520 replies to this topic

[Sarkikos]

Mike: If you get the opportunity to try the SM you may be pleased. One thing I've learned is everyone's accommodation, value of certain optical characteristics/qualities, telescopes used, etc, is different and make a "one size fits all" or "mine is better than yours" approach to not be generically applicable. It is similar to eye relief, just read through all these threads on how this tolerance varies almost to an individual. I've read few people mention FC as a distraction to observing objects these specialized eyepieces are intended in their use.

I often mention FC as a major aberration that I see in eyepieces and telescopes.  I am very sensitive to FC, because my eyes have virtually - perhaps no - accommodation for focus.  This means that if the eyepiece has FC I will see it.  And I read that the SM's have severe FC.  So I will not only see the FC, but chances are it will be a major distraction to me.  

 

Probably the only way that I would tolerate the FC in SM eyepieces, is if I acquire mounts that track, which I don't have now.   I don't think it would be cost effective to buy a decent tracking mount just so I can use SM's.

 

Mike

Edited by Sarkikos, 16 January 2022 - 01:21 PM.

[Sarkikos]

I did some comparisons using the 4mm ZAO II, the 4mm & 5mm Supermonos, and 5.1mm XO on Jupiter using the TEC110 over 2 consecutive nights. I was less impressed with 4mm ZAO II's sharpness and contrast when compared to the others. I was very impressed with the 5.1mm XO, since it overcame the my bias towards Supermonos. It was equal in all respects to the 4mm and 5mm Supermonos. I have never observed with the 2.5 XO.

You would like the 2.5 XO.  It is at least the equal of the 5.1 XO in optical performance.

 

Mike

Edited by Sarkikos, 16 January 2022 - 01:21 PM.

[Sasa]

You would like the 2.5 XO. It is at least the equal of the 5.1 XO in optical performance.

Mike

Yep, XO2.5 is from time to time useful even in f/20. Here is a sketch made using XO5 and XO2.5

https://www.fzu.cz/~..._30/NGC7027.jpg

[Paul G]

http://www.astrosurf...ent/tectest.pdf

They also had zero astigmatism. Astigmatism can not be removed by the tweak of a focuser knob.

 

If your mount tracks, fc is no problem at all. It can be focused out anywhere in the fov. 

Jeff, thanks, that's it. Interesting that he measured no astigmatism, while Tom Back said the eyepieces reviewed by Sky & Telescope had "severe astigmatism" initially when he got them back, later changed it to "mild astigmatism."  As a primarily lunar/planetary observer I like to see the target in its context, like Jupiter and its moons, without having to focus back and forth to see one or the other. The SMs weren't my cup of tea.

 

For lunar observing these days I almost exclusively use Ethos, love that huge expanse of the lunar surface.

[Paul G]

The ZAO II 4mm is very affected by the superficial impurity on the lens (pupil side), caused by eyelashes and tearing. I have a bad experience observing Mars, luckily I had SuperMonocentric. When I cleaned it well the quality of the ZAO 4mm was back in line with the rest of the set.

 

However, I recommend keeping the 6 mm clean too (it's not difficult, but you have to be delicate). Do not clean them in the open air even if the cloth is perfectly clean. When cleaning, arm yourself with a watchmaker's lens and luminous spotlight. For those who buy them used, check that there are no scratches, because if the dust degrades the image (they are sensitive to this), I have the feeling that the small groove of a scratch does not do less than the dust and could impact on the rendering of the image. However from experience, the maximum yield of 6mm and 4mm occurs only when they are perfectly clean (lens on the pupil side).

Since the image is concentrated in such a tiny area any schmutz on the eye lens really compromises the contrast. Hard to keep the eye lens clean given the short eye relief, and difficult to clean the tiny little piece of glass sunk in a hole. When I used them extensively I found it useful to wash my face and particularly my eyelids with soap and water just before going out to observe, it made a huge difference. For a while I even cut off my eyelashes to keep them clean during use. Interesting to me, of the ZAO I's the 4 mm was the most prized in the European market and garnered the highest price used.

[SteveC]

 

I often mention FC as a major aberration that I see in eyepieces and telescopes.  I am very sensitive to FC, because my eyes have virtually - perhaps no - accommodation for focus.  This means that if the eyepiece has FC I will see it.  And I read that the SM's have severe FC.  So I will not only see the FC, but chances are it will be a major distraction to me.  

 

Probably the only way that I would tolerate the FC in SM eyepieces, is if I acquire mounts that track, which I don't have now.   I don't think it would be cost effective to buy a decent tracking mount just so I can use SM's.

 

Mike

That's interesting, because I find pushing a scope a major distraction. All three of my mounts are tracking and I never considered that it was as a consequence of my eyepiece preference. I've always used tracking mounts while my non-tracking alt/az mounts languished in a closet. I don't think I'd be an ortho/supermono lover without a tracking mount.  Heck, I may not even be involved in the hobby since limited back flexibility limits my star hopping ability. 

 

Btw, I've never noticed,  or perhaps have never been bothered by FC.

[payner]

I see no astigmatism in the SM, either. I appreciate the link to the measured information provided.

 

I agree that washing one's face prior to observing with these eyepiece types helps a lot in maintaining the condition of the lens. I've never trimmed by eyelashes, but probably would help since mine are on the long side.

[Paul G]

I see no astigmatism in the SM, either. I appreciate the link to the measured information provided.

 

I agree that washing one's face prior to observing with these eyepiece types helps a lot in maintaining the condition of the lens. I've never trimmed by eyelashes, but probably would help since mine are on the long side.

It was funny, people noticed something was different when I trimmed mine, but nobody figured out what was different.

[Sarkikos]

  Trust me, the floater checkup I get with the 2.9mm ball is good enough for me. I suspect that I would use the 2.5mm XO  as rarely as i use the 2.9mm ball. Perhaps someday I'll run into someone with a 2.5mm at a star party and get a chance to evaluate it.

The 2.5 XO is fine for me, and I have a double boatload of eye floaters.  I just don't look at the Moon with it.  For me, a 2.5mm eyepiece on the Moon would be Floater Hades.  

 

Mike

Edited by Sarkikos, 16 January 2022 - 02:47 PM.

[Sarkikos]

Yep, XO2.5 is from time to time useful even in f/20. Here is a sketch made using XO5 and XO2.5

https://www.fzu.cz/~..._30/NGC7027.jpg

Yes, indeed.  You don't see eye floaters in Deep Space.  

 

Mike

Edited by Sarkikos, 16 January 2022 - 02:49 PM.

[Sarkikos]

I see no astigmatism in the SM, either. I appreciate the link to the measured information provided.

 

I agree that washing one's face prior to observing with these eyepiece types helps a lot in maintaining the condition of the lens. I've never trimmed by eyelashes, but probably would help since mine are on the long side.

The SM's would not have been good for Bambi. 

 

My eyelashes are naturally short, so I have that covered.

 

Mike

Edited by Sarkikos, 16 January 2022 - 02:52 PM.

[Sarkikos]

Jeff, thanks, that's it. Interesting that he measured no astigmatism, while Tom Back said the eyepieces reviewed by Sky & Telescope had "severe astigmatism" initially when he got them back, later changed it to "mild astigmatism."  As a primarily lunar/planetary observer I like to see the target in its context, like Jupiter and its moons, without having to focus back and forth to see one or the other. The SMs weren't my cup of tea.

 

For lunar observing these days I almost exclusively use Ethos, love that huge expanse of the lunar surface.

Field curvature and astigmatism are my two bugbears among eyepiece aberrations.  I don't like the other aberrations either, but FC and astigmatism are the two that really stand out, are the most obvious and most annoying.

 

Mike

Edited by Sarkikos, 16 January 2022 - 04:54 PM.

[Sarkikos]

That's interesting, because I find pushing a scope a major distraction. All three of my mounts are tracking and I never considered that it was as a consequence of my eyepiece preference. I've always used tracking mounts while my non-tracking alt/az mounts languished in a closet. I don't think I'd be an ortho/supermono lover without a tracking mount.  Heck, I may not even be involved in the hobby since limited back flexibility limits my star hopping ability. 

 

Btw, I've never noticed,  or perhaps have never been bothered by FC.

You don't need a nontracking scope to see FC.  Fast refractors - unless they are Petzvals or have a field flattener added - will have FC.   If you need to focus separately for outer field and center of field, there is FC.  If you only observe objects at center of field, maybe you won't notice.  But if you have a wide field eyepiece in a fast refractor that's not corrected for FC, and you glance around at stars in the outer field, I don't know how you couldn't notice, unless maybe your eyes have great accommodation for focus.

 

Mike

Edited by Sarkikos, 16 January 2022 - 08:20 PM.

[SteveC]

You don't need a nontracking scope to see FC.  Fast refractors - unless they are Petzvals or have a field flattener added - will have FC.   If you need to focus separately for outer field and center of field, there is FC.  If you only observer objects at center of field, maybe you won't notice.  But if you have a wide field eyepiece in a fast refractor that's not corrected for FC, and you glance around at stars in the outer field, I don't know how you couldn't notice, unless maybe your eyes have great accommodation for focus.

 

Mike

I don't think my eyes have a great accommodation for focus, I think it's my observing style. Even with a wide field I concentrate on the center. Certainly the % observed is greater in the wide field, and I just make minute adjustments with the hand controller when neccessary. I don't even think about FC at least to the point that it becomes bothersome.

[Sarkikos]

If your mount tracks, fc is no problem at all. It can be focused out anywhere in the fov. 

FC is still a problem if you want to see everything in focus at once, while looking around the entire field, without needing to refocus again and again.

 

Mike

[Jeff Morgan]

FC is still a problem if you want to see everything in focus at once, while looking around the entire field, without needing to refocus again and again.

 

Mike

I agree with you. Field curvature is a terrible sin - for a wide field eyepiece. Planets, not at all.

 

The largest planet is Jupiter, which runs about 45 arc seconds across. Even for a SMC used at high power, 45 seconds is a small percentage of the field diameter. There is no need (or purpose) to “look around the entire field”. What were you hoping to see in the background? M31?

 

A serious planetary observer has a mount with a drive, so the target is stationary. It is trivially easy to precisely focus such a small fraction of the field be it center, edge, or anywhere in between. Accommodation has nothing to do with it - because nothing is changing. 

 

A casual planetary observer would not have a driven mount, so yes drift would be a problem. Selecting a higher scatter wide field design with distortion and probably some astigmatism thrown in? You call that a Win?

 

The root problem is still not the eyepiece. It is the mount. Everything gets better when the earth stands still, including eyepiece choices. That is the Win.

 

Good day Sir.

[leonard]

The root problem is still not the eyepiece. It is the mount. Everything gets better when the earth stands still, including eyepiece choices. That is the Win.

 

 

                                  Exactly 

[Sarkikos]

I agree with you. Field curvature is a terrible sin - for a wide field eyepiece. Planets, not at all.

 

The largest planet is Jupiter, which runs about 45 arc seconds across. Even for a SMC used at high power, 45 seconds is a small percentage of the field diameter. There is no need (or purpose) to “look around the entire field”. What were you hoping to see in the background? M31?

 

A serious planetary observer has a mount with a drive, so the target is stationary. It is trivially easy to precisely focus such a small fraction of the field be it center, edge, or anywhere in between. Accommodation has nothing to do with it - because nothing is changing. 

 

A casual planetary observer would not have a driven mount, so yes drift would be a problem. Selecting a higher scatter wide field design with distortion and probably some astigmatism thrown in? You call that a Win?

 

The root problem is still not the eyepiece. It is the mount. Everything gets better when the earth stands still, including eyepiece choices. That is the Win.

 

Good day Sir.

I don't categorize serious and casual planet observers by their mounts.  Very good observations - and even sketches - are accomplished by planet observers without mounts that track.  Don't be an anti-mountist. 

 

If an eyepiece has a narrow usable AFOV, with outer field astigmatism and field curvature, those aberrations are definitely in the eyepiece, not in the mount.  I've never heard of a mount yet that had astigmatism or field curvature. 

 

Mike

Edited by Sarkikos, 17 January 2022 - 09:52 AM.

[Sarkikos]

The root problem is still not the eyepiece. It is the mount. Everything gets better when the earth stands still, including eyepiece choices. That is the Win.

 

 

                                  Exactly 

Don't encourage him. 

 

Mike

[payner]

I don't categorize serious and casual planet observers by their mounts.  Very good observations - and even sketches - are accomplished by planet observers without mounts that track.  Don't be an anti-mountist. 

 

If an eyepiece has a narrow usable AFOV, with outer field astigmatism and field curvature, those aberrations are definitely in the eyepiece, not in the mount.  I've never heard of a mount yet that had astigmatism or field curvature. 

 

Mike

There is no astigmatism in the TMB SM and FC is not seen through my telescopes (refractors of f/7 to f/8 and a f/10 corrected D-K). Understandably, most observers are not looking for the eyepiece that will show an improvement primarily when seeing is excellent and will be quite happy with Delos, XW, etc. However, when it is most important to a planetary observer, holding at bay that bit of scattered light will make the difference worthwhile to some (a few?).

[csrlice12]

And sometimes it's because eyepieces are easier to sneak past the CFO.....the 2.58XO is such a tiny thing...almost looks like a cheap plossl to the untrained eye.

Edited by csrlice12, 17 January 2022 - 11:37 AM.

[Sarkikos]

The best views of bright planets I have ever seen have been through pairs of Paradigms in a Burgess Binoviewer in my 10" f/4.7 non-tracking Dob.  Next best views have been through single XO's in my 10" f/4.7 non-tracking Dob.

 

Mike

Edited by Sarkikos, 17 January 2022 - 11:39 AM.

[Sarkikos]

And sometimes it's because eyepieces are easier to sneak past the CFO.....the 2.58XO is such a tiny thing...almost looks like a cheap plossl to the untrained eye.

And never tell them what you paid for it.  Just say, "I got it at a good price."

 

Mike

[leonard]

       Hello ,

 

Don't encourage him. 

 

Mike

Can’t we all just get along ?         

 

                            I like you Mike , have used  an alt/az mounted Newtonian for viewing planets . The best view I ever had

of a planet was by this method . But that was due to seeing and fine optics more than mount mechanics .

My best view of Mars was with a G11 equatorial Mount , it was a pleasure to view the planet over many minutes of

time without moving anything , and when needed just a touch of a button for correction . True it’s far more grunt and

fuss putting the g11 in place but it does have its rewards . An equatorial platform is an option .

An to Jeff’s point about the image staying centered in the eyepiece for me is the payoff for equatorial mounting of 

a planetary scope as one can use any kind of eyepiece from a ball eyepiece to a Back SMC or a 100 deg. eyepiece

and have the image always in the sweet spot , field curvature and astigmatism have no meaning then .

But that’s just about using an eyepiece in the most efficient way , any serious and dedicated planetary observer

will use good equipment honed to his or her personal style and ease of use and in the end will view just as much

detail as anyone else .

[leonard]

There is no astigmatism in the TMB SM and FC is not seen through my telescopes (refractors of f/7 to f/8 and a f/10 

 

              The Tom Back supermono. has no astigmatism in a properly constructed example .

 As for field curvature the design IIRC has some .

 Using an F7 refractor and a 5mm SMC I was not sure I could see it . It’s inconsequential at least for me .