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Frustration with some kind of abberation

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30 replies to this topic

#26 Starman1

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Posted 29 October 2020 - 09:02 AM

Agreed.  A curved spider is not compatible with a 4" secondary where collimation stability is concerned.



#27 jagg3d

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Posted 29 October 2020 - 04:59 PM

So I disassembled the scope after work yesterday. I had tightened the clips down pretty good. Took the mirror out of the cell and it is resting on three cork spacers half an inch diameter. Effectively they supported the middle of the mirror and helped act as the fulcrum for the clips to bend the mirror. I had double sided tape from installing the secondary so I used that and left the clips with about a mm play so if the mirror falls forward (doubtful) they would catch it.

 

How did it work? Last night I had the best view of Mars I've ever had. Atmosphere was great but the telescope performed really well. The northern Ice Cap was a sharp white dot and the features on the surface stood out.


Edited by jagg3d, 29 October 2020 - 04:59 PM.

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#28 wrnchhead

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Posted 29 October 2020 - 05:22 PM

Great result!

#29 MitchAlsup

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Posted 29 October 2020 - 06:04 PM

Agreed.  A curved spider is not compatible with a 4" secondary where collimation stability is concerned.

Also note the thickness of those vanes is diffracting a lot of light. In comparison, my 4-vanes supporting my 3.8" secondary are only 0.007,5" thick (twice the thickness of typing paper.)


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#30 wrnchhead

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Posted 29 October 2020 - 07:17 PM

By the way this thread is going to have me tearing my sky watcher down to the bare bones because I have never been too impressed with it compared to my Apertura 8” and my C8.
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#31 TiSaph

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Posted 03 November 2020 - 08:23 AM

Well, I shortened the cable sling, but unfortunately that didn't really improve the view.  I was really hoping the problem was the weight of the mirror resting on two posts.  Anything above 100X is fairly ugly, and Mars has zero contrast.  There's only really three things left it could be: the secondary mount, the secondary itself, or the primary itself.   I will re-mount the secondary again, adjusting the cotton batting and trying to get it looser in the holder.  If that doesn't work, I might send out the optics for testing ...


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