#1  
Old 02-08-2014, 10:44 AM
trent_julie's Avatar
trent_julie
Registered User

trent_julie is offline
 
Join Date: Nov 2008
Location: Canberra
Posts: 572
Rc8 odd rings

Hi Everyone,
I have caused an image defect on my RC8. Pictured are the rings that appear in each of my images no matter the direction I am facing. I am happy that I know the cause of the elongated stars, but the rings confuse me.

My imaging system has undergone several changes simultaneously so it is difficult to isolate a potential candidate. But here is the list of changes so far;

New Orion off-axis guider
New Moonlite 2 inch to t-thread adapter
New Bob's Knobs for secondary

I am using an Orion parsec 8300 Monochrome, with 2 inch filters. This is the same configuration as 2 years ago when I last imaged without the aforementioned defects.

I know that a flat will illuminate the issue but I would rather deal with the cause.

I believe that the secondary might be too far from the primary as a result of installing the Bobs Knobs, but I am unsure on how to prove this either way. Any help would be greatly appreciated.

Cheers,

Trent
Attached Thumbnails
Click for full-size image (CCD-Image-93.jpg)
76.8 KB41 views
Click for full-size image (CCD-Image-101.jpg)
110.5 KB42 views
Reply With Quote
  #2  
Old 02-08-2014, 11:08 AM
alocky's Avatar
alocky (Andrew lockwood)
PI popular people's front

alocky is offline
 
Join Date: Aug 2010
Location: perth australia
Posts: 1,287
Hi Trent, the worst you could do with the secondary being in the wrong position is cause vignetting or slightly hurt your contrast, since the scope has still come to focus - same with the new T-adapter. If your secondary is not well positioned your collimation will also be problematic, but won't cause the effect you're showing. Is there anything reflective in the OAG? This really looks like a stray light issue to me, so some shiny metal exposed in the imaging train - and - a new source of light off axis.
cheers,
Andrew.
Reply With Quote
  #3  
Old 02-08-2014, 08:06 PM
Paul Haese's Avatar
Paul Haese
Registered User

Paul Haese is offline
 
Join Date: Jan 2009
Location: Adelaide
Posts: 9,392
I would put out an ask for someone to measure their secondary to primary baffle. That will give you the correct distance. Take a mean measurement from several scopes.
Reply With Quote
  #4  
Old 03-08-2014, 06:48 AM
DJT (David)
Registered User

DJT is offline
 
Join Date: Nov 2011
Location: Sydney
Posts: 1,352
Hi Trent
I also put an oag on my Rc8 last week and now have a fine set of rings very similar to yours.

Am assuming flats will sort it out
Reply With Quote
  #5  
Old 03-08-2014, 10:36 AM
trent_julie's Avatar
trent_julie
Registered User

trent_julie is offline
 
Join Date: Nov 2008
Location: Canberra
Posts: 572
Thanks everyone.
As it turns out it was because of reflections. During the day I used matt paint on my 2inch - t adapter. Additionally I used a "Sharpie" on some areas of the OAG this resolved the issue.

Paul,
Thanks for your advice. My focal length measurements for the rc8 as seen on a solved pinpoint image is 1608mm. I hope this might help someone else.

Trent
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 09:20 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Celestron Australia
Advertisement
SkyWatcher Australia
Advertisement
OzScopes Authorised Dealer
Advertisement
Bintel
Advertisement
Lunatico Astronomical
Advertisement
NexDome Observatories
Advertisement
Meade Australia
Advertisement
Astronomy and Electronics Centre
Advertisement