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

Software tools for collimating an EdgeHD (or any SCT)

  • Please log in to reply
1 reply to this topic

#1 t-ara-fan

t-ara-fan

    Ranger 4

  • -----
  • topic starter
  • Posts: 359
  • Joined: 20 Sep 2017

Posted 23 April 2019 - 01:33 AM

I have been collimating my EdgeHD8 regularly, as I switch back and forth between the normal secondary and Hyperstar.  I just eyeball the donut of an unfocused star.

 

Is there a better way?  I use SGP and SharpCap. I have a Hotech Hyperstar Collimator, which gets me very close but I don't think it is perfect, I think need a star test to get perfection.

 

Some things I am looking at:

  • CCDInspector looks really good, but I use SGP, and I think CCDInspector needs CCDSoft of MaximDL (?)
  • MetaGuide
  • Get a TriBahtinov mask, one that is hinged to fit around my Hyperstar camera.
  • Some simple software to tell me if the hole in the donut is perfectly centered.

Comments on what works best would be appreciated. The star moves off center when adjusting collimation, so software that can control the mount would be sweet, to keep that star centered.



#2 jdupton

jdupton

    Surveyor 1

  • *****
  • Posts: 1553
  • Joined: 21 Nov 2010
  • Loc: Central Texas, USA

Posted 23 April 2019 - 10:46 AM

t-ara-fan,

 

   I use MetaGuide for critical collimation of my two SCTs (old Meade 10" & Celestron 11" EdgeHD).

 

   I don't use any special collimation tools. My own process goes something like this:

  • Eyeball initial collimation by simply looking down the tube (from both front and back) and getting the "Hall of Mirrors" view reasonably close. Unless I have done major work on the OTA like removing the corrector or such, this step is rarely even required as it will be close enough to start.
     
  • Put in a Webcam or Planetary imaging camera, connect MetaGuide, and center a star high overhead. I choose a medium bright star of 2nd to 3rd magnitude. I use exposure times of about 0.1 second.
     
  • In the beginning, I leave the star unfocused so that it takes up about 1/8 to 1/4 of the field of view. 
     
  • I adjust the collimation screws and watch the star until the donut appears centered. I then repeatedly focus to make the donut smaller and smaller while making further refining collimation adjustments until the star is close enough to focus that the now centered donut appearance disappears. Recentering of the star is required as you tweak the collimation screws.
     
  • At that point, I add a Barlow (actually my Televue 2x PowerMate) to the image train and focus the camera until I can see the Airy Disk reasonably clearly in the MetaGuide close-up window. I then set MetaGuide to start doing a running average of 10 to 15 images to smooth out seeing and give a better image of the Airy Disk. MetaGuide will place markers around the Airy Disk indicating the directions of any asymmetry. I continue tweaking the collimation screws until I am unable to make it any cleaner given the seeing conditions. At that point, I am usually done.
     
  • On nights of excellent seeing, if I want to dial it in even better, I will stack another Barlow onto the PowerMate and do one last round of minuscule tweaks to the collimation as in the previous step.

   The first time I did a very critical collimation like this to my old 10" Meade, I was astounded at all I had been missing in prior years of use. I decided to keep the scope for visual as it was no longer a "meh" scope when properly tuned up.

 

 

John


  • mike8888, rave3c0, t-ara-fan and 1 other 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