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wojo
super member
Reged: 09/28/07
Posts: 148
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Hello ALL.... I have a problem with field curvature in my eyepieces, all of them, from a 5mm status, 8.8 and 14mm Meade UWA. 17mm hyperion , 23mmMeade plossel, and 38mm Q70. They are used in a 12.5 F5.3 dob. I can rule out mirror and secondary issues, and because I cannot focus it out , some in other posts have suggested it might be my eye that has the astigmatism, and shows up in the eyepiece. Do any of you use TELEVUE,S DIOPTRIX correctors ? I am interested in how well they work , and if this is a worthwhile venture. THANKS ..... WOJO
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Heitman
member
Reged: 01/26/07
Posts: 49
Loc: Colorado Springs
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Money well spent for me. I use it with my Radians and it also fits on the Hyperions and some others. I found that I like using the Dioptrx much better than my glasses.
Tim
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PST
10"f/6 dob
C6R Refractor
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kaaikop
sage
Reged: 07/13/08
Posts: 468
Loc: Ste-Therese, Canada
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I would suggest you have your eyes examined first...
Then, knowing your prescription, you can get a Dioptrx, they work for me (extremely well).
My astigmatism is 1.50, so for me any eyepiece yielding an exit pupil of 1.5 or greater, I need correction or eyeglasses.
There is a lot of interesting data on this, on the Tele-Vue website.
They also fit on my Vixen LVW's, and I understand from others that they also work on Hyperion & Stratus type of EP's.
Good luck!
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Benoit, RASC Montreal
-C 9.25XLT on EQ6 Pro / ED80SF on Portamount
-Plossls, Radians, Naglers, LVW's & Orthos.
-a pair of 7x50's
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Jim Romanski
sage
Reged: 01/02/05
Posts: 485
Loc: Guilford, Connecticut
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Quote:
I would suggest you have your eyes examined first...
This is excellent advise and not just for astronomy. I wish I didn't have to wear glasses to correct my astigmatism but I'm glad that I do.
If it turns out that you have astigmatism and you get it corrected with glasses and/or Dioptrix you'll be very happy with the results.
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Jim
17.5" Dob "Project"
13.1" Coulter
8” Cave
NP 101 on a CG-5
25x100 binos
Naglers, Ethos, etc.
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Teal'c
Indeed
Reged: 08/02/05
Posts: 3486
Loc: TN
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A curvature problem can be focused out...astigmatism can not.
My astigmatism is 1.75 (left) and 2.00 (right), but I find that for me, .25 higher works better for both eyes. Even though my astigmatism (by number) is slightly worse than what Benoit said his is, I find that a 2mm exit pupil is my cutoff.
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Etch-O-Sketch and an eraser. Although....the eraser dosn't work 
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Mark Harry
Carpal Tunnel
Reged: 09/05/05
Posts: 2492
Loc: Northeast
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I have very slight astigmatism in both eyes but it has a large effect with long focal length eyepieces. I just purchased a 24 Pan with .50 Dioptrx. It corrects the astigmatism's effect on focus, and the central ~1/2 of the eyepiece's field of view is incredible. The optometrist optimized my prescription for nighttime driving/viewing. Daytime, I don't really need glasses.
The field curvature of eyepieces cannot be focused out simultaneously across the whole field of view if you have such a problem; typically you can get the central area focused pretty well. Without glasses or Drx, the view never really gets tack sharp.
I would tend to doubt that mild astigmatism of your eye would have an effect below about 2mm exit pupil, as Teal'c states. When I get to about 17mm EP in an F/4.5 scope, I don't really notice it as an issue. That's around 4mm, but that's just my situation.
Mark
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Scopes in the works-
Too many for putting down here! Favorites- 8" F/6, 8" F/4.72, 4.5" F/5.4, 14" F/4.455, all completed.
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Teal'c
Indeed
Reged: 08/02/05
Posts: 3486
Loc: TN
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"The field curvature of eyepieces cannot be focused out simultaneously across the whole field of view if you have such a problem; typically you can get the central area focused pretty well. Without glasses or Drx, the view never really gets tack sharp."
Correct! I should have made my response more clear.
My old 35mm pan suffered from this in my f/6 480mm APO triplet. David Nagler confirmed that it was a trade off in the design...and the scope design added to the problem.
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Etch-O-Sketch and an eraser. Although....the eraser dosn't work
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AstroPhethean
member
Reged: 03/04/08
Posts: 21
Loc: Aberdeen, UK
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Related question: can laser eye surgery correct astigmatism?
I know it could potentially damage your night sensitivity, but I don't want to drag the thread off topic...
Cheers
Andrew
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Observing kit:
16" Lightbridge
7mm TS Planetary, 8.5-12mm Antares Speers-WALER, 18mm Meade S5K UWA, 32mm TV Wide Field.
Set of 4, 6, 10 and 16mm Zeiss Abbe-II orthoscopics and 2x Abbe barlow in a beautiful walnut case.
Imaging kit:
Skywatcher 8" newtonian and Orion ED80 side-by-side on EQ6.
Sony alpha-300, Atik 1-HS and 2-HS CCD; Minolta Film SLR.
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Jim Romanski
sage
Reged: 01/02/05
Posts: 485
Loc: Guilford, Connecticut
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Quote:
Related question: can laser eye surgery correct astigmatism?
I know it could potentially damage your night sensitivity, but I don't want to drag the thread off topic...
The original post was about astigmatism so I don't think you're off topic.
The answer to laser surgery is "yes" it can correct for astigmatism. I don't think it's night vision per se that it spoils. There was a very good Sky and Telescope article on laser eye surgery about a year and a half ago. At that time the conclusion was that some people who have even the latest proceedure end up seeing halos around bright lights at night.
This made me shelve any thoughts of doing it myself. But the proceedures continue to evolve so who knows. I sure would love to toss my glasses even if I still needed some to read.
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Jim
17.5" Dob "Project"
13.1" Coulter
8” Cave
NP 101 on a CG-5
25x100 binos
Naglers, Ethos, etc.
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AstroPhethean
member
Reged: 03/04/08
Posts: 21
Loc: Aberdeen, UK
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Thanks Jim!
Never heard that haloes thing...
Andrew
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Observing kit:
16" Lightbridge
7mm TS Planetary, 8.5-12mm Antares Speers-WALER, 18mm Meade S5K UWA, 32mm TV Wide Field.
Set of 4, 6, 10 and 16mm Zeiss Abbe-II orthoscopics and 2x Abbe barlow in a beautiful walnut case.
Imaging kit:
Skywatcher 8" newtonian and Orion ED80 side-by-side on EQ6.
Sony alpha-300, Atik 1-HS and 2-HS CCD; Minolta Film SLR.
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deSitter
scholastic sledgehammer
Reged: 12/09/04
Posts: 779
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deSitter's home remedy for astigmatism:
Take your index finger on the opposite hand to your observing eye and apply VERY gentle pressure to the bottom eyelid, at the place where the eyelid meets the cheek. Experiment some and soon you'll find a place and a pressure at which you can warp your cornea just enough to cancel any native astigmatism. After some practice it becomes second nature. Try it on terrestrial objects first to get in the ballpark.
-drl
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kaaikop
sage
Reged: 07/13/08
Posts: 468
Loc: Ste-Therese, Canada
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Hey, it actually works!!
At first, I thought... hmmmm, yeah right... 
I have no clue why, but it's important to use the finger for the hand opposite from the observ. eye,
doesnt work otherwise.
Cool, good to know! 
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Benoit, RASC Montreal
-C 9.25XLT on EQ6 Pro / ED80SF on Portamount
-Plossls, Radians, Naglers, LVW's & Orthos.
-a pair of 7x50's
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Mark Harry
Carpal Tunnel
Reged: 09/05/05
Posts: 2492
Loc: Northeast
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-UGH!- Just about stuck my finger in the eyeball- winds up, my pressure point is right at the outside corner!
********
(Does work, though!)
M.
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Scopes in the works-
Too many for putting down here! Favorites- 8" F/6, 8" F/4.72, 4.5" F/5.4, 14" F/4.455, all completed.
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Jeff Morgan
Carpal Tunnel
Reged: 09/28/03
Posts: 1533
Loc: Prescott, AZ
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Quote:
A curvature problem can be focused out...astigmatism can not.
My astigmatism is 1.75 (left) and 2.00 (right), but I find that for me, .25 higher works better for both eyes. Even though my astigmatism (by number) is slightly worse than what Benoit said his is, I find that a 2mm exit pupil is my cutoff.
Going a bit stronger is good advice. In your docs office, the lighting will be much much stronger than night sky, so your pupil will be smaller.
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Jeff Morgan
Prescott, AZ
Wile E. Coyote School of Telescope Making
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