TeleVue Dioptrx

[Naemeth]

Does anyone know if these can be used with other eyepieces, or does it very much depend on the eyepiece design as to whether they can be used or not?

[alan potts]

I don't know for sure but when you think they are to be used on TVs from 55mm Plossl right down to a 2.5mm Nagler I would be shocked if they didn't. Are they to correct astigmatism, I am sure they must be as long or short sightedness is taken up by the scope focusing system, I have to refocus just a tiny bit from one eye to the other. So I would have thought they are the same as having glasses on but you haven't. What I cant see is how they connect to the eyepiece all of my TV's have rubber tops, unless you remove them.

Alan.

[Naemeth]

I don't know for sure but when you think they are to be used on TVs from 55mm Plossl right down to a 2.5mm Nagler I would be shocked if they didn't. Are they to correct astigmatism, I am sure they must be as long or short sightedness is taken up by the scoepe focusing system, I have to refocus just a tiny bit from one eye to the other. So I would have thought they are the same as having glasses on but you haven't. What I cant see is how they connect to the eyepiece all of my TV's have rubber tops, unless you remove them.

Alan.

They correct astigmatism, I'm thinking they might be a cheaper alternative to contacts, especially if I'll be able to use fairly short eye relief eyepieces with the corrector there.

[cantab]

Looking on the Televue website I think you do remove the eyeguard, push the Dioptrix connector on, then push the eyeguard back onto the Dioptrix. So I suppose they would work with eyepieces that happen to use the same eyeguard attachment as Televue EPs do.

[Astrobits]

Short eye relief eyepieces are usually short f/l and hence give a small exit pupil. It might be that you don't need astigmatic correction when using just the very centre of your eye. Try without before purchasing. As a test put a pinhole between your eye and the eyepiece to further reduce the area of your eye in use and see if there is any deterioration when removing the pinhole. Jupiter should be a reasonable subject for this experiment.

Of course, on the longer f/l eyepieces you will need astigmatic correction but there you might get away with normal specs if the eye relief is large enough. You could try the pinhole test on all your eyepieces to determine which ones need the corrector and which can be used with just your specs or nothing at all.

Nigel

[Naemeth]

Thanks for that Nigel, I'll give it a try. Just out of interest, roughly at what exit pupil does astigmatism become apparent?

[username]

roughly at what exit pupil does astigmatism become apparent?

It will depend on the severity of your astigmatism. An astigmatism that need more correction will become apparent at a smaller exit pupil. When the exit pupil is small enough so that the surface of your eye lens is locally distortion free you won't notice the astigmatism. That's the way I understand it. You'd have to look into what the numbers on your perscription mean in term of degree of distortion of the native eye surface.

[username]

It will depend on the severity of your astigmatism. An astigmatism that need more correction will become apparent at a smaller exit pupil. When the exit pupil is small enough so that the surface of your eye lens is locally distortion free you won't notice the astigmatism. That's the way I understand it. You'd have to look into what the numbers on your perscription mean in term of degree of distortion of the native eye surface.

or just try out different eyepieces. If you have a barlow that unscrews you can get 2x and ~1.5-1.6x changes. Might be enough of a range from that to test

[cantab]

Just out of interest, roughly at what exit pupil does astigmatism become apparent?

According to Tele Vue: http://www.televue.com/engine/TV3b_page.asp?id=54&Tab=_Choose

[Naemeth]

It will depend on the severity of your astigmatism. An astigmatism that need more correction will become apparent at a smaller exit pupil. When the exit pupil is small enough so that the surface of your eye lens is locally distortion free you won't notice the astigmatism. That's the way I understand it. You'd have to look into what the numbers on your perscription mean in term of degree of distortion of the native eye surface.

-0.75 for my observing eye. I suppose it's really a "see how it goes" thing.

According to the TV chart, I should be able to use anything from 3mm exit pupil, or less than 15mm in my current scope . This may make things a lot cheaper in the short and long run .

[username]

-0.75 for my observing eye. I suppose it's really a "see how it goes" thing.

I have -0.5 astigmatism plus short sightedness in my left, near perfect in my right no astigmatism. I don't bother with glasses when I observe. It's weird, I seem to pick out better colour on Jupiter with my left and I'm right eye dominant too although I find that I can get eye strain if I use my left for too long.

I don't find the left eye can't get in focus though however the largest exit pupil of my scope is ~2mm so according to the graph cantab linked too it's no surprise it doesn't bother me but just try out different combos, especially before spending money! Everyones tolerance to it will be a bit different

[Naemeth]

I have -0.5 astigmatism plus short sightedness in my left, near perfect in my right no astigmatism. I don't bother with glasses when I observe. It's weird, I seem to pick out better colour on Jupiter with my left and I'm right eye dominant too although I find that I can get eye strain if I use my left for too long.

I don't find the left eye can't get in focus though however the largest exit pupil of my scope is ~2mm so according to the graph cantab linked too it's no surprise it doesn't bother me but just try out different combos, especially before spending money! Everyones tolerance to it will be a bit different

That's good then, I guess I'm just so used to wearing glasses, because I've been wearing them since I was 18 months old. I will see about trying shorter FL eyepiece later on, and I may try again with my SW MA to see if I can use it without astigmatism being there.

[jabberwocky]

I was eavesdropping David nagler demonstrating the dioptrix to someone at kelling Heath last year and the question was asked and the response was yes they do, maybe not all eyepieces though.

[Naemeth]

Turns out, as I was observing yesterday, I found that my astigmatism didn't bother me much, if at all with my 10mm MA, I even kept my glasses off for most of the rest of my observing session. I seem to get better contrast, and this is probably because my glasses have a lot of radial scratches on (haven't taken very good care of them , but they are 3 years old), so I may be getting a few Orthoscopics at some point.

Thanks for the help everyone!

[username]

Good news! Glad you managed to test without glasses, I'm a relative newcomer to having to wear them so it wasn't too weird for me to try observing without them.

How long did you test for? Like I said above sometimes after using my astigmatic eye for a long time at the eyepiece I can get a bit of eye strain sometimes, a weird pain at the back of the eyeball. Takes well over an hour for it to develop though for me. Just something to consider before you start investing in shorter orthos, although they come up pretty cheap on ABS and you should be able to resell them for the same value.

[E621Keith]

Does anyone know if these can be used with other eyepieces, or does it very much depend on the eyepiece design as to whether they can be used or not?

Yes, the dioptrx locks onto the eyepiece using a twist lock compression ring and will fit other eyepieces with eye cup external diameter of approximately 44mm. I tried with Meade S5K UWA and LVW.

[Naemeth]

Good news! Glad you managed to test without glasses, I'm a relative newcomer to having to wear them so it wasn't too weird for me to try observing without them.

How long did you test for? Like I said above sometimes after using my astigmatic eye for a long time at the eyepiece I can get a bit of eye strain sometimes, a weird pain at the back of the eyeball. Takes well over an hour for it to develop though for me. Just something to consider before you start investing in shorter orthos, although they come up pretty cheap on ABS and you should be able to resell them for the same value.

About 30 minutes I was testing them for I think . I've had them off for an hour before and been fine.

Thanks for the info Keith .