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yelsac    155

Quick question I've been thinking about for a while-

I'm short sighted & I have a slight astigmatism in both eyes (awful eyesight!). I normally wear contact lenses but have (thick lensed!)glasses to. So my question is when observing through a telescope will my astigmatism effect the image I'm seeing? Also would it be best to view with contacts, glasses or without either?

thanks

yelsac

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dweller25    867

I am the same as you and always view with glasses on - but my planetary drawings compared to my wifes still show I am getting astigmatism at the eyepiece !!

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James    1,063

Best bet is, imho, to try with glasses first - see if that works for you. You'll need eyepieces with fairly long eye relief though... If it doesn't have that then just try anyway, the short sightedness can be focused out. Not so the astigmatism. But... a fairly high power eyepiece will have a fairly small exit pupil - this may mean the astigmatism becomes less of an issue. I have one eye that is short sighted and astigmatic and one that's good - guess what, the bad eye is more light sensitive than the good eye! With a high mag view of something I barely notice the astigmatism.

You may find (and I'm only going on anecdote here) that using contacts isn't a good idea. As always, best thing to do is to try it each way and see what works :) 

 

 

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Geoff Lister    107

I am short sighted and have astigmatism, and, at 66, I have a much-reduced focal range (accommodation). I usually observe with my glasses on, but for wide-angle views, I take them off. I also find that, if I am using averted viewing of faint objects, I find it better without glasses.

Geoff

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Trikeflyer    48

I am an optometrist and the answer depends largely on how much astigmatism you have.  If you want to observe without glasses but with the astigmatism corrected then you might try asking your optician about contact lenses for astigmatism. These days they are pretty good. 

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Charic    2,012

Trikeflyer beat me too it?

I have been observing since the start with my glasses off, I just find it more comfortable with the eye snuggled into the eye guard, no stray light or wind hitting the eye, using the focuser to correct for my my near sightedness, myopia.
This just felt right, I was seeing things ok, but maybe it could get better! I know when I look at the stars without a scope, their sharper with glasses on.

My 2016 prescription read R -1.50 -1.00 x 70  &  L -0.25 -0.50 x 80 so with 1 diopter correction required for my dominant right eye, maybe I should re-learn my ways, and start using my glasses at the scope / binoculars?

Its said that for distance, be that long or short, the focuser corrects your aberration, but for astigmatism,  proper correction is required be that glasses, contacts, as the focuser alone can't help. 

I think therefore some experimentation is required the next time I go out.

Edited by Charic

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Trikeflyer    48
27 minutes ago, Charic said:

Trikeflyer beat me too it?

I have been observing since the start with my glasses off, I just find it more comfortable with the eye snuggled into the eye guard, no stray light or wind hitting the eye, using the focuser to correct for my my near sightedness, myopia.
This just felt right, I was seeing things ok, but maybe it could get better! I know when I look at the stars without a scope, their sharper with glasses on.

My 2016 prescription read R -1.50 -1.00 x 70  &  L -0.25 -0.50 x 80 so with 1 diopter correction required for my dominant right eye, maybe I should re-learn my ways, and start using my glasses at the scope / binoculars?

Its said that for distance, be that long or short, the focuser corrects your aberration, but for astigmatism,  proper correction is required be that glasses, contacts, as the focuser alone can't help. 

I think therefore some experimentation is required the next time I go out.

1 dioptre of astigmatism is significant, although it depends what you are looking at in terms of the object.  Everything is balance so there are pros and cons of wearing a correction at the eyepiece, convenience and comfort vs clarity, it's a choice, like everything in life.  I am -7.50/-1.00 in my dominant eye so to make observing practical I have my glasses on all the time.  Interesting discussion though. 

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Charic    2,012
7 minutes ago, Trikeflyer said:

Interesting discussion though. 

Very!

My choice to not wear glasses also excluded my Telrad use, due to seeing several sets of layered rings at infinity, but the glasses corrected the image. 
I have worn glasses at the scope, in the past, but just not used to it, but I now feel that I must try and  be more specific and critical as to what I'm actually seeing, maybe there is a benefit.
Maybe a shame I sold my  Delos eyepieces with their 20mm eye relief.

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yelsac    155
17 hours ago, Trikeflyer said:

I am an optometrist and the answer depends largely on how much astigmatism you have.  If you want to observe without glasses but with the astigmatism corrected then you might try asking your optician about contact lenses for astigmatism. These days they are pretty good. 

Thanks for all your comments.

Probably a silly question but does having an astigmatism mean that the object I'm viewing would be slightly blurred?

My eye prescription is R -5.50/-0.25 30.0 & L -4.75/0.75 40.0

Not to sure which one of those figures describes the astigmatism although I was told it is mild. I've always just used contact lenses (hard gas permeable) when viewing so I presume they don't correct the astigmatism only wearing my glasses will is that right?

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Trikeflyer    48
10 minutes ago, yelsac said:

Thanks for all your comments.

Probably a silly question but does having an astigmatism mean that the object I'm viewing would be slightly blurred?

My eye prescription is R -5.50/-0.25 30.0 & L -4.75/0.75 40.0

Not to sure which one of those figures describes the astigmatism although I was told it is mild. I've always just used contact lenses (hard gas permeable) when viewing so I presume they don't correct the astigmatism only wearing my glasses will is that right?

Yes astigmatism will cause blur, however, In fact the contact lenses will most likely correct your astigmatism because they are rigid. Soft lenses need to have a special astigmatism correction built in.  The astigmatism is the 0.25 and 0.75 numbers.  0.25 is negligible really, 0.75 is mild so with your lenses on it should be ok. 

Steve 

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yelsac    155
1 hour ago, Trikeflyer said:

Yes astigmatism will cause blur, however, In fact the contact lenses will most likely correct your astigmatism because they are rigid. Soft lenses need to have a special astigmatism correction built in.  The astigmatism is the 0.25 and 0.75 numbers.  0.25 is negligible really, 0.75 is mild so with your lenses on it should be ok. 

Steve 

Brilliant Many thanks for the info :hello2:

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Louis D    835

Astigmatism doesn't make stars look blurry as if out of focus.  Instead, they appear spikey at best focus because they focus to intersecting lines.  The 30 and 40 in your prescription indicate the angle between them, so not that much.  My angle is around 90, give or take, and 2.00 diopters, so stars look really bad without eyeglasses for me.  They're almost crosses instead of pinpoints.

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yelsac    155

Really interesting

As I understand it (according to my optician) astigmatism means your cornea is a little cone shaped rather than curved as normal. I suppose it will probably get worse the older we get!

thanks for the comment

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Geoff Lister    107

I now find, with advancing years, that I need normal glasses to spot through the finder, reading glasses for the handset's keys and display, and glasses-off for the best eyepiece FOV. Several of my mounts have places to hold eyepieces, but nowhere to put a couple of pairs of glasses. :hmh:

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