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Old 05-09-2013, 01:22 PM
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Lee
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Elongation in parts of image - troubleshooting advice requested....

I've noticed some elongation this week, when previously it wasn't there, and it only seems present in various parts of the sky.
I recently converted from a SBS/guide scope to OAG/lodestar - so the only difference is the OAG in the image train, and everything is threaded together. The OAG itself is in two parts, held by three compression screws though....
The image train is - moonlite focuser/MPCC/TSOAG9/Orion filter wheel/Atik 420.

My thoughts are there is some flex in the OAG at this joint, so I'm planning on pulling it all down and tightening up/collimating etc.

CCDInspector reported collimation is pretty good around 5" off or so, of course my trial expired before I could do some better measurements! Have just registered it, so tonight I may get some more data (expensive software!)....

Does anyone have any advice on this?
Tips to actually diagnose the issue??

The images are high in the NW, and high in the SE this week....

Thanks in advance...
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Old 05-09-2013, 11:02 PM
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h0ughy (David)
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wow that's unusual, almost like the optics are not lined up?
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Old 06-09-2013, 01:48 AM
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Joshua Bunn (Joshua)
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Yes, like mis-collimated a little. 5" for a collimation figure is quite large.

Josh
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Old 06-09-2013, 07:52 AM
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Colour is over-rated

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I pulled everything down, checked all the fittings in the image train, I couldn't find any significant tilt with feeler gauges/micrometers.
Then checked scope collimation with the Glatter laser.
The dot missed the primary centre by about 20mm, and the return dot on the base of the laser barely hit the base of the laser!
I suspect the collimation was off by so much that it confused ccdinspector, which reported it as tilt??

I know I didn't re-collimate after re-mounting the OTA last weekend....
Such a rookie mistake!
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Old 06-09-2013, 08:48 AM
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pvelez (Pete)
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It happens to us all Lee

Looking at your images, I'd suggest it was collimation

Pete
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Old 06-09-2013, 10:46 AM
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In my experience, ccdinspector will overlap tilt and collimation, one will effect the others figures. so its helpful to get either tilt or collimation sorted so you know for certain its right, then go from there on the other one. its an iterative process also as one will appear to effect the other slightly.

Josh
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Old 06-09-2013, 10:50 AM
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Colour is over-rated

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From memory ccdi reported 16%+ tilt, with the 'red' in the bottom left...
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Old 06-09-2013, 10:56 AM
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yes, 16% is a heap. But like i said, this could also be miscollimation creeping in. I would suggest to collimate the scope pretty will, then work on the tilt then go back to the collimation. What kind of focuser and autofocus routine do you use?

Josh
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Old 06-09-2013, 02:20 PM
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Colour is over-rated

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I've collimated with the laser last night, will takes some test images on the weekend if it clears....
Focuser is a moonlite with stepper motor, autofocus through SGPro (100 star HFR based).
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