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yelsac

Eye Astigmatism help?

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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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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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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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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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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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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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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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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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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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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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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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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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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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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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On 11 November 2017 at 15:14, James said:

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 :) 

 

 

Available eye relief, with emphasis on "available" is important. 

How much is lost through the eye lens being recessed, the distance of its centre, any cups etc which can't be removed and also, should you choose to wear your spectacles, the Back Vertex Distance - which is the distance between your eye and front of spectacle lens. Obviously the BVD would not be an issue with contacts. 

 

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I always observe with glasses (cylindrical astigmatism of 1.75 and 3.00 in left and right eye respectively). Using long-eye-relief EPs I have no issues. Without glasses getting focus is impossible. Stars turn from horizontal to vertical stripes via a near circular blur in between. Not good at all. With glasses I have no issues.

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As Steve pointed out above, your astigmatism is rather mild and in your right eye almost negligible. If this is your dominant "observing eye", you can, IMO, correct the myopia just by focusing, without needing glasses, which would allow you even the use of eyepieces with short eye relief, e.g. Plössls. In case you would find yourself observing mostly with your left eye, you would need your glasses with astigmatism correction. Alternatively, you might use, in combination with TeleVue eyepieces exclusively, the astigmatism-correcting "Dioptrx" lenses:

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

(as a myops without astigmatism, I don't have any experiences with these, but someone on here should know, I guess)

Stephan

Edited by Nyctimene

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When I bought eyepieces, I tried to get ones with good eye relief to allow me to to use my glasses with them mainly to avoid having to take them on and off all the time. (I have a couple of Panoptics, and a couple of Vixen LVs). Mmy eyesight is about -2.5, with -0.5 CYL value in dominant eye, so all but the brightest stars are invisible with uncorrected eyes.

I have never gotten on with either make: I just couldn't get close enough, and so just pop glasses off when observing, but I guess my astigmatism is fairly mild compared to others. :dontknow:

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On 14/11/2017 at 18:32, Geoff Lister said:

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:

Geoff

Last year after struggling to thread a #22 dry fly onto a x7 tippet In the middle of a river, I realised I needed some optical assistance in addition to my polaroids.  Solution, a set of bifocal polaroids.  Was initially sceptical about using bifocals as I thought I’d struggle with them.  As it turns out they were a joy to use.  Having used them for a season I decided after one more evening of exchanging reading for distance during an observing session that I would try the bifocals in my other hobby.   Ordered a new set of glasses from SpecSavers during my recent two year eye test.   Received my new prescription last week, just in time for a weekend away with some stargazing friends at our favourite dark skies site in the Scottish Highlands.  The new specs were a real improvement.  No more having to change glasses when alternating  between distance and close focus.  Should also mention that I have significant astigmatism in both eyes:

left: -3.5

right: -2.5

so glasses are a must for me at the eyepiece ?

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I have Varifocals which are great mainly. But star gazing shows the lenses own astigmatism mainly where zones switch from reading to mid-range to distance. 

If I was to get a pair of specs for scope eyepiece viewing, would it be distance rather than closer that I need? (Also glass as scratch resistant)

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4 hours ago, 25585 said:

I have Varifocals which are great mainly. But star gazing shows the lenses own astigmatism mainly where zones switch from reading to mid-range to distance. 

If I was to get a pair of specs for scope eyepiece viewing, would it be distance rather than closer that I need? (Also glass as scratch resistant)

Correct.  If you use any wide field eyepieces and your bifocal split is set reasonably high, you don't want to use bifocals at the eyepiece because you'll see the split line as an aberration and you won't be able to focus the entire field at once.  If you want to see the sky clearly for aligning your scope to a target, you'll want a distance prescription pair of glasses.  If you tend to spend more time looking at charts or displays, you'll want a reader prescription.  Either can be focused through the eyepiece.  If you plan to show objects to others, stick with the distance glasses because most folks wear distance corrected eyeglasses, so they won't have to adjust focus much when they look through the eyepiece.

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51 minutes ago, Louis D said:

Correct.  If you use any wide field eyepieces and your bifocal split is set reasonably high, you don't want to use bifocals at the eyepiece because you'll see the split line as an aberration and you won't be able to focus the entire field at once.  If you want to see the sky clearly for aligning your scope to a target, you'll want a distance prescription pair of glasses.  If you tend to spend more time looking at charts or displays, you'll want a reader prescription.  Either can be focused through the eyepiece.  If you plan to show objects to others, stick with the distance glasses because most folks wear distance corrected eyeglasses, so they won't have to adjust focus much when they look through the eyepiece.

Thanks Louis. I think distance as naked eye sky viewing will hopefully be better too. 

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Having used my bifocals for the first time this past weekend, I can say that initially the bifocals were strange, the separation caused some issues at first, but as soon as I found the sweet spot in the distance portion, I had beautiful point source stars.  In addition the advantage of being able to consult skysafari without having to swap or remove my glasses just made the whole observing experience much more enjoyable.  I certainly wouldn’t be at the telescope without them now?

Edited by DeepSkyMan
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Have recently had both eye done with lens replacement for cataracts

Use glasses for reading and computer work

When observing do not have a need to wear my reading glasses, and everything is perfectly clear that I am observing

Eyepieces do compensate for eye sight imperfections

 

 

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Oh shoot, it never occurs to me before. I do have astigmatism as well and at times it causes slanting on my vision and leading to vertigo. I haven't thought it might be a hindrance to my stargazing experience. Good to know you brought this one. 

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