Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Collimation question

  • Please log in to reply
1 reply to this topic

#1 dcm_guitar

dcm_guitar

    Mariner 2

  • *****
  • topic starter
  • Posts: 277
  • Joined: 08 Sep 2020

Posted 15 September 2021 - 12:58 PM

I'm getting more facility using a long focal length reflector.....

 

I did my first collimation recently.  I did't use an eyepiece.  Instead, I used images to check the "donut hole" in the center of unfocused stars.  I unfocused an image, and then zoomed in to the center of the image to see the star halos.  I got what looks like a great result in the center.  However, when I look at the star halos around the edges, the collimation looks off.  The center looks great, but the edges look odd.

 

Is this a collimation issue or is this a camera tilt issue or is this a back focus issue?

 

For the record, I'm using an EdgeHD 9.25 at the native f/10.  The camera is an ASI 6200MM and the images are taken through a ZWO luminance filter (which I know isn't the best).


Edited by dcm_guitar, 15 September 2021 - 12:59 PM.


#2 Madratter

Madratter

    Voyager 1

  • *****
  • Posts: 13,218
  • Joined: 14 Jan 2013

Posted 15 September 2021 - 02:29 PM

THE problem that so many around here have had using the camera for doing collimation is that they do it with the camera way too far out of focus. The test becomes much more sensitive as you get closer and closer to focus. And you can judge the collimation when close to focus by how evenly illuminated the arcs around the star are. I.e. as you get close to focus, if you are out of collimation, the one side of the star will look brighter.

 

So by all means start by being out of focus and the adjusting the donut hole. But once you get "somewhat close" (which is really probably not all that close) then switch to use which side of the star is brighter.

 

The star MUST be centered.


  • dswtan and dcm_guitar like this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics