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

About to get My First SCT..Can I use a Glatter Collimator to Collimate it?

  • Please log in to reply
11 replies to this topic

#1 bluenote

bluenote

    Explorer 1

  • *****
  • topic starter
  • Posts: 75
  • Joined: 25 Nov 2012
  • Loc: San Francisco Bay Area

Posted 05 August 2021 - 08:38 PM

Just about to get my first SCT, a Celestron C11 HD.  Never collimated an SCT before...So, can I use my Howie Glatter Collimator with Tu Blug to collimate it?



#2 barbarosa

barbarosa

    Gemini

  • *****
  • Posts: 3,169
  • Joined: 11 Apr 2010
  • Loc: 139 miles W of the Awahnee Hotel

Posted 05 August 2021 - 08:47 PM

Not perhaps in the way you might expect. See this about using i with an SCT.


  • bluenote likes this

#3 bluenote

bluenote

    Explorer 1

  • *****
  • topic starter
  • Posts: 75
  • Joined: 25 Nov 2012
  • Loc: San Francisco Bay Area

Posted 05 August 2021 - 09:33 PM

Thanks Barbarosa....Gotta say that's a hell of a lot of work!



#4 macdonjh

macdonjh

    Fly Me to the Moon

  • *****
  • Posts: 6,763
  • Joined: 06 Mar 2006

Posted 05 August 2021 - 09:39 PM

I found lasers to be not particularly helpful with SCTs.  They aren't that hard to collimate, anyway, since only one mirror is involved.  There are dozens of threads in the Cats and Casses forum here about collimating an SCT.  My particular favorite for daytime collimation is the "concentric circles" method where you look into the front of the scope from ten or fifteen feet away and adjust the secondary mirror until all the circles you see are concentric.  That simple method gets you amazingly close to good collimation.  From there you can collimate incrementally using a real star: just check the seeing each night you set up.  If the seeing is better than the last time, tweak collimation.  If it's not, leave your collimation alone, the seeing won't allow you to see a sharper image anyway.

 

If a friendly member of your astronomy club knows how to collimate an SCT, he or she can teach you in five or ten minutes.  That's how I learned.

 

Good luck.  The C11 is a really good scope.


  • bluenote, wrvond and Tangent like this

#5 bluenote

bluenote

    Explorer 1

  • *****
  • topic starter
  • Posts: 75
  • Joined: 25 Nov 2012
  • Loc: San Francisco Bay Area

Posted 06 August 2021 - 09:35 AM

Many thanks Macdonjh.....I had a feeling that a laser collimator might not do it.  Will give the daytime method a shot!  



#6 macdonjh

macdonjh

    Fly Me to the Moon

  • *****
  • Posts: 6,763
  • Joined: 06 Mar 2006

Posted 06 August 2021 - 01:13 PM

Yeah, the problem using lasers with Cassegrains is the curved secondary mirror surface.  In the case of SCTs/ classical/ Dall-Kirkhams/ Ritchey-Cretiens, the convex mirror causes the laser's beam to diverge so the return beam is really a return blob.  Hard to center that on your laser collimator.



#7 luxo II

luxo II

    Skylab

  • ****-
  • Posts: 4,328
  • Joined: 13 Jan 2017
  • Loc: Sydney, Australia

Posted 06 August 2021 - 05:02 PM

OP You don’t need one. The only user - adjustment is the alignment of the secondary mirror, and for that a star test is simple, and effective.


Edited by luxo II, 06 August 2021 - 05:03 PM.


#8 mac57

mac57

    Viking 1

  • *****
  • Posts: 654
  • Joined: 19 Feb 2013
  • Loc: DeLand of Oz, Florida

Posted 06 August 2021 - 05:22 PM

The classic star test is the answer.


  • clusterbuster likes this

#9 MarMax

MarMax

    Surveyor 1

  • *****
  • Posts: 1,516
  • Joined: 27 May 2020
  • Loc: Los Angeles

Posted 07 August 2021 - 11:44 AM

I would recommend either a Duncan or Tri-Bahtinov mask to assist with collimation. I find them very helpful but you need better than average seeing. I'd pick a star that is brighter than Polaris and use 300x magnification.

 

For my location in SoCal I'd say it's about a 1/5 or 20% chance that seeing is good enough to collimate. You can still attempt the initial collimation when seeing is below average, but doing the final adjustment will require better seeing.



#10 rmollise

rmollise

    ISS

  • *****
  • Posts: 23,512
  • Joined: 06 Jul 2007
  • Loc: US

Posted 07 August 2021 - 02:33 PM

Just about to get my first SCT, a Celestron C11 HD.  Never collimated an SCT before...So, can I use my Howie Glatter Collimator with Tu Blug to collimate it?

 

No. Using a standard laser collimator on an SCT is a recipe for miscollimation. The good news? The best tool is free:  a second magnitude star. :)


  • ShaulaB and clusterbuster like this

#11 ShaulaB

ShaulaB

    Gemini

  • *****
  • Posts: 3,280
  • Joined: 11 Oct 2012
  • Loc: Missouri

Posted 07 August 2021 - 04:24 PM

Just my opinion,but collimating an SCT is easier then collimating a Newtonian. If you have done EAA, an eyepiece camera hooked up to a laptop can make this a breeze.

#12 bluenote

bluenote

    Explorer 1

  • *****
  • topic starter
  • Posts: 75
  • Joined: 25 Nov 2012
  • Loc: San Francisco Bay Area

Posted 10 August 2021 - 07:22 PM

All answers appreciated ....Looks like the single star test is the way to go for me.  Thanks everyone .




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