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DPAC Test - Zhumell 10" F4.9

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#1 Jeff B

Jeff B

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Posted 24 January 2021 - 06:12 PM

A friend an club member just took delivery of this brand new OTA.  He had no base for it so I asked if I could live with it for a bit and test it in DPAC.  He readily agreed.

 

I have to say I'm impressed with it as a package.  It's well put together with a light weigh tube that's reinforced on the ends, with a good focuser, nice 8x50 RA finder, easy to adjust primary and secondary holders (and they seem to keep their adjustments too.) and the primary holder has a nice, center mounted, impingement cooling fan. The focuser center axis was precisely aligned with the center of the tube too.  The offset secondary was well centered as well, requiring tweaking of just one adjustment screw to put the laser beam in the middle of the center spot.  Similarly, just a modest tweak of one of the push/pull screw sets was needed to put the barlowed shadow of the center spot over the laser aperture.

 

And then it went into DPAC.

 

Jeff

Attached Thumbnails

  • Z10 in DPAC.jpg

Edited by Jeff B, 24 January 2021 - 06:35 PM.

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#2 Jeff B

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Posted 24 January 2021 - 06:31 PM

Here are the results.

 

Overall a very good result, especially for the money.  The overall system figure is very good, with a touch of undercorrection but an excellent edge and only mild zoning.  Now it does have a moderate amount of  primary roughness which, IME, will manifest itself as a small loss in contrast on subtle low contrast features such as Jupiter's cloud belts.  However, that may only be noticed at high power, with excellent seeing by experienced observers and/or in direct comparisons with a system which is very smooth.

 

I also did not see any signs of astigmatism when sweeping through to both sides of focus (it would be seen as a "clocking" of the DPAC bars).

 

Excellent value here with this sample.

 

Jeff

Attached Thumbnails

  • Z10 DPAC, 133LPI, Inside, Null, Outside, B.jpg

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#3 Jon Isaacs

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Posted 25 January 2021 - 06:21 AM

Jeff:

 

Thank you for doing the test and posting the results. 

 

It looks good enough, I want to go out and buy one.. I probably would if I hadn't owned the 2002 version for the past 18 years :)

 

Jon


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#4 Jeff B

Jeff B

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Posted 27 January 2021 - 11:59 AM

Ok, by popular demand, a comparison of this system's image at focus with that of another 10" (F7) system of excellent quality.  This helps to put the surface roughness of the Z10 system into perspective. The F7's primary was recently touched up by CZ with his rouge polishing.  It started out a very good system to begin with as you can see in the attached "before" image on the left, but was smooothed by Carl.  I have encouraged the owner to just try the scope out first before deciding on whether or not to have the Z10 primary similarly smooothed out.   It would also be interesting to compare the Z10 to my 10" F7...but that won't happen anytime soon really.

 

Jeff

Attached Thumbnails

  • Focus comparison with 10 F7 CZ tune up.jpg

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