Astigmatism question.

[Venus_is_my_friend]

Hello my name is Neil and I have an astigmatism, it has been 23 years since it started....

Anyway none comical AA style intro aisde.

I read in a book about the Tele Vue Dioptrx and went if joyful to research it.

With the Dioptrx costing around £80 and it only fitting on Tele Vue eyepieces which are very beyond my budget, my questions are such...

1. Does any have or has anyone used the Dioptrx? If so it would be great to find out your review.

2. Does anyone know of a cheaper eypiece the Dioptrx will fit on?

3. Does anyone know of a cheaper alternative to the Dipotrx?

Thank you for reading,

Be safe and warm,

Neil

[Carbon Brush]

Hi Neil.

I don't wish to pry. But can the astigmatism be corrected by either spectacle or contact lens? Some opticians recommend a combination of both to correct complex conditions.

David.

[Cellarman]

Nearly everyone who wears spectacles has astigmatism to some degree. How much and at what axis is yours?

As David said in the previous post, it can normally be corrected.

[Capricorn]

Sounds as if you have sufficent astigmatism to be noticeable, in which case I assume you have glasses or contacts. I have astigmatism and glasses.

Get long relief eyepieces and keep the glasses/contacts on. They are then doing the compensation necessary/required.

[NGC 1502]

Dioptrx review is here http://www.skynews.ca/PDFs/Review_PDFs/Dioptrx-dec05.pdf

HTH, Ed.

[Venus_is_my_friend]

Thank you for your replies.

My astigmatism is bad! hehe I wouldn't know how bad or what axis. Without my specs I can't see anything in any kind of focus, very bad.

I was just pondering the world of astronomy without glasses. I used to wear contacts but I got one stuck in my eye and had to go to hospital to get it out...I can still remember the stinging so they are not my cup of tea.

The issue I have is when I use eyepieces with long eye relief and my specs on I have to cup my hand around the eyepiece to block the surrounding view out and (with and without gloves) my glasses steam up within seconds (I need to breath) making the view worse than when the neighbours security light goes off (that blumming dog!). When I look with my glasses off I don't get the steaming (duh) but the view is not as crisp as with the first 5 seconds from when I keep my specs on.

Any tips?

Neil

[BenM]

You can use the dioptrix or your glasses and Radian eyepieces. For fogging, try an anti-fogging wipe which is basically a surfactant that disperses the condensing moisture so that it doesn't form little droplets that act like many tiny lenses obscuring your view but instead it forms a thin film you can see clearly through. You can try it without buying anything you don't already have; take a pin-head speck of dish soap and rub it on the inside of your eyeglass lens to coat it with the surfactant. See if it fogs. I don't wear glasses but this always did the trick on my motorcycle visor, at least for a while. At some point you'll have to wipe the lens are reapply a surfactant because you're not stopping the condensation, just stopping it from forming all those little view-obscurring lenses.

[Carbon Brush]

I have some astigmatism & short sight, and am old enough to need a different 'reading' correction.

For astrophotography, I tend to use varifocal specs for the convenience of being able to see everything easily, but accept that an eyepiece view could be better than the view looking through a varifocal lens.

For direct eyepiece viewing I use contact lenses. No worries on eyepiece eye relief, the astigmatism is corrected, no steamy specs. Just some 'poundland' reading specs as required to find small fiddly things. So much easier.

Sometime opticians will do free trials on contact lenses. Worth a try?

David.

[Sp@ce_d]

I have astigmatism and I bought a Tele Vue eyepiece (8-24 click zoom) because of the availability of the dioptrx. But like you say its a significant investment road to go down and I never went further. I also thought that I'd probably end up having to replace them every time my eyes change prescription.

Around the same time I had to give in and accept I had reached the age where Varifocals were the way to go and the cost of these was more than enough! I also occasionally wear contacts. Occasional because I never found any that were stable enough for viewing computer screens/TV etc. so no use for work. My optician was very good and went to some lengths to find me contacts that were cheap enough specifically for me to use with the telescope.

However, most of the time I use my glasses and like you say cup a hand around if needed. I have thought about making some sort of shield or investigating rubber eye cups. Something that is large enough to still allow a bit of air flow perhaps.

The Tele Vue is nice though!

[pleiades]

3. Does anyone know of a cheaper alternative to the Dipotrx?

Hi Neil

Below is a method friends with astigmatism applied to eyepieces. You can ask some optician to cut for you a circular lens with your degree of astigmatism. Easily can cut it and cost is very small .

Test the axis: Aim a star in the center of field, and unfocus. Because of astigmatism you must see star to be elliptical. Put the astigmatism lens on top of your eyepiece, and turn it until you see the star has a circular icon. Fit it there. Focus normally.

Hold in place: If your eyepiece(s) has rubber eyeguards, it's easy to fit the lens, and let the rubber keep it in place tight. Or else, you have to glue it on the circumferential surface if possible. You don't have to use a strong glue. Just keep it in place.

Some, glue it on the eyepiece lens with a drop of cedarwood oil. Better to be the last solution if anything else can't fit. Also a lot of cedarwood oil will work like another lens, so better to find some other method to keep it in place.

Use: Every time before your observation, you have to do the test with the star to find the corrected axis of astigmatism. Just turn the eyepiece until you find the best viewing orientation. Or you can mark eyepiece and focuser for the right position (if you don't have to pivot the OTA, i.e as in Newtonians on a equatorial base).

This method is also very good for binoculars and the rubber eyeguards of them.

Perhaps the most difficult matter is to find an optician to collaborate and catch the point easily.

[Venus_is_my_friend]

Thank you everyone, there are some great ideas for me to look into, keep them coming though.

BenM:-

That washing up liquid sounds like a good idea to give it a go and cheap. Does it last an entire night or will it need re-applying ever few hours. Sorry if the question seems lazy on my part, I am working away and don't have access to washing-up liquid. If you don't know bhe assured I will be testing it when I get home.

DavidValentine:-

I used to wear contact lens and once got on stuck in my eye, after trying for 3 hours and even letting others try to get it out I had to go to hospital. It stung like mad and as of that day me and contact lens fell out.

Sp@ce_d:-

Which eyepieces are you able to compare the Televue to. I have considered buying a very expensive eyepiece such as the TeleVue but didn't know how much better it was and if it was worth the money.

Pleiades:-

That does sound somewhat beyond my skills. I might look into it though. It would be good to be able to design something that could hold the lens in place so it could easily be removed for others to look down the eyepiece, hmm. You have my design head working overtime now.

Thanks again for all the great ideas, like I said please keep them coming.

Neil

[JamesF]

If the washing up liquid trick works then I believe you can get "proper" surfactants that will last much longer. May be worth talking to an optician about to see if they can recommend anything as it could be that the ones available for motorcycle helmet visors, for example, wouldn't be suitable for spectacle lenses if they have any special coatings or something like that.

I should admit that I speak from a position of minimal knowledge as I've never bothered with any of the rain dispersants on my helmet visors and whilst my wife and son wear glasses, I don't.

James

[Sp@ce_d]

Thank you everyone, there are some great ideas for me to look into, keep them coming though.

Sp@ce_d:-

Which eyepieces are you able to compare the Televue to. I have considered buying a very expensive eyepiece such as the TeleVue but didn't know how much better it was and if it was worth the money.

Neil

All my others are Meade.. 26mm super plossl, Series 5000 9mm and ultra wide angle 6.7mm. The Tele Vue gets used the most.. I find it the most comfortable to use with glasses and for brigtness/view. Its discontinued now but here's one..

Televue 8-24 Click-Stop Zoom - Dioptrx Ready - OPT Telescopes

I actually got the click version because I had some crazy idea I might want a pair for use with a bino viewer until I saw how much they were!!!

I also have a Tele Vue powermate 2.5x which I think is nice and bright too. But I do have limited experience of trying any other eyepieces.

I was going to mention the "Buy and Try" scheme post, but realise it was you that posted it! .. Doh. I've not looked at that site but I see it's down till FEB.

[Ags]

I have read somewhere that astigmatism is less noticeable with smaller exit pupils. So viewing planets at high magnifications (which results in small exit pupils) also removes the need to correct for astigmatism in many cases.

Astigmatism would remain an issue when viewing DSOs or the moon at lower magnifications.

Here's a reference:

Dioptrx astigmatism-correcting accessory lenses

[haitch]

Do you have problems with all your EPs? Just that the shorter the focal length the smaller the exit pupil and, hence, the less noticeable astigmatism tends to appear. if you go the getting a lens from the optician route you might find you only need it on your longer EPs.

Edit: Beat me to it whilst I was typing Ags