Time for Tv Dioptrx ? What do I need to know ?

[Space Hopper]

Hello all.

I've been umm-ing and arr-ing over astigmatism correctors for a while now.

I'm currently 55 and have 'distance' glasses for driving, but i've never used them for astro, and don't really want to go  down that road if i can avoid it.

When i look up to the stars without glasses, the stars look a bit contorted : no longer what i'd call sharp points of light.

Looking through the scope, its a little better with good focusing, but i often feel my own worsening eyesight is the weakest link here.

I often blame insufficient cooldown or poor atmospherics, but maybe its my eyes that are the real issue.

I only have the one scope : an F7 refractor with very good optics.

 

I binoview most of the time, and currently have pairs of Tele-vue Panoptics in both 24mm and 19mm. These are my main 'workhorse' eyepieces and they get the most use.

I also have a single 2" widefield  : a 35mm Panoptic.  

Dioptrx is compatible with then all, although i'd need adapters for the 19 & 24s

Out of interest, i also use a 12.5mm Noblex (Docter) for single eye viewing, which is exceptional. But is this due to its 'anastigmatic' design, or something else ??

 

My latest prescription lists the 'cylinder' -0.50 left eye and -0.75 right eye, so fairly weak correction is needed.

For mono viewing with the 35 Pan, or whatever else,  i always use my left eye. My left eye is my better eye.

 

I'd be interested in hearing anyones opinions here, and i apologise in advance if this topic has been covered in detail already.

Are there any issues using then for bino-viewing ?

I realise the eye-lens and eyecup will be bigger with Dioptrx installed. But my IPD is a very average 66mm and my nose is also pretty average in size, and i find binoviewing an easy pastime.

 

And would i be better off getting a slightly stronger option : say 0.75 and 1.0 so i can 'grow in to them' as i assume my eyesight will deteriorate slowly in time ?

I've quickly shopped around online and 365 Astronomy seem to be the best option price-wise (sorry FLO 😉)

Thanks in advance.

 

 

 

 

 

 

 

 

 

 

 

Edited December 16, 2022 by Space Hopper

[Carbon Brush]

I have never used a dioptrix or similar device.
Aways preferring contact lenses.

If you can get on with these, you can buy a lot of lenses for the cost of dioptrix - and use them elsewhere.

If  (when?) your eyes change, your lens prescription changes.
You are stuck with the wrong dioptrix.

If your viewing combination (scope + EP) results in a small exit pupil, astig correction is less important.
However, floaters (also often with age) become more significant.

Just my two pennorth.

David.

[Ratlet]

Not OP, but I never thought of contacts.  I'm -7.5 in each eye but I don't think I've got astigmatism.  I do find it a pain to constantly take my glasses off and on but never thought about contacts.  I view with glasses off which given my prescription means a lot of faffing about if I want to do anything else whilst observing.

Do you use daily or reusable ones?  Are you wearing them normally through the day or just for observing?

[Coco]

Only this winter my right eye see's a bright star or planet like it has a tiny comets tail but not in the left one, I wear eye glasses for reading my prescription is similar to yours but I am feeling its back to the opto's for another exam. I'm 59 soon.

Personally I will avoid a dioptrix and get eye glasses if the optrician thinks its the way forward. Go to a good optrician not a high street hard sell place.

 

 

[Space Hopper]

Personally, i've never considered contact lenses. My wife has used them for years and has 'daily disposables' but they are not cost effective really (£400 + / year)

I have used reading glasses for 10 years, and distance glasses for around 3 for driving mainly. I've tried varifocals, but couldn't get on with them at all. My eyesight is pretty average for my age really, just a normal and slow age related deterioration.

 

Regarding Dioptrx,  with them being a Tele-vue item, i would sell them on if my prescription were to suddenly change. I would expect a decent return for them second hand, like most of their gear, so no issues there really.

 

You make an interesting point with exit pupils, because mine are already pretty small. Only about 3mm fully dilated i believe. 

I think the only way to see if they will benefit me is to try them, but  i would be interested in users thoughts before i commit.

Thanks

 

[Hans Joakim]

I’m also struggling with astigmatism (about -1.25), and have considered both daily lenses and TV Dioptrx. I use glasses to correct for short-sightedness and astigmatism. I have tried to get on with contact lenses, mostly motivated by this very hobby, but struggle to get on with them. Probably I’m just paranoid about putting stuff onto my eyes… I also considered the Dioptrx, but then would have to fiddle around in the dark to have it fitted to my preferred Pentax XW eyepieces. These eyepieces sport 20 mm eye relief, but that is still just a bit shy of what I need with glasses on… 

I’m not sure what to do, but currently I prefer to observe without my glasses on (and no lenses nor Dioptrx). The attached schematic is from a post over at CN, and may give an indication of when astigmatism becomes a concern (larger exit pupils). In your case, I would think staying with EPs that give exit pupils of 2-3 mm or less should be fine?

[Moonlit Knight]

I know nothing about them other than what they do, can you use them with any kind of scope?

[Don Pensack]

The DioptRx only corrects astigmatism after the image has passed through the telescope.

It is the equivalent of a multi-coated high end pair of glasses that are polished better than glasses.

It does not correct distance vision.  If you observe with one and are myopic, you will still need infocusing to get to focus.

If you observe with a coma corrector and are myopic, you will need to move the eyepieces closer to the coma corrector lens than their normal positions if myopic, and farther if hyperopic.

Glasses may be the better alternative if you use a coma corrector due to this.

 

The TeleVue chart is somewhat liberal, as a critical observer will see astigmatism at a smaller exit pupil on that chart than is indicated.

It's a pretty good average, though, for determining at what exit pupil you might need to apply astigmatism correction.

 

The DioptRx seems to work best on eyepieces of narrower field of view (<80°) because, like glasses, they distort if you look through the lens at a sharp angle, as you might do to look at the edge of the field

in an eyepiece of 80°+ with direct vision.  And you will still need glasses to read notes or look at an atlas.

In my case, I needed correction for naked eye stars, reading my notes, and the screen on my DSCs as well as all eyepieces longer than 9mm.

Glasses were the simplest and easiest solution.  I would have needed 7 DioptRx lenses and I still would have to wear glasses away from the scope.

And, because I use a dob, every time the eyepiece changes altitude or every time I look through at a slightly different angle, the DioptRx would need to be rotated.

With glasses, they're on and done.

The DioptRx seems to be a solution for someone who pretty much has ONLY astigmatism to correct but otherwise isn't significantly near or far sighted or presbyopic, and who doesn't use ultrawide or hyperwide eyepieces.

I just wish I could get glasses made to that level of polish and coating.

Edited December 17, 2022 by Don Pensack

[Space Hopper]

Great explanation Don, much appreciated 👍🏼

[Louis D]

2 hours ago, Space Hopper said:

I've tried varifocals, but couldn't get on with them at all.

I never tried them after a friend of mine tried them and got queasy from wearing them.  He did eventually get used to them, but I don't like the idea of the constantly changing correction amount depending on where I look through them.

I've been wearing bifocals for about a decade now and have gotten completely used to them after tweaking a few things about them:

• Get big frames to push the close distance part completely below your forward line of sight, yet leaving a large enough area to be useful for close-up work.  Nothing is more annoying than having to tip your head down just to look straight ahead at a distant object.  This gets really tiresome driving in a hurry.
• Back-off the near focus distance from 8 to 12 inches to about 20 to 24 inches.  Now I can clearly see my car's dashboard, read printed material on a tabletop, and read store shelves from a normal stand-off distance.  Luckily, I have 20-15 corrected vision, so I can read a bit further out than most folks.  Also, stairs are not completely blurry with the greater focus distance which freaked me out the first time I wore bifocals with normal reading distance (8-12 inches) correction.

For astronomy use, I wear single vision distance-only glasses.  I can't stand seeing the bifocal line of my daily wearers in my ultrawide field eyepieces.  The pair is only used for astronomy, so it doesn't accumulate microscratches from cleanings and daily abuse.  I got them in the lowest index plastic lens available to reduce chromatic aberrations with off-axis rays.  I bought them from an online retailer for a very reasonable amount out of pocket.  So far, I have no complaints about them.

I will admit I am lucky in that my uncorrected, yet fixed, focus distance is about 12 inches, so I can just look under my distance only glasses to read the large, blocky characters on my DSC screen.  I'm just dealing with astigmatism blurring at that point, which I can squint out in large part.

1 hour ago, Don Pensack said:

I just wish I could get glasses made to that level of polish and coating.

That would be nice, but they'd be heavy (glass).  I wore glass eyeglasses back in the early 80s, and they were always slipping down my nose.  I will admit to taking my uncoated distance-only glasses off sometimes to see if reflections are coming from my cornea, eyeglasses, or eyepiece.  Often, it is the eyeglasses, and I have to cup my hands to block the external light source.  At a truly dark site, I would imagine this to be far less common.  Yes, there is the issue of transmission; but again, you could flip your glasses off to see if there's a brightening in the field due to a DSO not visible with eyeglasses on.

[great_bear]

I use one. 

I was going to say I got it a couple of years ago, but I just checked and it was nearly eight years ago!

My one is 0.75

I got it for my 17.3mm Delos when used in my F6 Dob. It’s easy enough to use - just defocus on a star, rotate until the diffraction rings are circular not oval, and you’re done. 

There are a few annoyances:
- With a Newtonian, you need to rotate it (of course) as you raise the angle of the scope in order to keep it aligned
- The letters that are printed on the side to help with alignment are on the lower ring, not the upper one with the glass on, so if you remove and replace the Dioptrx then the lineup will have changed a little depending how tightly you’ve closed the mechanism
- When you remove it, chances are you’ll want to replace the eye guard before others use the eyepiece. This involves peeling it off the Dioptrx (easy) and stretching it back onto the eyepiece (hard - especially in the dark)

Now I’ve got it, I’ll keep it, but if I were to go back in time and reconsider - knowing what I know now - I probably wouldn’t buy one. Here’s why:

- For those like me, who need 0.75, it only makes a difference to eyepieces with a 3mm or greater exit pupil 
- You might not need it when using those eyepieces in a different (slower) scope
- It only fits Tele Vue eyepieces
- You only notice it on brighter stars
- Even if you have more than one eyepiece to apply it to, do you really want to keep unscrewing and refitting it every time you swap low-power eyepieces whilst observing?
- If not, would you buy one-per-eyepiece instead? (unlikely)

In my case, all it’s really done is make the Delos 17.3mm £100 more expensive for a marginal gain in sharpness - and even then, only on a scope that I don’t use at home (and rarely use elsewhere, for that matter).

Overall then, not my smartest purchase. 

Edited December 17, 2022 by great_bear

[Don Pensack]

Jeremy,

The DioptRx also fits:

--most ES eyepieces

--Baader Hyperions

--Baader Hyperion Zoom

--Baader Morpheus

--Pentax XW

--APM UFF 24mm

--APM Hi-FW 12.5mm

--APM Super Zoom

And I'm sure a lot of others.

Basically, any eyepiece with at least a 2mm long top section 41-43.9mm in diameter.

It can even be made to fit other eyepieces in various creative ways.

[Moonlit Knight]

12 hours ago, Don Pensack said:

The DioptRx only corrects astigmatism after the image has passed through the telescope.

It is the equivalent of a multi-coated high end pair of glasses that are polished better than glasses.

It does not correct distance vision.  If you observe with one and are myopic, you will still need infocusing to get to focus.

If you observe with a coma corrector and are myopic, you will need to move the eyepieces closer to the coma corrector lens than their normal positions if myopic, and farther if hyperopic.

Glasses may be the better alternative if you use a coma corrector due to this.

 

The TeleVue chart is somewhat liberal, as a critical observer will see astigmatism at a smaller exit pupil on that chart than is indicated.

It's a pretty good average, though, for determining at what exit pupil you might need to apply astigmatism correction.

 

The DioptRx seems to work best on eyepieces of narrower field of view (<80°) because, like glasses, they distort if you look through the lens at a sharp angle, as you might do to look at the edge of the field

in an eyepiece of 80°+ with direct vision.  And you will still need glasses to read notes or look at an atlas.

In my case, I needed correction for naked eye stars, reading my notes, and the screen on my DSCs as well as all eyepieces longer than 9mm.

Glasses were the simplest and easiest solution.  I would have needed 7 DioptRx lenses and I still would have to wear glasses away from the scope.

And, because I use a dob, every time the eyepiece changes altitude or every time I look through at a slightly different angle, the DioptRx would need to be rotated.

With glasses, they're on and done.

The DioptRx seems to be a solution for someone who pretty much has ONLY astigmatism to correct but otherwise isn't significantly near or far sighted or presbyopic, and who doesn't use ultrawide or hyperwide eyepieces.

I just wish I could get glasses made to that level of polish and coating.

Excellent, thank you.

[Shimrod]

15 hours ago, Space Hopper said:

Personally, i've never considered contact lenses. My wife has used them for years and has 'daily disposables' but they are not cost effective really (£400 + / year)

 

I'm an occasional contact lens wearer. I get 10 pairs a month which costs £162 a year. You do get a couple of benefits (Specsavers) - free eye test and £85 towards a new pair of glasses every two years, so the real cost is potentially much lower.

On the occasions when I observe without lenses in I get very frustrated removing and replacing glasses while getting everything set up (I am short sighted and can't make out many stars without corrected vision).

My challenge now is that I need reading glasses when I have my contact lenses in!

[great_bear]

Contact lenses make the brightest stars look a bit of a mess. Instead of sharp pinpricks of light they bloat (at least with the brands I’ve used) into a bunch of fuzzy diffraction spikes. 

Edited December 17, 2022 by great_bear

[great_bear]

4 hours ago, Don Pensack said:

Basically, any eyepiece with at least a 2mm long top section 41-43.9mm in diameter.

Perhaps, but without a lip similar to Tele Vue, you will lose the combination of free rotation with secure fitting. I wouldn’t want to knock the thing off the top of the eyepiece whilst clumsily adjusting it with cold hands.   

You could screw it tight and spin the whole eyepiece in the focuser I suppose - but that may be tricky when using eyepieces with screw up/down eyeguards, which is quite common in the longer focal length category. 

4 hours ago, Don Pensack said:

It can even be made to fit other eyepieces in various creative ways.

Yes - I have given serious thought to superglueing a Nagler Dioptrx adaptor onto the tops of my SWA and Aero ED eyepieces to do just that.

[great_bear]

3 hours ago, Shimrod said:

My challenge now is that I need reading glasses when I have my contact lenses in!

I’m in the same boat - but a cheap pair of reading glasses from (literally) Sainsbury’s does the trick. As stated above I don’t use contacts during astronomy because I prefer the look of stars without them. 

Edited December 17, 2022 by great_bear

[Second Time Around]

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. 

But making many eyepieces compatible with a Dioptrx is often pretty easy and leads to increased sales.  

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 0.25 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 finderscope eyepiece, but even if I didn't I don't find astigmatism critical on a finderscope as it's doing just that - finding

9) On the rare occasions I share my scope I 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

Edited December 18, 2022 by Second Time Around
Changed finder to finderscope

[Second Time Around]

Quote:

"Perhaps, but without a lip similar to Tele Vue, you will lose the combination of free rotation with secure fitting. I wouldn’t want to knock the thing off the top of the eyepiece whilst clumsily adjusting it with cold hands.   

You could screw it tight and spin the whole eyepiece in the focuser I suppose - but that may be tricky when using eyepieces with screw up/down eyeguards, which is quite common in the longer focal length category. "

 

Many eyepieces have a 43mm screw top under the eyecup.  If you put a 42mm x 2mm o-ring or elastic band over the threads, not only is the Dioptrx held securely, but you can also rotate the Dioptrx to vary the angle.

It's even better with a 42mm (T2) thread; then you don't even need the o-ring or elastic band for the Dioptrx to rotate.

The first pic below shows such an elastic band attached to a Baader zoom; the second shows my holding the Dioptrx without the eyepiece falling off.

A final tip: put a tiny bit of glue or Blutac at the 12.00 position on the outer rim of the Dioptrx.  That way you can quickly and easily get the correct angle for the Dioptrx when changing altitude on a Dobsonian etc.

 

 

Edited December 17, 2022 by Second Time Around

[Carbon Brush]

Another comment to throw into the mix.

Any glasses move your eye away from the scope, requiring an eyepiece with long eye relief.

If you are long/short sighted, without astig, you can use a scope without glasses. Just refocus.

If you try to use varifocal glasses with a scope, you can usually forget about good views.
OK if the specs lens is big and near/far correction difference isn't large you can get away with it.
But if you have say 2D difference between near and far, and have some astig, and small specs lenses, the scope views are awful.

It is for astig correction that contact lenses come in useful.

Nowadays opticians push you towards daily disposable lenses.
The arguments being that you don't have to use cleaning solutions and some people don't clean properly resulting in eye infections.
Right now I am using daily disposable and working down a large stock as I don't use them anything like every day.
However, my preference is for monthly lenses. They are easier to handle, being slightly more rigid. I am capable of handling the cleaning solution.
I know not to try to make the lenses last too long, risking things growing in them. I know to wash my hands.
A rule of thumb advised by one optician was to regard monthly lens life as 30 insertions, or 60 days from opening if worn only on a few days.

I have been very happy with the contact lens views through scopes. Far better than specs lens or tolerating residual astig.
There is no need to rotate as a reflector scope moves. If your left and right eyes have different correction, you can view using either.
Contact lenses also allow binoviewer use, without the expense of two dioptrix.

I have never compared compared contact lenses with a dioptrix. Maybe I should give it a go if I can borrow one or buy used for a good price.

Alternatively spend on the imaging or EEVA side of things and view on a big screen😄.
 

[Don Pensack]

11 hours ago, great_bear said:

Perhaps, but without a lip similar to Tele Vue, you will lose the combination of free rotation with secure fitting. I wouldn’t want to knock the thing off the top of the eyepiece whilst clumsily adjusting it with cold hands.   

You could screw it tight and spin the whole eyepiece in the focuser I suppose - but that may be tricky when using eyepieces with screw up/down eyeguards, which is quite common in the longer focal length category. 

Yes - I have given serious thought to supergluing a Nagler Dioptrx adaptor onto the tops of my SWA and Aero ED eyepieces to do just that.

No eyeguards are in the way when a DioptRx is used.  Any/all eyeguards are removed prior to mounting a DioptRx.

And it is true that, when used on some eyepieces, the turnability of the DioptRx is compromised and turning of the eyepiece is required.

That has no effect on the eyepiece, though, since the only eyeguard that can be used is the round one on the DioptRx, which doesn't have a direction.

It's a simple flip up/flip down type.

[Don Pensack]

8 hours ago, Second Time Around said:

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. 

But making many eyepieces compatible with a Dioptrx is often pretty easy and leads to increased sales.  

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 0.25 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 if I didn't 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 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

1. True.

2.True

3.True, though in my experience the rubber eyecups don't scratch the glasses.

4.True, though you have to adjust it every time the scope is moved unless the scope is a refractor or SCT.

5.And that is easy to accomplish with the DioptRx, though they are eliminating the quarter diopter steps in favor of half diopter steps.

6.Like many presbyopic observers, if I use the telescope without glasses, neither the sky nor my notes are in focus. So I need to put glasses on to look at the sky or my notes or my DSC screen.

I might as well wear the glasses at the scope, too, because that way I can share the view with others, whether they wear glasses or not, and I don't need any extra optics.

7.You're lucky.

8.That depends what you use a low power eyepiece for.  If it's for large star clusters, then astigmatism is contraindicated.

9.Exactly.

10.I have compared as well, but I don't see a difference, though I do see a difference between eyepieces.

[great_bear]

18 hours ago, Second Time Around said:

 If you put a 42mm x 2mm o-ring or elastic band over the threads, not only is the Dioptrx held securely, but you can also rotate the Dioptrx to vary the angle.

Brilliant!

18 hours ago, Second Time Around said:

A final tip: put a tiny bit of glue or Blutac at the 12.00 position on the outer rim of the Dioptrx.  That way you can quickly and easily get the correct angle for the Dioptrx when changing altitude on a Dobsonian etc.

Also brilliant!

[Space Hopper]

To Jeremy, Steve and Don & others, a big thankyou to you all for your contributions here 👍🏼

As i don't use a Newtonian and mainly use mid angle fov Panoptics I think they are worth me trying out.

I'm looking at trying them with my binoviewing 24mm Panoptics....possibly using 0.75 and 1.0 Dioptrx, rather than my current 0.50 and 0.75 current prescription,

and also ordering a 0.75 for my 35 Pan as well. Not pressed the order button just yet, though. 365 Astronomy seem the best price so far, but a 4 week leadtime.

 

[Second Time Around]

Don: re your reply to my point 9.  Rather than "finder eyepiece" I meant "finderscope eyepiece."  I've edited to say this, so thanks.

The finderscope eyepiece is one of the many 20mm/70 degree ones with a crosshair.  I've found you can replace the eyecup on these with a Dioptrx.