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Choosing between Astro-tech AT80ED and AT92

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137 replies to this topic

#126 Erik Bakker

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Posted 02 April 2020 - 06:39 AM

IME, execution of a telescope design makes the most difference, along with glass types and the quality of it's melt and manufacture. Not all types of the same glass are created and melted equal. It generally gets better when the price goes up. And I agree that aperture and brightness differences due to that are to be considered alongside contrast, clarity and sharpness that are more related to quality of manufacture of a design, though good manufacturing quality together with good glass is ideal of course. 

 

That's why so many seeking great views in a portable scope end up with a small high quality apo. Over the decades, I ve seen and observed with many scopes, including small apo's of different design and quality. 

 

The joy coming from using a small high quality scope is real and a good antidode for aperture fever. My own scopes have been in the range of 55 to 406mm of aperture. My current most used scope is a very fine Nikon 82mm ED refactor made in Japan, unfortunately NLA. Could also have been a very fine 76, 78, 80, 89, 90, 92 or 94mm APO or MCT telescope, depending on what would have crossed my path. All great telescopes in that ballpark are a joy to use and own, just with slightly different accents.


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#127 25585

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Posted 02 April 2020 - 01:51 PM

Quality differences can even be seen in low power binoculars. Some cheaper good ones & disappointing expensive ones.

 

Admirak Ackbar, perhaps looking at other makes might interest you. While the AT92 seems to have its own uncontested slot, there are many 80mm ED makes around.

 

My TV-85 is expensive, but its tough. I have a S-W 80mm Equinox, also compact with a sliding dew shield. But the Vixen SD81S is what I would choose now. Its light enough for grab & go use & mounts, including a Porta 2, also Vixen. I have yet to read a bad report on a SD81 or the preceding ED81.


Edited by 25585, 02 April 2020 - 01:53 PM.

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#128 Reid W

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Posted 02 April 2020 - 03:13 PM

I've got an 81S, and it is a very good optic.  Sub 2" splits.  

 

Better than the ED80SF I had.  Higher mags, better polish, less scatter, better mechanicals (especially with a 2 speed unit).  My 90 knows it's been tested. 


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#129 AdmiralAckbar

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Posted 02 April 2020 - 09:37 PM

Thanks for the 81s suggestion. I had considered it, especially since I have an almost subconscious reverence for Vixen scopes, which I think is a lingering effect of seeing them advertised in astronomy magazines when I was a child.

 

But at 23" long, I don't think I would be able to take it as carry-on luggage when flying. If only one could disassemble it, ala Takahashi FC76...


Edited by AdmiralAckbar, 02 April 2020 - 09:42 PM.

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#130 25585

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Posted 03 April 2020 - 06:42 AM

A travel scope you might like if you can find one, is the Takahashi Sky 90. The 2nd version is best as the first had some issues with collimation I believe, but it's fluoride, lightweight and short. They pop up on Classifieds from time to time.   


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#131 jprideaux

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Posted 03 April 2020 - 09:26 PM

I do have to say that the moon looks nice with my AT92 with my ES 5.5 (100 degree) 2” eyepiece ( at 92x ). In a couple days I should be receiving a 2” 3x focal-extender which I will try (before the diagonal) and then use my WO binoviewer with 20 mm eyepieces on the moon. Hopefully that will be nice (at 76x).

I do have one 8-24mm Baader “click” zoom eyepiece. Maybe I’ll get a second (and a 2x focal extender)... once you start to get all these extra items for your scope, the initial cost starts to not matter so much. With almost any of these scopes, there are lots of other things you need to make the scope more useful for various things....

I personally do like a good quality small APO refractor for many things. But, yes, for planets, (or really dim things) you would want a bigger scope with more focal length (and aperture). Of course, the AT92 could be fine for larger dim stuff with Astro-photography.

Edited by jprideaux, 03 April 2020 - 09:28 PM.

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#132 gwlee

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Posted 04 April 2020 - 02:46 PM

The post you are quoting was deleted. But since you quickly responded to it before it disappeared you can see I specifically said that it was the contrast that was dramatically in favor of the Stowaway over the AT72ED2. If I had stopped my Stowaway down to 72mm (which I have done before) to even things up, still no contest. At 60mm the Stowaway still stomps the AT72ED2. Since the AT72ED2 uses fpl-53 glass I was surprised there was such a contrast difference. The Stellarvue 80 Access using fcd100 glass however has contrast that approaches that of Stowaway falling just a bit short, but still easily bettering the contrast of the AT72ED2 for some reason. SameTak 1.25 prism diagonal used, same eyepieces. 

Keep in mind that when you mask your Stowaway down to 72mm and compare it to your AT72ED2, are comparing a 72mm f8.5 scope to a 72mm f6 scope. The f6 scope has much more field curvature because field curvature is primarily a function of focal length (432mm vs 612mm). 

 

The short focal length of the  AT72ED2 was a deliberate design trade off to obtain a wider field of view and more compact scope dimensions at the expense of field curvature. The f5.5 AT92 makes the same trade off for the same reasons. In neither case can field curvature be considered a quality defect, but it’s one of the reasons I bought the Stowaway instead of the AT92.

 

To see the quality differences solely attributable to the differences between a good quality telescope and a sensibly perfect telescope of the same aperture size requires keeping the focal lengths the same too. 


Edited by gwlee, 04 April 2020 - 03:19 PM.

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#133 Moondust

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Posted 04 April 2020 - 03:25 PM

Keep in mind that when you mask your Stowaway down to 72mm and compare it to your AT72ED2, are comparing a 72mm f8.5 scope to a 72mm f6 scope. The f6 scope has much more field curvature because field curvature is primarily a function of focal length (432mm vs 612mm). 

 

The short focal length of the  AT72ED2 was a deliberate design trade off to obtain a wider field of view and more compact scope dimensions at the expense of field curvature. The f5.5 AT92 makes the same trade off for the same reasons. In neither case can field curvature be considered a quality defect, but it’s one of the reasons I bought the Stowaway instead of the AT92.

 

To see the quality differences solely attributable to the differences between a good quality telescope and a sensibly perfect telescope of the same size requires keeping the focal lengths the same too. 

I am well aware that stopping down the Stowaway to 72mm makes it an f/8.5. Once again I am comparing the contrast between two scopes (either stopped or non stopped) not field curvature. Though it is a very sharp optic the contrast difference is striking compared to either my Stowaway or Stellarvue 80mm Access even though it (AT72ED2 ) uses fpl-53 glass. As far as the OP's original question between the two scopes in question, this thread has gone on far too long with nothing settled. My advice, just get one or the other and enjoy the thing. Better yet get both. Then get back to us with some observation reports. There is no bad decision here. 


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#134 gwlee

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Posted 04 April 2020 - 05:50 PM

I am well aware that stopping down the Stowaway to 72mm makes it an f/8.5. Once again I am comparing the contrast between two scopes (either stopped or non stopped) not field curvature. 

What is contrast? How does field curvature effect focus? How does focus effect contrast? 


Edited by gwlee, 04 April 2020 - 05:53 PM.


#135 Auburn80

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Posted 04 April 2020 - 05:52 PM

I am well aware that stopping down the Stowaway to 72mm makes it an f/8.5. Once again I am comparing the contrast between two scopes (either stopped or non stopped) not field curvature. Though it is a very sharp optic the contrast difference is striking compared to either my Stowaway or Stellarvue 80mm Access even though it (AT72ED2 ) uses fpl-53 glass. As far as the OP's original question between the two scopes in question, this thread has gone on far too long with nothing settled. My advice, just get one or the other and enjoy the thing. Better yet get both. Then get back to us with some observation reports. There is no bad decision here.


IMHO, getting both and choosing based on direct comparison would be quite workable; given that one is so much less expensive.

#136 AdmiralAckbar

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Posted 04 April 2020 - 09:42 PM

As far as the OP's original question between the two scopes in question, this thread has gone on far too long with nothing settled. My advice, just get one or the other and enjoy the thing. Better yet get both. Then get back to us with some observation reports. There is no bad decision here. 

The OP created this thread as a way of eliciting perspectives that might help in making a decision. I have found it quite useful in that regard, do not feel any rush to settle, and feel grateful to all who have contributed.

 

With that said, I agree that there is sufficient information in this thread to help guide my decision.

 

I also admit that I find the confrontational spirit of some of the posts (which I also slipped into, to my discredit) tiring and uninspiring. So I will take this opportunity to thank everyone once again for sharing their perspectives, and then take my leave from further discussion.

 

My best,

AA


Edited by AdmiralAckbar, 04 April 2020 - 11:22 PM.

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#137 Phil Cowell

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Posted 06 April 2020 - 08:51 AM

Having all three, AT80, AT92 and AT102. If you can afford it the AT92 is a superb all round scope. No false color, fast so if you get into imaging a plus. Great travel scope. 

The OP created this thread as a way of eliciting perspectives that might help in making a decision. I have found it quite useful in that regard, do not feel any rush to settle, and feel grateful to all who have contributed.

 

With that said, I agree that there is sufficient information in this thread to help guide my decision.

 

I also admit that I find the confrontational spirit of some of the posts (which I also slipped into, to my discredit) tiring and uninspiring. So I will take this opportunity to thank everyone once again for sharing their perspectives, and then take my leave from further discussion.

 

My best,

AA


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#138 Erik Bakker

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Posted 07 April 2020 - 06:18 AM

Having either of these will always beat having none wink.gif


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