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Shocker: $7.60 VITE 23mm Eyepiece beats others for detail

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#51 SeattleScott

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Posted 31 May 2020 - 08:46 AM

Well he did the fast scope test for edge correction with his F6. So a 1900mm Mak would be a good higher power test for contrast and n the Moon. Yeah it still isn’t really high power, but it isn’t really a high power eyepiece. It should be interesting to see if F15 fixes the edge performance. Sure a C11 or 7” Mak would be better, but one has to go with what they got.

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#52 Hesiod

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Posted 31 May 2020 - 01:00 PM

At 80X? A test, sure, but a very forgiving one.

On the other hand, splitting Polaris or Rigel would tell something about the amount of light scattered by each eyepiece, as the Pleiades' associated nebulae



#53 RichA

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Posted 31 May 2020 - 02:40 PM

The Moon at 80x is no exactly a challenging test; I'd rather try them on very bright stars, maybe wide, uneven double stars, or "peculiar" targets such as the Pleiades.

That won't tell you much except how much edge aberrations and distortion they have.



#54 RichA

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Posted 31 May 2020 - 02:44 PM

Well he did the fast scope test for edge correction with his F6. So a 1900mm Mak would be a good higher power test for contrast and n the Moon. Yeah it still isn’t really high power, but it isn’t really a high power eyepiece. It should be interesting to see if F15 fixes the edge performance. Sure a C11 or 7” Mak would be better, but one has to go with what they got.

Scott

I've got an 8 inch SCT, but I'm not sure why going with larger and larger scopes will accomplish much.  For one thing, you become more dependent on seeing conditions than eyepiece quality most of the time.  Testing should really be done when you know the scope's aperture won't be too large for the sky conditions to support.  A 5" can be used more often at its resolution limit than 7 or 11 inch scope.


Edited by RichA, 31 May 2020 - 03:27 PM.


#55 SeattleScott

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Posted 31 May 2020 - 09:37 PM

My point was more the focal length than aperture. The 5” Mak has about the same FL as an 8” SCT so either would be about the same.

Scott

#56 RichA

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Posted 31 May 2020 - 10:53 PM

My point was more the focal length than aperture. The 5” Mak has about the same FL as an 8” SCT so either would be about the same.

Scott

I think clearly that increased focal-ratio will have an impact on how an eyepiece performs, at the edges anyway, but increase focal length, I'm not sure it will impact the eyepiece at all.  An eyepiece at 500mm should perform the same at 2000mm, as long as focal ratio stays the same.  I don't know how aperture (beyond aperture being impacted by seeing conditions) will effect an eyepiece's performance.  If you vary the exit pupil, it's as likely unless you have perfect vision, or vision corrected to perfect, your eye will have some impact on performance of the system.



#57 Hesiod

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Posted 01 June 2020 - 01:17 AM

That won't tell you much except how much edge aberrations and distortion they have.

No, you'll see also how the light is scattered and could underline also possible aberrations across the whole field.

#58 epee

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Posted 02 June 2020 - 08:04 AM

I received a set along with a Meade HD60 25mm a few days ago and finally had a chance to look at something beside the clouds last night.

This was not an exhaustive test, and is honestly more of my own impressions.The subject was the Moon through an f/10 and f/6 achro 102mm refractors

The Meade HD25 was great; comfortable, crisp, good contrast and little to no scatter.

The Svbony 23mm wasn't bad at all; again comfortable, crisp, contrast was good but not up to the Meade, and there seemed to be some light scatter.

The Svbony 10mm was still worth the bucks; tighter eye relief but still usable with glasses, focus seems a tad critical, contrast was decent but not great.

The Svbony 4mm is definitely the weak sister; eye relief is tight, focus was extremely critical, and the view was very soft, I found edge of field distortion very evident as the center and edges could not be focused that the same time. Much of this is likely due to the short focal length.

 

The 4mm might be the subject of optical experimentation in the coming days....


Edited by epee, 02 June 2020 - 08:34 AM.

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#59 howardcano

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Posted 02 June 2020 - 10:48 AM

The subject was the Moon through an f/10 and f/6 achro 102mm refractors. The Meade HD25 was great; comfortable, crisp, good contrast and little to no scatter...

 

The Svbony 4mm is definitely the weak sister; eye relief is tight, focus was extremely critical, and the view was very soft, I found edge of field distortion very evident as the center and edges could not be focused that the same time. Much of this is likely due to the short focal length.

The 25mm HD60/XCel LX is a great buy!

 

And, I'd be surprised if any 4mm eyepiece would have looked sharp in those scopes.



#60 epee

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Posted 02 June 2020 - 11:02 AM

The 25mm HD60/XCel LX is a great buy!

 

And, I'd be surprised if any 4mm eyepiece would have looked sharp in those scopes.

Likewise. As a matter of fact, I don't think I could have given a 4mm a proper run for sharpness in any scope I own, not under my typical seeing conditions.

 

Of course that didn't change the fact that eye relief was uncomfortably tight for an eyeglasses wearer, the focus was very critical, and the entire field didn't focus at the same place.grin.gif

 

Someone in this thread mentioned that it might be possible to remove ath Smyth lens and render it into an 8mm (or such). I might play around with that as it would be FAR more useful to me in a longer focal length.


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#61 SeattleScott

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Posted 02 June 2020 - 01:03 PM

I think clearly that increased focal-ratio will have an impact on how an eyepiece performs, at the edges anyway, but increase focal length, I'm not sure it will impact the eyepiece at all. An eyepiece at 500mm should perform the same at 2000mm, as long as focal ratio stays the same. I don't know how aperture (beyond aperture being impacted by seeing conditions) will effect an eyepiece's performance. If you vary the exit pupil, it's as likely unless you have perfect vision, or vision corrected to perfect, your eye will have some impact on performance of the system.

A higher F ratio will improve edge performance. But you already indicated the edge performance was worse than the others so then the issue becomes contrast in the center of the field. For a lunar shootout evaluating contrast, you want enough magnification to see the details. And with 23-26mm eyepieces you need some long focal length to get much magnification. Otherwise you might as well be test driving a car through a school zone. Gonna be hard to tell much difference between a Honda Fit or a Ford Shelby Mustang with a 20mph speed limit. Just like it could be hard to tell a difference between a SVBONY or a Brandon at 20x magnification. So either the SCT or the Mak would work about as well since they have similar focal length.

Scott


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