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Hyperstar off-axis color aberration

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#1 Clouzot

Clouzot

    Mariner 2

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Posted 22 October 2020 - 03:36 PM

Hi all,

 

When shooting last time with my C9 (non EdgeHD), Hyperstar v4 and Altair 294c, I noticed once again something that has been bugging me since I acquired the Hyperstar from Starizona: no, it's not that I'm badly undersampled (I know I am, blocky stars and all), but

  1. stars have a sligthly elongated shape (not totally equivalent when you look at different corners)
  2. color channels seem to be focused at different positions in the field, in this order going from the center: green, blue, red

Here's an example of a 30s bin1 sub, for which I stretched the levels a bit and set max saturation in order to see that color aberration: I isolated the four corner of the image, Pixinsight-style (I don't have a PI license so it's done by hand, sorry for the bad editing)

 

color_upperleft.jpg color_upperright.jpg

color_bottomleft.jpg color_bottomright.jpg

 

I'm by no means experienced in AP, but it looks like I don't have the spacing right between the Hyperstar and the sensor. I'm a bit surprised because Dean asked me about my exact camera model when I ordered, so that they could send me the right adapter with the correct spacing.

 

I'm also surprised because I'd have expected green to be between blue and red, not outside.

 

Does someone know what is the problem here? Spacing (if so, should I add or... remove, and how much? I'd prefer the former, due to the Hyperstar adapter being a one-piece tube)? Normal aberration with Hyperstars? Collimation issue? Or maybe all of the above, or something else...

 

Thanks in advance!




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