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Do CATs have Premium Optics

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258 replies to this topic

#251 gnowellsct

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Posted 10 June 2018 - 01:05 PM

well I mean, you know, consistently good.  Consistently bad is pretty easy.  GN


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#252 gnowellsct

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Posted 10 June 2018 - 01:08 PM

IThey are great at what they are intended to do - provide a lot of aperture in a small package.  In the refractor world, premium scopes have optics from companies such as TEC, Tak, LZOS, LOMO, and a few others.  

Actually Scott some of them are pretty bad.  Even the premiums.  And some you would expect not to be so great, actually do OK.  Who is *consistent*?  Good question.  Not enough data.  

 

I recommend the C14 Edge_HD myself but NOT until the grease outgassing problem has been solved.



#253 Scott Beith

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Posted 10 June 2018 - 03:49 PM

Actually Scott some of them are pretty bad.  Even the premiums.  And some you would expect not to be so great, actually do OK.  Who is *consistent*?  Good question.  Not enough data.  

 

I recommend the C14 Edge_HD myself but NOT until the grease outgassing problem has been solved.

I have 10 years until retirement.  They should solve it by then.  wink.gif



#254 Jeff B

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Posted 10 June 2018 - 08:52 PM

I have 10 years until retirement.  They should solve it by then.  wink.gif

Well I certainly hope so as my greasy hair and outgassing are getting worse with age.


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#255 gnowellsct

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Posted 13 June 2018 - 10:24 AM

Well I certainly hope so as my greasy hair and outgassing are getting worse with age.

Scott, like myself, would be LUCKY to have hair that was greasy.


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#256 Whichwayisnorth

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Posted 13 June 2018 - 11:15 AM

show me a mass produced CAT with a Strehl of 0.96 that costs less than $10K

Jason Ware has a Meade 14" F/8 LX850 OTA with a Strehl of .98 and mine was .97.  I have sold it to Joe Sardina who is the owner of Nightskies Network.  I don't know if the still has it.

 

Considering that at the time very few had been made the odds seem rather good.


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#257 Whichwayisnorth

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Posted 13 June 2018 - 11:21 AM

I skipped a couple of pages in this thread.  Has anyone mentioned the Vixen VMC200 or 260L?  what about the VC200L which is somewhat like the EdgeHD in that it has corrective optics in the baffle tube.

 

Without any evidence to support it I would believe that Japanese Optics in small quantities would generally be superior to mass produced Chinese optics.

 

The prices are reasonable too.



#258 gnowellsct

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Posted 13 June 2018 - 12:02 PM

I skipped a couple of pages in this thread.  Has anyone mentioned the Vixen VMC200 or 260L?  what about the VC200L which is somewhat like the EdgeHD in that it has corrective optics in the baffle tube.

 

Without any evidence to support it I would believe that Japanese Optics in small quantities would generally be superior to mass produced Chinese optics.

 

The prices are reasonable too.

I tend to agree with you, and have based my purchasing decisions on the same idea, but it doesn't always work out that way.  The current generation of Synta SCTs are probably about as good as they ever have been.  

 

The models you mention have not "taken off" in the U.S.  Perhaps people prefer the Tak Mewlon if they're into this design at all. 

 

There are 4  Vixen tests on the Airylab web site  and if you look for the Strehls (lower left, just outside the box that shows the graph of the tests) for each wavelength they're not as favorable as those of us who have a favorable view of Vixen would like them to be.   What to make of I can't say, perhaps those of us who like the 81s are deeply mistaken, or there was a  bad unit, or Airylab doesn't know how to test.   It is to be remarked that of the two Mewlons 250s one is good, one not so good.

 

 

Greg N



#259 macdonjh

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Posted 13 June 2018 - 12:57 PM

I took a vacation from this thread and missed a lot.  Some comments that are now random:

 

I enjoyed having a Crayford focuser on my C11.  It was easier finding sharp focus.  My original thought was removing the slop in the threads of the Celestron SCT focus mechanism from the equation made all the difference.  Now I'll add focusing an f/10 light cone, rather than an f/2 light cone to the analysis.

 

I can't remember if this got settled: I think depth of focus is dependent only on focal ratio since it's about how far on either side of perfect focus the instrument can be and still be perceived by an observer to be in perfect focus.  The light cone of an f/12 instrument is pretty shallow, so even if the focuser is 5mm away from perfect focus, the image may seem to be in focus to the observer.  Contrast that with the steep light cone of an f/4 scope.  That same 5mm away from perfect focus may be far enough out to make the image blurry to the observer.

 

Both Maksutovs and Schmidts are catadioptric (CAT) telescopes.

 

Magnification for me is always limited by seeing.  If seeing is poor, I will either put my scope away or use low magnification.  Where I observe I get a few nights a year when 300x is worth using.  There have been two nights in all the time I've observed that I had wished I could use more than 560x.  That was with my Driveway Scope (8"), but the shortest focal length eye piece I had was 7.4mm.

 

I don't chase the seeing when I focus.  If seeing is variable, I'll focus on a star, then move to the planet or deep sky object I am interested in.  I find it simpler to focus on a wavering star image.  Then I can be certain enough that my focus is good that I can be patient and wait for those fleeting moments of steady seeing and not find myself wasting those moments fiddling with my focuser.  




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