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Help! Visual observing with astigmatism


JeremyS
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A few evenings ago I was using the finder on my new Mewlon and found I couldn’t focus it. Stars were elongated crosses and Jupiter was a mush with no moons. Initially suspecting the optics, I eventually discovered it was a problem with my right eye. Left was fine.

A visit to the optician has revealed significant astigmatism in that eye. Much worse than previous test last November. New reading and distance glasses prescribed. I have two options, neither attractive:

1. Observe with glasses (I presume the distance pair?)

2. Train my left eye. I’m right eye dominant so this will be a pain. How long might it take and would it ever be as good as my right eye?

any thoughts? I’m must admit to feeling dry deflated about the prospects 

Also is it possible that the astigmatism is more evident at low mags and in the finder. I did find high mag views of Jupiter to be good, but maybe they would be better with glasses. So could I get away with no glasses at high mag?
 

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That's bad news Jeremy. 😟

Is it possibly worth an experiment with a TV dioptrx at your new astigmatism prescription? It may not be universal across eyepieces but worth a punt? How much has your prescription changed if you don't mind me asking?

i'm putting off the inevitable for an eye test. One year ago my astigmatism was -0.25 which i shouldn't be able to see at most normal exit pupils but i can see it so know its gotten worse...

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8 minutes ago, JeremyS said:

any thoughts? I’m must admit to feeling dry deflated about the prospects

Hi

I have astigmatism in both eyes (aging is a bitch!) and visual became so unsatisfying, so I ditched visual (not the advice you were seeking I guess) and went purely photographic. That has probably already crossed your mind, but the benefit is you can sit indoors in the warmth watching TV or doing things while the computer does all the work. Not all bad news!

Adrian

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2 minutes ago, josefk said:

That's bad news Jeremy. 😟

Is it possibly worth an experiment with a TV dioptrx at your new astigmatism prescription? It may not be universal across eyepieces but worth a punt? How much has your prescription changed if you don't mind me asking?

i'm putting off the inevitable for an eye test. One year ago my astigmatism was -0.25 which i shouldn't be able to see at most normal exit pupils but i can see it so know its gotten worse...

Excellent suggestion! Will need to see which of my TV EPs take dioptrix

I was -0.5, now -1.00 in right. Still only -0.25 in left

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1 minute ago, Varavall said:

Hi

I have astigmatism in both eyes (aging is a bitch!) and visual became so unsatisfying, so I ditched visual (not the advice you were seeking I guess) and went purely photographic. That has probably already crossed your mind, but the benefit is you can sit indoors in the warmth watching TV or doing things while the computer does all the work. Not all bad news!

Adrian

Thanks Adrian, I’m actually mainly a CCD observer, but in recent years have supplemented this with a fair amount of visual.

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14 minutes ago, josefk said:

Astigmatism is supposed to only develop (progress) slowly but i don't know exactly what that means in diopters. TV very helpfully have a chart for how much astigmatism should be visible (or rather not visible) at different exit pupils. https://www.televue.com/engine/TV3b_page.asp?id=54&Tab=_Choose 

Thanks! Amazingly helpful. So I should not encounter a problem with my astigmatism below an exit pupil of 2mm.

I have just ordered a Dioptrx from FLO. They had one on special offer.

Looks like I will need and adapter from my longer FL Nagler T6s, but Ethos should be fine. And with the Mewlon the exit pupil conditions should be even better 

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I am very sorry to hear that @JeremyS

Unfortunately I have no useful advice other than I have tried using my right eye (non-dominant one) at times and I find the longer I use it, the easier it gets, and I don't think I am loosing much (if any) detail.

Ten or fifteen minutes usually gets me comfortable (though everyone is probably different!). Not as comfortable as with my left eye but maybe it would just need more time.

Wishing you well with finding a way round it.

Malcolm

 

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21 minutes ago, JeremyS said:

Thanks! Amazingly helpful. So I should not encounter a problem with my astigmatism below an exit pupil of 2mm.

I have just ordered a Dioptrx from FLO. They had one on special offer.

Looks like I will need and adapter from my longer FL Nagler T6s, but Ethos should be fine. And with the Mewlon the exit pupil conditions should be even better 

I will be very keen to hear how you get on because i think after my next eye test i will be doing the same (it's also one of the reasons i'm buying into TV EPs - future proofing!).

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5 minutes ago, josefk said:

I will be very keen to hear how you get on because i think after my next eye test i will be doing the same (it's also one of the reasons i'm buying into TV EPs - future proofing!).

I knew there was a reason I was piling up TV eyepieces 🤣

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i have to say i don't know why the "dioptrx" style corrector approach isn't more widespread seeing as you can't correct for it with the focuser and nearly everyone over 50 will have a level of this in their vision. Possibly it's a niche of a niche but credit to TV for pioneering it TBH. I feel they definitely take a holistic system view and understand their market - short fl petzvals for wide vista views combined with a big emphasis on (and range of) wide AFOV eyepieces also for wide vista views - the only drawback to their system vision (literally) being that a decent portion of their core market are likely challenged by astigmatism with the big exit pupils that result so they correct that too. Gets my vote.

 

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I moved to long eye relief eyepieces so I could observe comfortably with my specs on.  All my eyepieces now have a minimum of 19mm eye relief and I get on fine. My rationale was that as the astigmatism gets worse with age I won’t need to keep changing the dioptrx just my specs which I would be doing anyway. 

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4 hours ago, josefk said:

I will be very keen to hear how you get on because i think after my next eye test i will be doing the same (it's also one of the reasons i'm buying into TV EPs - future proofing!).

 

4 hours ago, JeremyS said:

I knew there was a reason I was piling up TV eyepieces

Not so fast there... it's not just Tele Vue eyepieces that can take a Dioptrx... see my post from two years ago here.... 

As as already been pointed out, astigmatism worsens as the exit pupil increases, so it will be very obvious in long focal length eyepieces (particularly paired with faster scopes), finders and also larger binoculars. I last got my eyes tested about three years ago and had -0.5 dioptre astigmatism in both eyes... it's not a lot, but it I noticed it when I started using my XW40 and XW30 in my 10" dob.

I got hold off a 0.5 Dioptrx and it did indeed reduce the visible astigmatism in those eyepieces... I then also got a 0.75 a couple of years ago because it was even more perfect (likely my eyes are also getting a little worse too).

They are remarkably effective... just rotate them (they have a collar that can be rotated freely whilst firmly attached to the eyepiece) and there will be an optimum point where the astigmatism disappears or is minimised 🤞

As I usually only see astigmatism in the XW40 and XW30, I've got mine permanently mounted on those (as shown in the thread)... works well 👍

PentaxXW30_Integrated_Dioptrx.thumb.jpg.3b9575853fd3aa2f11ac378f028568ea.jpg

Edited by HollyHound
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1 hour ago, Graham Darke said:

I moved to long eye relief eyepieces so I could observe comfortably with my specs on.  All my eyepieces now have a minimum of 19mm eye relief and I get on fine. My rationale was that as the astigmatism gets worse with age I won’t need to keep changing the dioptrx just my specs which I would be doing anyway. 

This is also my rationale now too... it's why I'm favouring the XWs and (may) get rid of my remaining Ethos... I'm assuming that at some point I'll need prescription glasses for other than reading and so may choose to use those for astronomy too.... the 20mm eye relief on the XWs should help (of course Delos and DeLite also have the same too 👍

Do you find it just as easy (or almost so) to observe with glasses on 🤔

Edited by HollyHound
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I had astigmatism since the age of 6! Has always been quite bad, but stable (from memory now at around -4.5 and -5.5). I wouldn't be able to find the eyepiece without glasses on!😵

I have hence ALWAYS observed with my glasses on. It requires careful eyepiece selection (eye-relief), but tbh, I do enjoy the comfort of long eye-relief eyepieces anyway. That's why I have an almost complete set of Vixen LVs. I reckon if you want to try Delos or Delites, that may be the way forward for you - if you want to stick with Black&Greens... 😎

One other idea would be to ask your local optician if he can test your eyes dark adapted. I find that dilated pupils accentuate astigmatism more than day-time pupils. Hence, when I use my 50mm NLV, the stars are not 100% pinpoint. I may ask my optician (when I get the next pair) if he can make me one with a higher astigmatism prescription, esp. for large exit pupil eyepiece views with dilated pupils...

Generally I would not worry too much as the modern spectacle lenses are amazing compared to say even ~20years ago!

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2 hours ago, HollyHound said:

This is also my rationale now too... it's why I'm favouring the XWs and (may) get rid of my remaining Ethos... I'm assuming that at some point I'll need prescription glasses for other than reading and so may choose to use those for astronomy too.... the 20mm eye relief on the XWs should help (of course Delos and DeLite also have the same too 👍

Do you find it just as easy (or almost so) to observe with glasses on 🤔

Yes I find it very easy to observe in my glasses. Its a pain with low relief hence why I shifted. It’s second nature now. In fact I prefer my glasses on. The Delos and Delites are great. 

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Mine are bad also have been all my life. I was once told by an optician a (Dr C. Moore) that if I was used as a test subject for students in the final exam final year most would fail. Anyway good glasses work and can work well. I cant use dioptrix without stacking them and even then... 

Two things I have learnt. Get a pair specifically for astronomy which have hard coatings on the lenses and a little bit of flexibility in the frames think thin wire their just a bit more comfortable at the eyepiece. They might get a little marked up but its only the centre of the lens thats important. 

I bought a TAK 100 some years ago and have been collecting Televue Delites. Before I did, I wondered if I would see the benefits. But following the advice of members here (probably including yours) I went ahead and am thrilled everytime I use my scope. I might be missing something right at the limits but with my glasses giving me 20:20 vision I cant be missing much.

Im going to get a bino viewer soon as two eyes are better than one. If you need a better high power view you can now justify a bigger scope to overcome your astigmatism! Though how much bigger than your 180 Mewlon... and dont get varifocals.

🤓

P. S. as its only one eye we would all love it if you got a monocle.

🧐

Edited by StarryEyed
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Sorry to hear that Jeremy, but you’ll be able to find ways around it.
I believe that most Baader EPs can take dioptrx - basically any eyepiece used with a TeleVue TNVC adapter for night vision accepts dioptrx. So searching night vision on CN might reveal what others have used. I have a Hyperion 36 and BHZ (with an extra adapter from RAF Camera) I use for night vision, but I presume Morpheus might be possible too.   
However, don’t give up on training your left eye. I used to think I could only observe through one eye, but after experimenting with the other eye for a couple of hours and a bit of practice I found it was much easier than I had thought. I’m now just as happy using either. The other alternative is trying a binoviewer. Others can chip in on the implications for binoviewing if you have astigmatism in one eye, but the brain tends to compensate for vision weaknesses when you’re using both eyes. All this might require a different eyepiece strategy, but hopefully the quality of views needn’t be compromised.

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Sorry to hear of this Jeremy, but watching for the Dioptrx outcome with great interest.

Quick question: when you view Jupiter naked eye what does it look like? I guess not pin point? 

Basically a month or two ago I popped out late just to look ay the sky, and noticed that Jupiter was a tiny seagull shape. I was a bit concerned but read that if you're tired or have had a drink (both of which were true at the time) it can actually temporarily cause (or worsen if you already have) astigmatism. 

I've since noticed that this happens with Jupiter *all* the time for me, and in my lowest power EPs to some extent as well so I'm now thinking I need to get it checked out, but I'm wondering if you had a similar experience. 

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When I got my first scope after a lot of head scratching about poor images I worked out I had astigmatism.

It is exit pupil related and you should find over time at what exit pupil you notice you benefit from correction.

The Dioptrx is great but with a couple of caveats. One is it doesn't attach very securely so you have to keep that in mind. The other is it is easy to align a Dioptrx when you are looking at Vega with a big exit pupil, but the smaller the exit pupil gets and the more extended or dim the object is, the harder it gets to know the Dioptrx is correctly aligned. So labelling it with a sticker or something to know the right orientation is useful.

The best views Ive had have been with Dioptrx rather than glasses, but glasses are less workload as the orientation is always correct and you don't have to reinstall them on each new eyepiece you want to use.

If using glasses a pair that sit closer to your face is useful, glasses vary a lot in how far from your face they stick out.

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@JeremyS I too feel your pain on this, my eyesight has been blighted by Astigmatism in both eyes, but the right (observing eye) is far worse.
It came to light with me moaning about a scopes performance to another forum member when we observed together, we had the same telescopes at that time.

I then also realised I was not seeing easier doubles, the second stars never showed.

Solved with a Dioptrex, but alway had a fight to keep kit right, so now long eye relief eyepeices and glasses,
distance ones are the order of the day. It also helps me pick out dimmer objects when I look up with just the MK1's.

Add in needing readers these days and it adds a challenge to the fine art of visual astronomy.
 

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I think glasses v Dioptrx is very much a matter of personal choice.  Depending on one's eyesight there are pros and cons of each, and what's best for one person may not be the best for another. 

 

Amongst the disadvantages are:

1) Not all eyepieces accept a Dioptrx

2) If the angle of the eyepiece changes when moving the scope (e.g. a reflector), you need to adjust the Dioptrx.  The quick and easy solution is to put a small blob of glue on the rubber of the Dioptrx and always have this at say the top

3) No good when sharing eyepieces

4) You may need glasses anyway to look at the sky or charts etc

 

However, I wonder how many have tried a Dioptrx?  And of those, how many have actually done a head to head comparison?

 

These are the reasons I prefer a Dioptrx plus some comments:

1) The coatings are better than on even the top of the range Rodenstock lenses on my glasses

2) The polish is almost certainly better than that of glasses - few people would pay for this on glasses so almost no demand, so no supply

3) My glasses have plastic lenses that scratch more easily than the glass lens in a Dioptrx

4) The angle of my astigmatism changes between my annual eye tests.  With a Dioptrx I can adjust this at the telescope

5) I find that, like many, I need an extra 0.125 or 0.25 correction for astigmatism at night

6) I wear my glasses on a cord and have no problems taking them on and off for looking at the sky - it quickly becomes automatic

7) I have no presbyopia and so don't need glasses at all for looking at close range objects such as screens or maps

😎 I have a Dioptrx on my finder eyepiece, but even without this I don't find astigmatism critical on a finder as it's doing just that - finding

9) On the rare occasions I share my scope I do wear my glasses

10) And most of all, and this is the clincher, having done head to head tests I found that I can see more with a Dioptrx than with my glasses

 

As has been mentioned already many Pentax and Baader eyepieces accept a Dioptrx.  So do many from Explore Scientific.  If the eyepiece has a M42 (t-thread) or M43 screw top it'll almost certainly accept a Dioptrx.  The same goes for most others with a non-screw 42 to 43mm top.

In some cases fitting an elastic band or an O ring to the top will give a secure hold whilst still allowing the Dioptrx to be turned.  I don't find this necessary with an M42 thread, but do with an M43.

For instance Baader Mk IV zooms have an M43 screw top and need an O ring.  The O-ring has an inside diameter of 42mm and a thickness of 2 mm.   Below is a pic of my holding a Baader Mk IV zoom by a Dioptrx without the eyepiece falling to the floor.  The Dioptrx can still be turned.

816502682_BHZDioptrx2.jpg.e2931483b98c1aa573d1852ef36dfb0c.jpg

 

Edited by Second Time Around
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