18 replies to this topic

[amooney]

Apologies if this has been discussed elsewhere, but is there anything that can be done to counteract astigmatism while observing through eyepieces? I would love to be able to observe without having to wear glasses, especially through my 2-inch eyepieces. The view is so much more immersive being able to get in closer to the lens. I think Televue made something like an adjustable diopter, but I'm not exactly sure about that. 

[ButterFly]

More astigmatism!!!  But in the opposite direction.  Dioptrx lets you do that.

[RTLR 12]

Here is the TeleVue site...

 

https://www.televue...._page.asp?id=54

[amooney]

Does the Televue Dioptrx work with other eyepiece brands or just Televue? I use mostly Explore Scientific eyepieces, plus a 52mm custom.

Edited by amooney, 09 September 2024 - 05:05 PM.

[RTLR 12]

They are made to fit Televue eyepieces, but they can be used on other eyepieces with some creative adaptations.

Stan

[Notdarkenough]

Try this thread: https://www.cloudyni...ible-eyepieces/

[vsteblina]

contacts...

[ButterFly]

contacts...

Yes and no - one has to be careful with that.  Contacts have a fixed sized window of correction.  If your pupil is larger than that, it's just junk getting through.  The 5mm window of the contacts I chose were not sufficient for me.  Talking with my doctor, it became clear that noting short of the whole eye style contacts work well for my pupil size.

 

But, any prescription comes from a particular set of measurement, under particular lighting conditions.  If those lighting conditions, which affect pupil size, don't match that when you'll observe, you can get less than great correction from the edges that weren't ever measured.  For large exit pupils, I had my doctor dilate and correct the astigmatism there.  They do much better than my "ordinary" glasses for naked eye and wide eyed pupil viewing.  A focuser can correct for those spherical errors that may emerge with wide eyed pupils, but they can't correct any difference in cylindrical correction that may emerge from wide eyed viewing.

 

I prefer to keep my glasses on when viewing.  Cougars won't be waiting for me to get my glasses on, so I won't either!  Although Dioptrx has the potential to fully correct absolutely ever last bit of astigmatism, when two are stacked, the effect is a reduction in apparent field from being that much farther away.  I just bring along my 13 Ethos when glasses shopping and make sure I can see the field stop with them.  I can always get a separate pair, if my fashion sense develops to point of desiring fashion goggles.  It hasn't yet, and I don't expect it to.

[fishhuntmike]

Dioptrx work for my minute amount of astigmatism. I only use it on my 31 Nagler but removing its eyecups (without dioptrx) allows me to use two of my 5 pair of glasses and still see the full field. The 22 nagler works too. Choice of glasses make a big difference. Aviators are bad. Dioptrx sadly cut into my AFOV with my 21 ethos so I dont use it anymore. I substitute a 17mm ES 92 which is a favorite "superwide" eyepiece. A small enough exit pupil using shorter focal length eyepieces helps some depending on the level of astigmatism and there are lots of threads and charts for this. Disappointing huh. Bifocals are lousy too for widefield eyepieces with large eye relief. Small sized low profile single-prescription glasses work for me and it helps not having big cheeks or deeply sunk eyes.

Edited by fishhuntmike, 09 September 2024 - 09:07 PM.

[Captain Quark]

A small enough exit pupil that your astigmatism has no effect. My limit is 2mm exit pupil. There’s a chart on the TV site on the Dioptrx page I think. Won’t help for your 2” inch eye pieces.

Edited by Captain Quark, 10 September 2024 - 11:29 AM.

[Bill Weir]

Does the Televue Dioptrx work with other eyepiece brands or just Televue? I use mostly Explore Scientific eyepieces, plus a 52mm custom.

The only ES eyepiece I own is the 100° 20mm. My Dioptrix fits perfectly on it. That being said because that eyepiece has a recessed concave eye lens the height the Dioptrix adds makes it difficult/impossible to see the entire FOV. Really though on the whole the 20 is my finder eyepiece so the Dioptrix mostly lives on my 10mm Ethos. 

 

Bill

[vsteblina]

Yes and no - one has to be careful with that.  Contacts have a fixed sized window of correction.  If your pupil is larger than that, it's just junk getting through.  The 5mm window of the contacts I chose were not sufficient for me.  Talking with my doctor, it became clear that noting short of the whole eye style contacts work well for my pupil size.

 

But, any prescription comes from a particular set of measurement, under particular lighting conditions.  If those lighting conditions, which affect pupil size, don't match that when you'll observe, you can get less than great correction from the edges that weren't ever measured.  For large exit pupils, I had my doctor dilate and correct the astigmatism there.  They do much better than my "ordinary" glasses for naked eye and wide eyed pupil viewing.  A focuser can correct for those spherical errors that may emerge with wide eyed pupils, but they can't correct any difference in cylindrical correction that may emerge from wide eyed viewing.

 

 

Gee, and I thought I was a pain in the butt for asking to sit in complete darkness for 20 minutes and then do the eye exam in the dark!!!!

 

You bring up good points.  I spent a lot of time looking for a good ophthalmologist and then gave him a copy of the Sky and Telescope article on the eye as an observing tool.  That really helped.

 

Every year he gives me a five pack of trial contact lenses with a +1 diaptor corrector for naked eye viewing.  That really helps in a dark sky site for naked eye observing.
 

[sevenofnine]

So, whole eye contacts with the correction done with eyes dilated is the trick? The correction is for distance right? 

[ButterFly]

Gee, and I thought I was a pain in the butt for asking to sit in complete darkness for 20 minutes and then do the eye exam in the dark!!!!

 

You bring up good points.  I spent a lot of time looking for a good ophthalmologist and then gave him a copy of the Sky and Telescope article on the eye as an observing tool.  That really helped.

 

Every year he gives me a five pack of trial contact lenses with a +1 diaptor corrector for naked eye viewing.  That really helps in a dark sky site for naked eye observing.
 

It's great that you found a good doctor.  It's not much different than us needing prosthetics for pole vaulting!

[rjacks]

Lasik surgery. You only need to do one eye!

[timelapser]

If you have an old pair of glasses with your current astigmatism correction you could try cut out a circular disc centred on the optical axis, and then work out a way to mount it in your eyepiece.

[davidgmd]

Gee, and I thought I was a pain in the butt for asking to sit in complete darkness for 20 minutes and then do the eye exam in the dark!!!!

 

You bring up good points.  I spent a lot of time looking for a good ophthalmologist and then gave him a copy of the Sky and Telescope article on the eye as an observing tool.  That really helped.

 

Every year he gives me a five pack of trial contact lenses with a +1 diaptor corrector for naked eye viewing.  That really helps in a dark sky site for naked eye observing.
 

  
What issue of S&T is that? I’ve never heard of it taking 20 minutes to achieve full scotopic pupil dilation.

[TayM57]

If you want the truly immersive experience, contacts are the way to go.

 

However, the stronger the astigmatism, the more uncomfortable the contacts can be, depending on the type. It's very difficult to find contacts that work for you as your astigmatism diopter approaches 4.00, like mine is.

 

I'm going to give contacts one more try after my next eye exam at a different eye doctor... after sitting in the dark for 30 minutes or so. That'll be my last hurrah to try to go back to Ethos.

[Chris K]

I have astigmatism (1.5) and Dioptrx are terrific. I do have to fiddle a bit between focus and rotation of the Dioptrix but I can turn a 'seagull' into a dot.