Astigmatism

[Kirby301]

hi all,

In a previous post I thought I was experiencing problems with the spider vane creating spikes, this is mostly true. However, I tried doing some observing with my binoculars and was  still experiencing the spikes.

I booked into the opticians and was told I have astigmatism. Now where do I go from here?

What can I do to overcome this problem or was make it easier?

Many thanks.

[vlaiv]

Wear glasses?

Try changing your observing eye first. Eyes usually don't have same level of astigmatism. My right eye is next to useless while my left one is very sharp. Naturally I use my left (dominant) eye for observations.

Other option is no to wear them when doing high power observing. That will depend on exit pupil and how much astigmatism you have in your eye.

Impact of astigmatism often depends on exit pupil because small exit pupil uses only small portion of your eye lens and small portion will be less distorted (relative to its size) than whole lens. Often people don't notice astigmatism effects below 1mm exit pupil.

Binoculars have rather large exit pupils and you'll readily see any astigmatism you have.

[Kirby301]

Thanks for your reply @vlaiv

I do wear glasses, however not at the eyepiece. I have tried but the view isn't as good being further away.

My dominant eye is my left eye, naturally I use this one as the right one gives a bit of a hazy view.

Unfortunately my left eye is like a "rugby ball" to quote the optician. 

 

 

[Mr Spock]

The only option is glasses and long eye relief eyepieces.

I have astigmatism in my right eye, thankfully, I'm left eye dominant. If I had to observe right eyed I'd be stuggling.

[Starwatcher2001]

I'm another one with astigmatism, and spectacles. Mine is most apparent in low power eyepieces (40, 32 , 25mm) which are unusable without glasses. Thankfully (for the reasons I've just learned from @vlaiv above - thanks!), the eye-relief on the lower power eps are good enough to use with glasses. Higher power eps are useless to me with glasses (looking down a straw), but don't show my astimatism without glasses.

I've just ordered a 9mm Celestron X-Cel Lx eyepiece, which has better eye-relief to see if I that works for me with glasses. If successful I'll probably wear glasses constantly while outside to avoid swapping on and off, which is annoying when making notes and checking charts etc.

As for bins, I went for a pair of Nikon Monarch 5's which have nearly 20mm of eye-relief and work perfectly with glasses for both astronomy and terriestrial viewing.

Incidentally, you can get contact lenses that correct for astigmatism. They are "weighted" at the bottom so in your eye they naturally settle in the right orientation. I tried them for a while, but just didn't get on with contacts in general.

[Shimrod]

23 minutes ago, Starwatcher2001 said:

Incidentally, you can get contact lenses that correct for astigmatism. They are "weighted" at the bottom so in your eye they naturally settle in the right orientation. I tried them for a while, but just didn't get on with contacts in general.

They are called Toric contact lenses - I have them and they work well. However I have now reached the age where I have to wear reading glasses if I have my contact lenses in!  I only have astigmatism in my right, so tend to observe without glasses or lenses - I find my eyes object to contact lenses late at night.

[Hallingskies]

Astigmatism drove me down the imaging path!  Long relief eyepieces are helpful though, I have a set of old Vixen LVs that are quite spectacle-friendly.  I never got the hang of contacts, made my eyes sore.

[Louis D]

On 09/08/2020 at 02:31, Kirby301 said:

I have tried but the view isn't as good being further away.

Then you need to buy eyepieces with longer eye relief like Pentax XWs, Delos, DeLites, Morpheus, Vixen SLVs, etc.  Many long focal length eyepieces naturally have long eye relief.  If you use them with a Barlow or telecentric magnifier, you can get to higher powers while maintaining or even extending the long eye relief.

[Alan White]

I as many above am in the same boat.
Glasses to observe, it sharpens the sky up for star hops anyway and then Long Eye-relief eyepieces for Low and Medium powers.
High power, glasses can come off as Astigmatism for me is not an issue here.

You could also try the TeleVue Dioptrx unit on eyepieces, so not needing glasses.
This will be good for you or not, some love them, some don't.

From your prescription, you will have a  value that relates to the astigmatism, this relates to a TeleVue Chart that shows at which point 
you can get away observing without correction. 

This is based on exit pupil size.

To calculate the exit pupil of a telescope, divide the focal length of the eyepiece in millimeters by the focal ratio of the scope. For example, a 25mm eyepiece used in an f/5 scope delivers an exit pupil of 25/5=5mm, while a 35mm eyepiece in the same scope delivers an exit pupil of 35/5=7mm

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

 

 

Edited August 10, 2020 by Alan White

[Kirby301]

Thanks for all the replies.

I'm currently using the skywatcher supplied 25mm eyepiece and an 8mm bst and combine them with a 2x Barlow. I think the weakness of the 25mm is showing through with regards to eye relief.

I cant wear contact lenses, ive tried but I can't get them in my eyes, they get close and I back away.

I like the idea of the dioptrx, its an expensive option to see if it works or not, especially if its like marmite, either love it or hate it,I will look into it.

Does it fit on all eyepieces?

I would have to use the 2.5 version, shame they don't do higher 

Many thanks 

[Louis D]

Dioptrx still need about 15mm of usable eye relief on an eyepiece to work well.

It fits on eyepieces with an eye cup lip of about 41mm to 44mm in outer diameter.  This is assuming the eye cup is removable.  Many non-TeleVue eyepieces have an M43 top thread once the eye cup is removed.  Then it's just a matter of it's tall enough for the Dioptrx to cam down onto it securely.