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C5 spotting scope, any lemons?

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#1 Tom Stock

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Posted 10 October 2019 - 06:10 AM

I've read that most of the C5's are good, some great, but haven't heard of any particularly bad ones.

I picked up an open box C5 spotting scope on amazon for $350 and am hoping it wasn't a lemon returned for poor optics.

I figured it's worth the risk since amazon will accept a return should it be so-so where buying used from an individual you are typically stuck with your purchase.

 

Really wanted it for a travel scope and the soft case and tripod mounting hole are a plus.

 

I owned a classic C90 and was underwhelmed.. focus was awkward and planetary views soft. Hoping the  5 will be a lot better.


Edited by Tom Stock, 10 October 2019 - 06:16 AM.


#2 Sky Muse

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Posted 10 October 2019 - 07:50 AM

Schmidts(C5) and Maksutovs(C90) are reflectors, and therefore are able, or should be able, to be collimated.  Schmidts lose their collimation more frequently than Maksutovs, yet are the easiest of all reflectors, including Newtonians, to collimate.  Simply ensure that the C5 is collimated before a final determination, and hope for the best. 



#3 Chuck Hards

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Posted 10 October 2019 - 11:51 AM

I tested 3 orange-tube C5's and found all three lacking under DPAC, 133LPI Ronchi.  The two white-tube C5+ scopes I've owned tested better.  One is ~1/4 wave (system), the other a bit better.  About as good as it gets with SCT's.

 

I've never owned a C90 that I considered good enough to hang onto, went through 3 of those too.


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#4 Tom Stock

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Posted 10 October 2019 - 05:08 PM

Thanks,

Regarding the orange tubes are you referring to the classic orange fork mounted C5, or the modern metalic Orange C5?

#5 Chuck Hards

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Posted 10 October 2019 - 10:34 PM

Two were old, though I can't recall the years of manufacture, one was modern.  They weren't terrible; the older ones were American made and might have been a tad better than the modern one.  But these days I judge SCT's against my modern C6 (~2009) which shows about the best lines I've seen yet with an SCT.  



#6 Erik Bakker

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Posted 11 October 2019 - 06:25 AM

All (mass produced) scopes show sample variation. The best way to tell the quality of the optics in a specific C5 is to evaluate it under the stars. Check and if necessary adjust collimation first, then take it to 120x-150x and see how it performs. I have a very good C5, but it is still a mass produced scope with a large central obstruction. So set realistic expectations. I find it a very enjoyable scope though.



#7 Chuck Hards

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Posted 11 October 2019 - 08:46 AM

Erik, I am very familiar with the nuances of the compound telescope, I don't test uncollimated telescopes under DPAC, and the central obstruction size doesn't affect the Ronchi pattern.  Optics are either smooth and well-corrected, or they are not.   I also understand sample variation, but after using them for half a century, it's plainly obvious to me that the mass-produced SCT just isn't up to the same level optically as that of premium scopes.  Now, that's not necessarily a bad thing, as cost to the consumer would probably triple if each unit was individually hand-corrected to the same level as say, a Questar, for example (and even Questar has let a few howlers through, unfortunately).  At some point the manufacturer has to say "good enough" when trying to reach a price point.  By and large, many are close to the diffraction limit but most are not as good as their owners believe.




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