Astigmatic eyes - what to do ?

My eyes suffer a moderate amount of astigmatism which is only really a
problem when using a telescope. I can never focus stars to anything
like a sharp point once the exit pupil gets bigger than say 3mm.

Whats the best solution?

I already have spectacles which I normally only use when driving the
car at night.
I would prefer to not use them as I observe from my light poluted back
yard and reflections off them are a bother.

Contact lenses maybe ?

"Geoff" wrote in message
...

My eyes suffer a moderate amount of astigmatism which is only really a
problem when using a telescope. I can never focus stars to anything
like a sharp point once the exit pupil gets bigger than say 3mm.

Whats the best solution?

I already have spectacles which I normally only use when driving the
car at night.
I would prefer to not use them as I observe from my light poluted back
yard and reflections off them are a bother.

Contact lenses maybe ?

My understanding is that contact lenses do not correct astigmatism very
well. I wear glasses (high quality, anti-reflection coated; Zeiss "Lantal"
lenses are the best I've found). And I use eyepieces with long eye relief
(Tele Vue Radian).

You can get an eyeglass maker to make lens elements that you can somehow
attach to your eyepieces to correct astigmatism. You will then have to get
the eyepiece oriented just right in order to use it.

--
Clear skies,

Michael Covington -- www.covingtoninnovations.com
Author, Astrophotography for the Amateur
and (new) How to Use a Computerized Telescope

On Sat, 11 Oct 2003 22:54:39 -0400, "Michael A. Covington"
wrote:

My understanding is that contact lenses do not correct astigmatism very
well.

Hard contacts will do an excellent job of correcting astigmatism, although they
are more expensive and less comfortable for many than soft lenses.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On 10/11/03 10:54 PM, in article ,
"Michael A. Covington"
wrote:


"Geoff" wrote in message
...

My eyes suffer a moderate amount of astigmatism which is only really a
problem when using a telescope. I can never focus stars to anything
like a sharp point once the exit pupil gets bigger than say 3mm.

Whats the best solution?

I already have spectacles which I normally only use when driving the
car at night.
I would prefer to not use them as I observe from my light poluted back
yard and reflections off them are a bother.

Contact lenses maybe ?

My understanding is that contact lenses do not correct astigmatism very
well. I wear glasses (high quality, anti-reflection coated; Zeiss "Lantal"
lenses are the best I've found). And I use eyepieces with long eye relief
(Tele Vue Radian).

You can get an eyeglass maker to make lens elements that you can somehow
attach to your eyepieces to correct astigmatism. You will then have to get
the eyepiece oriented just right in order to use it.

There is at least one manufacturer (Clear Vue optics?) that has advertised
on Astromart about an astigmatic corrector that attaches to an eyepiece much
as a filter.

http://home.earthlink.net/~clearvue1/index.html

david

Geoff wrote:

My eyes suffer a moderate amount of astigmatism which is only really a
problem when using a telescope. I can never focus stars to anything
like a sharp point once the exit pupil gets bigger than say 3mm.

Whats the best solution?

I already have spectacles which I normally only use when driving the
car at night.
I would prefer to not use them as I observe from my light poluted back
yard and reflections off them are a bother.

Contact lenses maybe ?

Hi,

There are two new non-surgical procedures out which will eliminate most eye
problems with the exception of Presbyopia. One of them, called CRT is
already out but it's not permanent. The other, called Corneaplasty, uses the
same principle but in addition, uses enzymes to "permanently" reshape the
cornea. I wrote "permanently" because the nature of the treatment makes it
reversible. This is the one I'm waiting for - it is still not approved by
the FDA.

In the meantime, I use very small, close to the face, Schott glass,
multicoated Zeiss eyeglasses. You'll need to sign a waiver because the glass
is not impact resistant and OSHA doesn't like that. They work very well.

I tried contact lenses, which I still use for other activities, but they
don't work very well for me. Astigmatism is corrected by the use of Toric
lenses and they are dependent on exact placement and orientation for
correction. All contact lenses move around some when you blink your eyes and
this results in a momentary loss of correction while the lens finds its
place again. Although not a problem at all during normal wear, I find this
annoying at the eyepiece.

Lastly, as you shorten the focal length of the eyepiece you will reach a
point at which the exit pupil will be small enough to void your astigmatism.
At that point you wont need correction. I did a test where I made a number
of artificial stars using a bright red LED where I varied the pinhole
diameter in 1mm increments. I tested my right eye in a pitch black walk-in
closet, varying the pinhole diameters until I could see a perfect star
pattern with a single diffraction ring. It turns out that in my case the
exit pupil has to be 1mm or less without glasses.With glasses I can see a
perfect pattern all the way up to 3mm (highest I tested). Armed with this
information I went to the telescope and sure enough, I don't need my glasses
for my 7mm Nagler, which happens to be the shortest focal length and the
only short eye relief eyepiece I own.

Hope this helps.

Take Care,

JAS