#1  
Old 22-03-2009, 08:25 AM
Tilt's Avatar
Tilt (Michael)
Registered User

Tilt is offline
 
Join Date: Jan 2008
Location: Brisbane
Posts: 556
WO 0.8x focal reducer/flattener - thoughts?

Hi guys,

Sorry, this is not a thread about IF I should buy one ect

Just asking if anyone else uses a WO 0.8x FR/FF to correct curvature, I've been using one lately with an ED80 however some nights it seems to work better than others. Last night I imaged a chunk of the LMC (including NGC 2070), and the edges of the image look a little suss (stretched, elongated stars). Where as other times I have used the WO flattener, I've had a nice flat field in the images. Any one else recieving random results like I am

Michael
Reply With Quote
  #2  
Old 22-03-2009, 08:36 AM
Octane's Avatar
Octane (Humayun)
IIS Member #671

Octane is offline
 
Join Date: Dec 2005
Location: Canberra
Posts: 11,159
Michael,

http://www.iceinspace.com.au/93-458-0-0-1-0.html

Regards,
Humayun
Reply With Quote
  #3  
Old 22-03-2009, 09:09 AM
darrellx's Avatar
darrellx (Darrell)
Registered User

darrellx is offline
 
Join Date: Dec 2007
Location: Kulgun, Queensland
Posts: 278
Michael

Yes I do. I was just considering a similar post when I read yours. I have a Megrez90 and use the WO 0.8x and generally I am happy with the results I get. But sometimes, like you, the objects around the edges of the shots are stretched and look like there has been some rotation.

I don't know what causes it,or whether I am doing something to make it happen. All I do at the moment is crop the image to remove the offending objects.

You are not alone.

Darrell
Reply With Quote
  #4  
Old 23-03-2009, 09:12 AM
Geoff45's Avatar
Geoff45 (Geoff)
PI rules

Geoff45 is offline
 
Join Date: Jul 2006
Location: Sydney
Posts: 2,631
Just guessing here, but maybe the field is still a little curved. If you get good focus in the centre, the edge will be out, but if you focus somewhere between the centre and edge or if your centre focus is not spot on, you may get a reasonable average focus over the whole field.
Geoff
Reply With Quote
  #5  
Old 23-03-2009, 04:08 PM
[1ponders]'s Avatar
[1ponders] (Paul)
Retired, damn no pension

[1ponders] is offline
 
Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
Another thing to consider is if there is sag in your camera to scope connections. I have to take care at times to make sure the camera is held squarely in the focuser draw tube, otherwise I do get problems with stars in parts of images.
Reply With Quote
  #6  
Old 23-03-2009, 08:20 PM
Tilt's Avatar
Tilt (Michael)
Registered User

Tilt is offline
 
Join Date: Jan 2008
Location: Brisbane
Posts: 556
These are all very good thoughts.

Yes I suppose I shouldn't be looking for perfection with a $400 ED80 + flattener, I guess its not possible. Interestingly the results I get are varied, so sometimes the edges are fairly ordinary, and sometimes its very good. So the camera being square on the draw tube might certainly be an issue (I know the flattener moves around a bit as I'm locking it into place). I appreciate the comments.

Michael
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 10:30 AM.

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