifying glass.  Since even single vision glasses would correct the astigmatism, a low power magnifying glass could be kept near the notes.

I got a 4" lens 2.5x magnifier with light and it beats a simple red light hands down at my notes and atlas table.

 

However, assuming you don't want to use glasses at the scope, you could simply try reading notes at night with the DioptRx held between eye and notes to see if you can easily read the notes.

You'll have to be close, due to the myopia, but if the 0.5 diopter isn't strong enough to correct astigmatism, you'd know right away.

Edited by Starman1, 10 August 2022 - 06:06 PM.

[Rustler46]

Russ, cataract formation can mimic the effects of astigmatism by flaring stars.

But if your daytime prescription has no astigmatism correction, the 1/2 diopter correction at night should correct noticeably better.

As to whether you would need 1/2 diopter more (=1.0) would be hard to determine.  There is no longer a 0.75 diopter DioptRx.

Single vision glasses for night use might be the way to go--they are pretty cheap on-line and you go get a second pair for less

and get one pair with 0.75 correction and another with 1.0 correction and correct the near-sightedness at the same time.

One pair would give you sharper stars.  That would be the correction to keep.

If it's 1.0 diopter, then keep the glasses hanging around the neck for use with a finder, or naked eye views and get a DioptRx for the scope.

 

One thing of note, however, and that is that nearly all myopes get better correction with a half diopter stronger spherical correction at night (more minus).

I think it would be a revelation for you to see the night sky in perfect pinpoint focus and see the images in the eyepiece the same, wearing the same glasses.

And these days, there are a slew of good eyepieces that are glasses friendly.

 

Most of the time, guys that have gotten older also have accompanying presbyopia on top of everything else.

That might mean you can't read notes, DSC, Paracorr setting, etc.

Two solutions: bifocals, or a small magnifying glass.  Since even single vision glasses would correct the astigmatism, a low power magnifying glass could be kept near the notes.

I got a 4" lens 2.5x magnifier with light and it beats a simple red light hands down at my notes and atlas table.

 

However, assuming you don't want to use glasses at the scope, you could simply try reading notes at night with the DioptRx held between eye and notes to see if you can easily read the notes.

You'll have to be close, due to the myopia, but if the 0.5 diopter isn't strong enough to correct astigmatism, you'd know right away.

Lots of good information to chew on, Don. Thanks for that. Do you have any thoughts on the effects of using contact lenses. I use the soft type for daytime driving. That works with my wrap-around sunglasses. But there's no correction for astigmatism. My progressive glasses have none either. It's amazing how the brain can make the extremely warped progressive's view look quite normal. My wife couldn't handle the progressive view. It made her ill. For me there's no issue.

 

But I haven't liked the contacts for use at the telescope. Seems like to two extra surfaces (air/plastic & plastic/tears/eyeball) didn't help the overall optical performance. Since my major eye defect is myopia (nearsightedness) that is easily handle by focusing. The astigmatism is only noticeable at large exit pupils.

 

Thanks for your help, Don.

 

Russ

[Michael Covington]

Cataract formation can also *cause* astigmatism, by distorting the shape of the lens.  That is, you might see flares either because the light is hitting the not-quite-transparent cataract, or because the lens is pushed into a shape that doesn't have circular symmetry.   Notoriously, astigmatism of this kind isn't completely correctable with glasses or lenses like the DioptRx because it doesn't have elliptical symmetry either.

[Michael Covington]

Progressive-lens eyeglasses normally *do* include prescribed correction for astigmatism.  Mine do.

[Chris K]

My astigmatism is 1.5.
Stars have a V-shape and the dioptrx does well to eliminate it.

[BGazing]

Russ, cataract formation can mimic the effects of astigmatism by flaring stars.

But if your daytime prescription has no astigmatism correction, the 1/2 diopter correction at night should correct noticeably better.

As to whether you would need 1/2 diopter more (=1.0) would be hard to determine.  There is no longer a 0.75 diopter DioptRx.

Single vision glasses for night use might be the way to go--they are pretty cheap on-line and you go get a second pair for less

and get one pair with 0.75 correction and another with 1.0 correction and correct the near-sightedness at the same time.

One pair would give you sharper stars.  That would be the correction to keep.

If it's 1.0 diopter, then keep the glasses hanging around the neck for use with a finder, or naked eye views and get a DioptRx for the scope.

 

One thing of note, however, and that is that nearly all myopes get better correction with a half diopter stronger spherical correction at night (more minus).

I think it would be a revelation for you to see the night sky in perfect pinpoint focus and see the images in the eyepiece the same, wearing the same glasses.

And these days, there are a slew of good eyepieces that are glasses friendly.

 

Most of the time, guys that have gotten older also have accompanying presbyopia on top of everything else.

That might mean you can't read notes, DSC, Paracorr setting, etc.

Two solutions: bifocals, or a small magnifying glass.  Since even single vision glasses would correct the astigmatism, a low power magnifying glass could be kept near the notes.

I got a 4" lens 2.5x magnifier with light and it beats a simple red light hands down at my notes and atlas table.

 

However, assuming you don't want to use glasses at the scope, you could simply try reading notes at night with the DioptRx held between eye and notes to see if you can easily read the notes.

You'll have to be close, due to the myopia, but if the 0.5 diopter isn't strong enough to correct astigmatism, you'd know right away.

I am currently at 0.5 cyl, and +0.75 and +1.00 for distance and +1.00 add for reading. I don't use bifocals. I guess it does not make any difference which of the two I use at the eyepiece? 

[Starman1]

I am currently at 0.5 cyl, and +0.75 and +1.00 for distance and +1.00 add for reading. I don't use bifocals. I guess it does not make any difference which of the two I use at the eyepiece?

If your cylinder (astig.) is only 0.5 diopters, a DioptRx of the same is likely to be fine. And if you use single vision glasses, they'd be fine for the scope and the sky, so you do have a choice.

If you see stars, naked eye, sharper with glasses on, I'd suggest using them at the eyepiece.

If you see stars, naked eye, about the same without glasses, then the DioptRx becomes a viable choice.

Either way, I'd suggest long eye relief eyepieces.

[BGazing]

If your cylinder (astig.) is only 0.5 diopters, a DioptRx of the same is likely to be fine. And if you use single vision glasses, they'd be fine for the scope and the sky, so you do have a choice.

If you see stars, naked eye, sharper with glasses on, I'd suggest using them at the eyepiece.

If you see stars, naked eye, about the same without glasses, then the DioptRx becomes a viable choice.

Either way, I'd suggest long eye relief eyepieces.

Stars are sharper with my distance glasses for sure. But my question is - given that the difference between my distance and reading glasses is just diopter - I can use both in the eyepice, and just adjust the focus? Reading glasses work better in the dark (more diopter) and are useful when reading charts and EP and P2 markings...

[TayM57]

Stars are sharper with my distance glasses for sure. But my question is - given that the difference between my distance and reading glasses is just diopter - I can use both in the eyepice, and just adjust the focus? Reading glasses work better in the dark (more diopter) and are useful when reading charts and EP and P2 markings...

It doesn't work like that. I did try, and the view was much worse with my reading glasses. I couldn't get close to the correction I can with my distance glasses which are corrected for infinity. 

[BGazing]

It doesn't work like that. I did try, and the view was much worse with my reading glasses. I couldn't get close to the correction I can with my distance glasses which are corrected for infinity. 

Thought so, thanks!

[davidgmd]

It doesn't work like that. I did try, and the view was much worse with my reading glasses. I couldn't get close to the correction I can with my distance glasses which are corrected for infinity. 

  
That seems odd to me, because it should work that way for the spherical component of the refractive error. The telescope focuser can correct for any residual hyperopic (+) or myopic (-) error at the eyepiece, whether wearing distance or reading glasses or no glasses at all. Unless your focuser runs out of in- or out-travel.  It’s only the astigmatic error that needs to be corrected with glasses or Dioptrx.

  
My view through the scope is just as good with my distance-only astronomy glasses as it is with my intermediate-only computer glasses. Both have the same astigmatism correction. The astronomy glasses are set for infinity. The computer glasses have +1.75 diopters of “add,” so they are set at about 22” (1/1.75 meter). The 2 pairs of glasses are obviously non-parfocal: I have to focus in or out if switching between them. But the views at focus are equally sharp.

[Michael Covington]

That's actually the computer glasses, not the astronomy glasses, that have +1.75 add, right? (Minor detail but you never know who will read this out of context.)

[davidgmd]

That's actually the computer glasses, not the astronomy glasses, that have +1.75 add, right? (Minor detail but you never know who will read this out of context.)

 
Yes, that’s what the post says.

[turtle86]

Cataract formation can also *cause* astigmatism, by distorting the shape of the lens.  That is, you might see flares either because the light is hitting the not-quite-transparent cataract, or because the lens is pushed into a shape that doesn't have circular symmetry.   Notoriously, astigmatism of this kind isn't completely correctable with glasses or lenses like the DioptRx because it doesn't have elliptical symmetry either.

 

I recently found out that I have mild astigmatism (.75), with mild cataracts as the likely culprit. I never noticed any objectionable astigmatism when observing but thought I'd try out a TeleVue Dioptrx, hoping that I might see a subtle yet noticeable improvement in the views. I saw no improvement at all, and was a little surprised by that, but your explanation makes a lot of sense.

[TayM57]

  
That seems odd to me, because it should work that way for the spherical component of the refractive error. The telescope focuser can correct for any residual hyperopic (+) or myopic (-) error at the eyepiece, whether wearing distance or reading glasses or no glasses at all. Unless your focuser runs out of in- or out-travel.  It’s only the astigmatic error that needs to be corrected with glasses or Dioptrx.

  
My view through the scope is just as good with my distance-only astronomy glasses as it is with my intermediate-only computer glasses. Both have the same astigmatism correction. The astronomy glasses are set for infinity. The computer glasses have +1.75 diopters of “add,” so they are set at about 22” (1/1.75 meter). The 2 pairs of glasses are obviously non-parfocal: I have to focus in or out if switching between them. But the views at focus are equally sharp.

This was some years back. I'll give it another try but I do remember my reading glasses essentially being unusable at the EP. I could not get pinpoint stars unless I switched to my distance glasses.

 

Will come back to this when I've had the chance try again. Possible, that the lens on my reading glasses aren't ground out properly. I do have to tilt them at a severe angle to even use them as reading glasses in the house, which is why I almost never use them.

 

 

[fishhuntmike]

Ive used a 1.25 dioptrx for years in my 31 nagler. I ordered a 1.5 a couple days ago so I will have a second to put on my Ethos 21mm to use without glasses but slightly constricted field of view with the dioptrx. Havent used the 21 ethos much in years since astigmatism crept my way.