astigmatism correction solution for eyepieces

[OzEclipse (Joe Cali)]

On another message in this forum, this message was posted : -

Originally Posted by rrussell1962

I use the ES 14mm 82 degree in an 18" F4.5 and like it a lot. Eye relief can be a bit tight, but because of astigmatism in both eyes I am stuck with either glasses with good views and eye relief issues, or contacts with better eye relief but worse vision and drying eyes during the night! If you do not have that issue you may find the ES a good choice and excellent value.

I have found a probable solution to this age old problem.

I had my eye test 3 weeks ago. I asked the optometrist about whether I could order a circular lens of a specified diameter with anti reflection coatings and just the astigmatism script in the lens. He confirmed that I could do that but that the lens cutting machine needs a profile to follow to cut the lens outline. I can't just specify a diameter. So he said that if I give them the holder I am going to use to mount the lens with the recess, they can cut the lens or lenses to match. My astigmatism is the result of an eye accident 20 years ago and the astigmatism part of the script doesn't seem to change over long periods of time So I am thinking that this might be a worthwhile exercise. If yours changes regularly then this is going to cost a bit more to replace the lens each couple of years. Would also suggest that you'll need one per eyepiece. If you observe alone, the approach will be different to than if you observe with people with good eyes.

So the next step is to measure up all my eyepieces and design some correction lens holders that fit over the eyepieces. I think I'll try to standardize the lens recess to one or two sizes so I can just send in one holder but have several lenses made. At first I was going to ask them to mark the edge to orient the lens but then realized that it's easy and quick to rotate the whole eyepiece until the image becomes sharp.

Joe

[MortonH]

Sounds like a DIY Dioptrx. Cool if it works.

[Wavytone]

Yup its a DIY Dioptrix.

[dimithri86 (Dimithri)]

Hi Joe,

Are you able to PM me the approximate cost for this?

My wife is a optometrist and I have access to her lab. I want to see if this works for me. I have quite bad astigmatism for normal vision, but it seems Ok for astronomy. But I want to determine if I can see more with correction.

If this works, I also want to offer this service to others at a low cost.

[pixelsaurus (Mike)]

This method seemed to be quite common in the US in the 70's and 80's. I think there is some mention of this in Sky & Telescope "Gleanings" from that period.

[OzEclipse (Joe Cali)]

There seems to be some misunderstanding of my post.

I wasn't trying to claim that it's a new idea and I haven't applied for a patent. Yes TV make the correctors for their eyepieces. But these are made to fit the rubber eyeguard groove after the eyeguard is removed. Not everybody with astigmatism has a set of TV eyepieces or wants to go out and buy them. The TV dioptrix might serendipitously fit the rubber eyeguard of some other brands but no guide to this is available.

I see posts from time to time mentioning problems with astigmatism, eyepieces with insufficient eye relief for glasses for astigmatism sufferers etc.

So I was just letting astigmatism sufferers with non-TV eyepieces know that there is a way to make a corrector for any eyepiece via your regular optometrist. The lens profiling machines shape the OD of the lens by tracing the frames or any other template or for an eyepiece, by tracing a lens mounting you provide.

If you go down this path, do spend the extra $ on anti reflection coatings for the lenses.

Cheers

Joe

[Renato1 (Renato)]

Hi Joe,
Eyeglass scrips don't change much, so when I'd get a new set of eyeglasses I'd ask the people at the shop if they could cut the old eyeglass lenses down to circles, and put a notch on top for the right eye and two notches for the left eye. This they did. Then I stuck the lenses onto eyepieces or into binoculars with Blutack.

But I only had 1.25" eyepieces back then, and I only stuck and left the lenses on my 40mm eyepiece, and into my 10x70 binoculars - where they still are. My astigmatism isn't so bad at a 3mm or less exit pupil, so that when I tried sticking the eyeglass lenses to 32mm and 26mm eyepieces, while they worked, it seemed more effort than what it was worth having to constantly rotate the position of the eyepiece in my C8's diagonal as I moved around the sky.

I did discover another method to get rid of astigmatism in my 14.5" dob. Instead of going down to a 6 or 7mm exit pupil which gave me a view with very bad astigmatism, I went down to a 9mm exit pupil instead. Thus I could easily twist my eye to a position where the astigmatism disappeared, without blanking out part of the image (as would have been the case with the 6 or 7mm exit pupils).

You are dead right about the need for multicoatings as far as I am concerned, though some people don't seem to notice the internal reflections on uncoated eyeglass lenses - which I find strange as they drive me batty.
Regards,
Renato