#1  
Old 11-02-2016, 11:25 AM
pjphilli (Peter)
Registered User

pjphilli is offline
 
Join Date: Jan 2008
Location: Thornleigh Sydney
Posts: 638
RC Artefact

Hi

I have a GSO RC 8in f8 scope. The attached image shows a reflection artefact (from the secondary baffle?) when stretching a composite of a wider image of the Flame nebula with the nearby bright Alnitak star.
Any suggestions for a fix of the cause of this artefact?

Cheers peter
Attached Thumbnails
Click for full-size image (RC Artefact.JPG)
3.4 KB56 views
Reply With Quote
  #2  
Old 11-02-2016, 12:44 PM
billdan's Avatar
billdan (Bill)
Registered User

billdan is offline
 
Join Date: Mar 2012
Location: Narangba, SE QLD
Posts: 1,551
Gooday Peter,

I think you will find that a bright star reflection is bouncing off the CCD chip and then reflected back off the CCD glass window and bouncing back onto the chip.

I get this with Alnitak and M45 bright stars as the attached crop shows.

Very annoying and not much that can be done about it. People say that by removing the glass window and re-installing it slighty tilted will fix the problem.

Regards

Bill
Attached Thumbnails
Click for full-size image (m45 11x300 dark bias DSS-crop.jpg)
142.9 KB51 views
Reply With Quote
  #3  
Old 11-02-2016, 02:03 PM
glend (Glen)
Registered User

glend is offline
 
Join Date: Jun 2013
Location: Lake Macquarie
Posts: 7,033
A low reflectivity sensor coverglass like the Astronomik MC Clear will prevent that. I have one in my modded DSLR and get no reflection problems with my RC08.
Reply With Quote
  #4  
Old 12-02-2016, 02:31 PM
pjphilli (Peter)
Registered User

pjphilli is offline
 
Join Date: Jan 2008
Location: Thornleigh Sydney
Posts: 638
Thanks Bill and Glen for this advice. I have only had this trouble with
imaging the Flame with Alnitak close by. Alnitak can be nudged off the
direct view but I rather like the dramatic effect of the Flame next to Alnitak.
I guess that the problem could be reduced by taking a lot more shorter
images for stacking and thus reducing the need for heavy stretching of the composite.
The very heavy dew laden skies over Sydney lately are not helping matters either.
Cheers Peter
Reply With Quote
  #5  
Old 13-02-2016, 04:38 PM
Paul Haese's Avatar
Paul Haese
Registered User

Paul Haese is offline
 
Join Date: Jan 2009
Location: Adelaide
Posts: 9,937
This is a common reflection from an RC with bright stars. Generally I try to avoid very bright stars.
Reply With Quote
  #6  
Old 14-02-2016, 03:16 PM
pjphilli (Peter)
Registered User

pjphilli is offline
 
Join Date: Jan 2008
Location: Thornleigh Sydney
Posts: 638
Thanks Paul
I know that the closeness of the very bright star to the Flame is a big
ask to obtain a good stretched image of the nebula. This is a pretty exceptional case to be avoided where possible. Normally, I have no problems with such bright star artefacts. Pleased to know that it is not
an uncommon experience and not just due to my ineptitude!
Cheers Peter
Reply With Quote
Reply

Bookmarks

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 07:28 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement