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Old 13-05-2024, 07:49 PM
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mldee (Mike)
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Join Date: Aug 2008
Location: Near Warwick, Qld, Australia
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Advice on RC8 star collimation

Finally, clear nights and temps still above zero!
Put the OCAL-collimated RC8 with imaging train on the AM5 with a 183mm binned 4 screwed onto the OAG housing.

First pics before any adjustments looked promising, although some donut variation across the image.

I have two questions:

1 - What is causing the variations in roundness
2- Which screws to tweak to improve roundness: Primary, secondary or image train adjusters?

Pic shows setup and initial image before any adjustments.
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Old 18-05-2024, 10:19 PM
MarkInSpace (Mark)
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Join Date: Jul 2020
Location: Melbourne
Posts: 249
RC8 collimation

Hi Mike,
My approach may be naive, but it seems to work for me:
I approach RC collimation as 2 tasks - out of focus (OOF) roundness, and
centering the central OOF point.

I first Center the secondary using my eyes.
The the OOF roundness is adjusted with the collimation screws on the body of the telescope. Use a circle in your display to help get roundness correct.
Next adjust the secondary to Center in the image. When it gets close, you will see most of the OOF images are centered.
Here’s the type of resolution I am getting with my RC-8 carbon.

Last edited by MarkInSpace; 18-05-2024 at 10:24 PM. Reason: Added link
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