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RocketScientist
super member


Reged: 08/28/08

Loc: California (East Bay area)
Re: Zhumell Z10 10" Dobsonian Review new [Re: Seattle Brian]
      #5190961 - 04/26/12 12:51 AM

tinrinnie,

So tell us about your experiences with your Z10! How is it working out for you?

Cathy


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Angie
newbie


Reged: 10/23/12

Loc: SoCal
Re: Zhumell Z10 10" Dobsonian Review new [Re: RocketScientist]
      #5990412 - 07/25/13 10:45 PM

I just found this thread, and the superb review by Cathy James of the Z10....
Hi Cathy,
I just happened across your excellent 1/19/11 review of your Z10. Wow, having bought the identical telescope last summer in 2012 (under the name Apertura,and called the A10),
every word of your review reflects my own experiences exactly.
Thanks for writing it.
I had the same sinking feeling you describe so well when looking through a Cheshire! What a mess of non-concentric confusion. No one in the local astronomy club could figure it out either, and these guys are all into telescope making and optics. I gave up trying to sort it out, concluding that the secondary may not be set precisely in the center of the tube, or maybe it is not in a precise 90 degree relationship to the axis of the focuser. I wasn't sure if the focuser was even set at a 90 degree angle to the tube's geometric axis. Then I thought, well maybe the geometric axis is different from the optical axis of the primary...which would make the problem even more complicated.
My brain shorted out at that point, and I just did the 'collimation' with the laser included with the scope, according to the simplistic instructions included in the very sketchy user's manual, and some comments made by the people who sold me the telescope when I called them for help.
Now, despite this ongoing nonconcentricity of the profiles of the mirrors as seen through the Cheshire, when I just collimate with the simple red dot procedure, and get it really precise, the telescope performs quite well optically, at least on axis, though I wonder if it could be even better if the job were done 'right' by eliminating subtle angular distortions in the mechanical alignments of the telescope tube that must surely result in off-axis optical distortions of the light cone, such that while the red dot might well be lined up, the surrounding light cones are somewhat askew, leading to coma, astigmatism etc just beyond the center of the FOV. As an anecdotal example, last winter I could see the E and F stars in the Trapezium on nights when other, bigger and more expensive telescopes failed. That seems so unlikely if the wonky alignments of the tube components really impact performance significantly, don't you think?
So I'm wondering if you have learned any more about this issue of collimation, how important is it, and why does the Cheshire differ from the laser collimator and which one should we believe.
Thanks...and clear skies to you
Angie
Santa Barbara


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AstroTatDad
Pooh-Bah
*****

Reged: 04/22/13

Loc: Los Angeles - San Diego
Re: Zhumell Z10 10" Dobsonian Review new [Re: Angie]
      #5990633 - 07/26/13 01:23 AM

Quote:

I just found this thread, and the superb review by Cathy James of the Z10....
Hi Cathy,
I just happened across your excellent 1/19/11 review of your Z10. Wow, having bought the identical telescope last summer in 2012 (under the name Apertura,and called the A10),
every word of your review reflects my own experiences exactly.
Thanks for writing it.
I had the same sinking feeling you describe so well when looking through a Cheshire! What a mess of non-concentric confusion. No one in the local astronomy club could figure it out either, and these guys are all into telescope making and optics. I gave up trying to sort it out, concluding that the secondary may not be set precisely in the center of the tube, or maybe it is not in a precise 90 degree relationship to the axis of the focuser. I wasn't sure if the focuser was even set at a 90 degree angle to the tube's geometric axis. Then I thought, well maybe the geometric axis is different from the optical axis of the primary...which would make the problem even more complicated.
My brain shorted out at that point, and I just did the 'collimation' with the laser included with the scope, according to the simplistic instructions included in the very sketchy user's manual, and some comments made by the people who sold me the telescope when I called them for help.
Now, despite this ongoing nonconcentricity of the profiles of the mirrors as seen through the Cheshire, when I just collimate with the simple red dot procedure, and get it really precise, the telescope performs quite well optically, at least on axis, though I wonder if it could be even better if the job were done 'right' by eliminating subtle angular distortions in the mechanical alignments of the telescope tube that must surely result in off-axis optical distortions of the light cone, such that while the red dot might well be lined up, the surrounding light cones are somewhat askew, leading to coma, astigmatism etc just beyond the center of the FOV. As an anecdotal example, last winter I could see the E and F stars in the Trapezium on nights when other, bigger and more expensive telescopes failed. That seems so unlikely if the wonky alignments of the tube components really impact performance significantly, don't you think?
So I'm wondering if you have learned any more about this issue of collimation, how important is it, and why does the Cheshire differ from the laser collimator and which one should we believe.
Thanks...and clear skies to you
Angie
Santa Barbara




Hi Angie,
I have the Z8 and like it very much, I have been using the "laser/collimater" that came supplied with the Z8. I haven't upgraded yet, it seems to do the job for me. I did collimate the laser and that helped out a lot, also upgrading to stiffer springs on the primary mirror was another plus.

If a Z12 or AD12 would fit in my car I would definitely get one of them.

Clear Skies.


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