Eyepiece for two roles

[W0nderste]

Hi,

For planetary and lunar viewing I've got an F10 SCT and a number of 1.25 EP's but I'm after a new 25mm EP.

I also have a SW72ED (F6) as a travel scope but also to potentially dabble in AP.  I have 2" Panaview 70* 32mm eyepiece with it, but I'd also like a slightly higher power for lunar viewing on my travels.

so my thinking is to get a 1.25" 24/25mm EP with a nice wide field of view that can be used as my 25mm on the SCT but also for good views with the SW72ED

so far I've identified the Explore Scientific 62* 24mm EP, but they are currently out of stock.

can anyone think of any other EPs that would meet my criteria??

thanks in advance

 

[Louis D]

As far as 1.25" eyepieces in that range, I have the 24mm APM UFF, 25mm Meade HD-60, 25mm BST Starguider (Paradigm), 23mm Aspheric 62°, etc.  I'm assuming you're wanting to stay within 1.25" eyepieces.  The 24mm ES-68 is also well thought of as is the 24mm Panoptic, but neither have enough eye relief for me.

1. Do you need long eye relief for astigmatism in your observing eye?
2. What is your budget?

Below are some of my eyepieces in that range imaged through an AT72ED similar to yours:

The Meade MWA is really a 25mm, so it fits your criterion if 2" is okay and you can find one.  They've been discontinued along with the HD-60 series.

[Virtus]

I have and would recommend the APM 24 UFF. It's available under several other brands - the Orion version can be used as both 1.25" and 2".

[Don Pensack]

3 hours ago, Virtus said:

I have and would recommend the APM 24 UFF. It's available under several other brands - the Orion version can be used as both 1.25" and 2".

Yes, APM Ultra Flat Field, Altair Ultra Flat, Orion Ultra Flat, Meade UHD, and Celestron Ultima Edge, 

Especially recommended if you need to wear glasses at that focal length.

Edited May 26, 2021 by Don Pensack

[W0nderste]

17 hours ago, Louis D said:

As far as 1.25" eyepieces in that range, I have the 24mm APM UFF, 25mm Meade HD-60, 25mm BST Starguider (Paradigm), 23mm Aspheric 62°, etc.  I'm assuming you're wanting to stay within 1.25" eyepieces.  The 24mm ES-68 is also well thought of as is the 24mm Panoptic, but neither have enough eye relief for me.

1. Do you need long eye relief for astigmatism in your observing eye?
2. What is your budget?

Below are some of my eyepieces in that range imaged through an AT72ED similar to yours:

The Meade MWA is really a 25mm, so it fits your criterion if 2" is okay and you can find one.  They've been discontinued along with the HD-60 series.

Thanks Louis,

i do have an astigmatism prescription but I don't wear my glasses for observing and have no idea how astigmatism effects viewing and/or how much 'eye relief' is best.

Out of interest, how do you take the pic of rulers.  I assume that is an indication of the apparent field of view or something?

 

[W0nderste]

5 hours ago, Don Pensack said:

Yes, APM Ultra Flat Field, Altair Ultra Flat, Orion Ultra Flat, Meade UHD, and Celestron Ultima Edge, 

Especially recommended if you need to wear glasses at that focal length.

Are these all the versions of APM?

[Louis D]

1 hour ago, W0nderste said:

Are these all the versions of APM?

All are optically the same internally with different barrel designs outside.  I've also read that some of the heavier versions (e.g., Altair) use a stainless steel barrel instead of aluminum like the APM.

[Louis D]

1 hour ago, W0nderste said:

Out of interest, how do you take the pic of rulers.  I assume that is an indication of the apparent field of view or something?

It's fully described in my original images thread in two posts.

 

Edited May 26, 2021 by Louis D

[Louis D]

1 hour ago, W0nderste said:

i do have an astigmatism prescription but I don't wear my glasses for observing and have no idea how astigmatism effects viewing and/or how much 'eye relief' is best.

It's based on exit pupil which is the eyepiece focal length divided by the telescope's focal ratio, and diopters of cylinder correction on your prescription.

Tele Vue's Dioptrx page has a nice diagram for estimating when you'll need correction based on exit pupil and number of diopters of cylinder (astigmatism) correction that I've repeated below:

The upshot is that if you have mild (0.5 diopters or less) astigmatism, you probably won't notice it except at the largest exit pupils when working at low powers with smaller f-ratio scopes.  If you have strong astigmatism (2 diopters or more like I do), you'll probably need to wear your eyeglasses or use a Dioptrx at all but the very smallest exit pupils when working at very high powers.

[W0nderste]

Hi Louis, 

i really appreciate the reply, although I'm not really sure I understand it.

so my right eye cylinder is 3.25 (that's my good eye...lol) so according to the chart I will see astigmatism in pretty much all EP's.  
but how does that manifest itself viewing as haven't really noticed anything specific

[Zermelo]

1 hour ago, Louis D said:

It's based on exit pupil which is the eyepiece focal length divided by the telescope's focal ratio, and diopters of cylinder correction on your prescription.

Tele Vue's Dioptrx page has a nice diagram for estimating when you'll need correction based on exit pupil and number of diopters of cylinder (astigmatism) correction that I've repeated below:

The upshot is that if you have mild (0.5 diopters or less) astigmatism, you probably won't notice it except at the largest exit pupils when working at low powers with smaller f-ratio scopes.  If you have strong astigmatism (2 diopters or more like I do), you'll probably need to wear your eyeglasses or use a Dioptrx at all but the very smallest exit pupils when working at very high powers.

That's useful.

The first time I used my 30mm in my F5 scope, I thought it was a dud - seagulls everywhere. Then I tried it with my other eye and realized it was my vision, not the eyepiece.

[Louis D]

2 hours ago, W0nderste said:

Hi Louis, 

i really appreciate the reply, although I'm not really sure I understand it.

so my right eye cylinder is 3.25 (that's my good eye...lol) so according to the chart I will see astigmatism in pretty much all EP's.  
but how does that manifest itself viewing as haven't really noticed anything specific

Mostly you'll see spiky stars instead of round stars no matter how much you try to bring it to best focus.  The spikes also rotate with your head if you pivot it around the axis of the eyepiece.  This same effect also blurs low contrast details on planets and makes resolving globular clusters difficult.

To see the effect for yourself, try looking through an eyepiece at a well focused, bright star with either eye without glasses (may need refocusing between eyes), and then repeat the experiment after refocusing while wearing your eyeglasses.  At 3.25 diopters of cylinder, you should see a dramatic improvement in the appearance of stars with eyeglasses.

For us astigmatism sufferers, I recommend sticking with longer eye relief eyepieces and buying a dedicated pair of distance-only eyeglasses with low index plastic lenses (to reduce off axis chromatism) for astronomy.  Daily wear glasses get thousands of tiny scratches in the lenses that manifest themselves when viewing stars in my experience.  Keeping a dedicated, low-scratches pair around is really helpful.  When viewing with ultrawide field eyepieces, single vision lenses are also superior to bifocal or multifocal lenses because all parts of the field are in focus at the same time.

In the US, I've had very good luck with EyeBuyDirect buying low cost, online, single vision eyeglasses.  I'm sure there's a reputable UK equivalent.

[Don Pensack]

Much to my embarrassment, I once commented about a 30mm eyepiece that it suffered from astigmatism, only to learn that my eye had deteriorated and now had noticeable astigmatism.

When I looked through that eyepiece wearing glasses, it had remarkably improved--stars were now points to the field stop.

I think almost all humans have astigmatism with dilated pupils at night--we draw the stars as 5 or 6 pointed objects, a sign of astigmatism.  No one I have ever met sees the stars as points at night.

Most of the people I meet don't even see the stars as points with glasses on, showing their prescriptions are out of date.

It was a revelation to not only see all the stars as points with the naked eye when I first got a really good prescription, but to also see about a half magnitude fainter stars.

Those really faint pinpricks had been blurred to extinction by my uncorrected vision.

 

And that is with only 1 diopter of astigmatism.  If you have more, then glasses should be pretty much essential at the telescope for all eyepieces, favoring long eye reliefs of 18mm and longer.

 

As for a dedicated single vision pair of glasses for astronomy, I'm with Louis.  There's just one problem: I cannot then read my notes or the screen of my DSC.

I have presbyopia too, so I cannot see anything near without strong correction.  So I got a pair of large lensed glasses and had them made as bifocals with only a very small bifocal section at the bottom.

I can successfully keep the "reading" section out of the field of view when looking through the eyepiece, and use the lower section when looking at notes away from the eyepiece.

Only Costco gave me the option of choosing how tall to make the reading section.  So finding a lab to do the same for you may require a bit of research on your part if making glasses

good for astronomy.  I normally use progressives in daily life, but they sure don't work for astronomy.

 

 

[W0nderste]

Thanks @Don Pensack and @Louis D for your detailed response

my right eye is 3.25 and left eye 4.75 but I've never bothered using them for viewing.  I always wear my glasses for driving but got out of habit of wearing most of the time so just continued that into astronomy, so I will give them a go.

i recently got some new varifocals as I also now suffer from presbyopia, but I will look in getting some extra single vision glasses just for astronomy

[Louis D]

6 hours ago, Don Pensack said:

As for a dedicated single vision pair of glasses for astronomy, I'm with Louis.  There's just one problem: I cannot then read my notes or the screen of my DSC.

I have presbyopia too, so I cannot see anything near without strong correction.  So I got a pair of large lensed glasses and had them made as bifocals with only a very small bifocal section at the bottom.

I got "lucky" I guess because my eyes are fixed focus at about 8 inches, so I can generally read notes by simply looking under my specs.  My wife is like you in that she had to get bifocal computer glasses for work so she can read her monitors at 2+ feet and documents at around one foot.  My astigmatism doesn't bother me too much when reading for brief periods of time, as at a telescope.

[Zermelo]

18 hours ago, Don Pensack said:

I got a pair of large lensed glasses

sorry, I couldn't resist recalling another person whose game was changed by larger specs

(Dennis Taylor, probably not that famous in LA)

[Don Pensack]

Those are the new 100° glasses. 😆