Old 10-10-2012, 04:55 AM
TanjaC (Tanja)
Registered User

TanjaC is offline
Join Date: May 2012
Location: Johannesburg, South Africa
Posts: 30
Is there a problem with my optics?

Hi Guys - I've re-collimated my C11 since removing the secondary mirror for my Hyperstar. I don't know if it was like this prior to using the Hyperstar, as I used it 'new out the box' - but spotted this collimating.

Although there might be a few dust donuts etc this looks different to me, and subsequently I always feel like I'm not collimated perfectly. In some images I feel the stars are still flared or "pac-man" like - but that might be me being over critical now, as I'm not using a field flattener on the C11 SCT.

A very out of focus star seems okay, but as it approaches focus there seems to be something bottom left.

Is it normal - should I be worried? I can't spot any obstruction in my OTA.

Attached Thumbnails
Click for full-size image (collimation.jpg)
103.4 KB65 views
Reply With Quote
Old 10-10-2012, 07:23 AM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 19,126
If the scope wasn't cool it could be a tube current. Otherwise did you shim the secondary cell in the corrector in anyway? Sometime using shims other than cork or paper or too tight can slightly stress the glass when it gets cold and the central hole contracts around the secondary. Nothing major to worry about though. Finally make sure the three collimation screws at the back of the secondary are not too tight.
Reply With Quote
Old 10-10-2012, 07:24 PM
Paul Haese's Avatar
Paul Haese
Registered User

Paul Haese is offline
Join Date: Jan 2009
Location: Adelaide
Posts: 9,575
That is 100% tube currents. Cool the scope for 4 hours outside and then test the scope. You will find it to have a different result.

Feel free to look at my site on cooling an SCT in the how to section.
Reply With Quote
Old 10-10-2012, 07:38 PM
asimov's Avatar
asimov (John)
Planet photographer

asimov is offline
Join Date: May 2005
Location: Bundaberg
Posts: 8,819
Tube currents
Reply With Quote
Old 11-10-2012, 04:41 AM
TanjaC (Tanja)
Registered User

TanjaC is offline
Join Date: May 2012
Location: Johannesburg, South Africa
Posts: 30
Originally Posted by Paul Haese View Post
That is 100% tube currents.
Great - I'll try again. I cooled it in a separate room as it was actually too hot outside during that day and temp drops at night.

Yip - made sure the screws are not too tight, Thanks Marc. They were very tight when I first did collimation.

Awesome - great to know it's not something wrong with it - thanks guys.
Reply With Quote


Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT +10. The time is now 06:41 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Lunatico Astronomical
Astronomy and Electronics Centre