Astigmatism Advice

[Pixies]

Hi,

Having just been diagnosed with mild astigmatism (-0.5 in my observing eye), I realise why my 30mm EP isn't performing too well for me. I didn't like wearing my specs when observing before, so would like to avoid having to wear the new ones, too.

I just saw this diagram from @Ricochetin a previous post: 

So a 4mm exit pupil is the point that astigmatism will show for me. That'll be a 24mm EP in my f6 dob.

Now - can anyone here with astigmatism confirm how that chart works? If the exit pupil is on the line between grey and blue on the graph, is that likely to still have some visible aberration? Would I be looking at a point a bit further into the blue to make sure I won't suffer from astigmatic views? E.g. a 22mm EP?

 

I guess I'm going to be looking for a wide FOV eyepiece, around 22-24mm. An Explore Scientific 24mm 82deg will have a very similar AFOV as my 30mm OVL Aero. Any other suggestions around the 2-ton mark?

[Louis D]

Right, astigmatism on the line isn't intrusive.  It's there if you defocus stars, but doesn't scream out at you in focus.

There's the 24mm ES-82 as you suggest, the 22mm Nagler T4, 21mm Ethos, 20mm ES-100, 20mm APM XWA HDC, 21mm Meade MWA, 23mm Celestron Luminos, 25mm ES-100 (close).  That's just off the top of my head.  I'm sure I'm missing some contenders.

[Kimboman]

I too have been having problems with my right eye which I always use at the telescope.

I recently purchased a binoviewer and this has really improved my viewing ,using two eyes  has really helped as you can focus each eyepiece .

Should have purchased one years ago.

[Ricochet]

Where in the field of view do you see astigmatism? Do you see it in the centre or just as you look towards the edge? If astigmatism from your eye is an issue then you will see it in a star right in the centre of the field. If you see it increasing towards the edge then I think it is likely from the eyepiece, or a combination of the eyepiece plus your eye. In the second scenario a better corrected eyepiece may provide you with better star images across the field. If your budget allows it, the best option would probably be to buy an eyepiece to which you can fit a Televue dioptrix, which would correct the astigmatism from your eye and allow you to continue to observe without glasses.

In the short term I would advise trying the 30mm Aero whilst wearing your new glasses to see if the star images are improved. 

[michael.h.f.wilkinson]

I have rather stronger astigmatism (-3.00) so just use glasses while observing, regardless of exit pupil. The Nagler 22T4 would be a good bet, I suppose, because it is a super EP with enough eye relief to use glasses if you choose to do that after all

[Carbon Brush]

My solution to astigmatism has been contact lenses. This means a free choice on eyepieces. No worries about exit pupil or eye relief.
To me that has been a very good solution. If astigmatism changes, which it can, it gets picked up on a sight check and corrected with your lens delivery.
I appreciate that some people do not get on with contact lenses.

Taking a specs route. It has to be a single vision lens. Not varifocal as you end up chasing the small lens region that gives acceptable correction.
Then you need to consider the eye relief. This limits eyepiece choice.

Or use the TV dipotrix correction. But if your astigmatism changes significantly, you need to change the glass.

HTH, David.

[bomberbaz]

Hiya, I have very bad astigmatism and so started using the TV dioptrix. However although according to the chart you haVe it should be way down to under 1mm, the truth is I don't notice any difference below 2.5mm exit pupil. I actually use my 10x30 bins (3mm exit pupil) without wearing glasses. 

So my spotter 30mm eyepiece is used with glasses and the one eyepiece that gets lots of use has the dioptrix more or less permanently stuck to it, this being the 17mm Nikon. The only other one that I use the dioptrix for is the Apm 24MM but that's an occasional use EP.

So in short, the chart is to me a guide and not a rule. Each person will have their own tolerance of astigmatism and can change thins accordingly.