#1  
Old 10-07-2009, 01:02 PM
pmrid's Avatar
pmrid (Peter)
Ageing badly.

pmrid is offline
 
Join Date: May 2008
Location: Bribie Is.
Posts: 3,124
Ritchey Chretien's and image curvature.

I be grateful to hear of other people's experiences with the GSO RCs - particularly the 8". It's amazing how little information there seems to be on the architecture and optical design of the GSO scopes. There is a bit, but not a lot on RCs generally, and the RCOS site is certainly interesting but if you are looking (as I am) for specific info on how the GSO versions perform with a DSLR (as opposed to a large format CCD camera), then you'll be disappointed (or have to lean new skills in Googling the right keywords).
I'm reading that the GSOs have no coma but significant image curvature. I'm afraid I don't know what that means. It's part of what I'm trying to find out - I think.

Peter
Reply With Quote
  #2  
Old 10-07-2009, 01:55 PM
jase (Jason)
Registered User

jase is offline
 
Join Date: Sep 2006
Location: Melbourne, Victoria
Posts: 3,916
Hi Peter,
I have no experiences to share with regards to the GSO RC's. Everyone is quick to give an opinion, I'll refrain from doing so as it provides little value.

Now to coma and field curvature confusion. I would recommend some research courtesy of telescopes-optics.net;
COMA
FIELD CURVATURE

You can obtain more information on optics from their site;
http://www.telescope-optics.net/

Cheers
Reply With Quote
  #3  
Old 10-07-2009, 02:20 PM
gregbradley's Avatar
gregbradley
Registered User

gregbradley is offline
 
Join Date: Feb 2006
Location: Sydney
Posts: 15,409
Hi Peter,

I wouldn't worry about the curavture in the GSO RC. Judging by Paul's images it simply is not an issue. Any RC has curvature. I had a 12.5 inch RCOS and it had curvature and you can buy a special field flattener for it for US$1500. Is it worth it? No. But there is some minor improvement mainly to the star sizes off axis.

Greg.
Reply With Quote
  #4  
Old 11-07-2009, 12:32 PM
Satchmo's Avatar
Satchmo (Mark)
Registered User

Satchmo is offline
 
Join Date: Dec 2005
Location: Sydney
Posts: 1,858
If someone can give me an approx. figure for backfocus ( primary to focal plane) and the seperation from primary to secondary, I can reverse engioneer the design and post some raytrace spot diagrams without a field flattener.
Reply With Quote
  #5  
Old 11-07-2009, 02:39 PM
pmrid's Avatar
pmrid (Peter)
Ageing badly.

pmrid is offline
 
Join Date: May 2008
Location: Bribie Is.
Posts: 3,124
Hi Mark. I just took delivery of a GSO RC 8" today. If you can sketch out a rough graphic of the measurements you need, I'll certainly send them down.
Jase and Greg: Thanks for your input.

Peter
Reply With Quote
  #6  
Old 11-07-2009, 05:19 PM
Tandum's Avatar
Tandum (Robin)
Registered User

Tandum is offline
 
Join Date: Apr 2008
Location: Carindale, Brisbane.
Posts: 4,112
Pete,
I found a page on Proper Positioning of a Focal Reducer
on a Ritchey-Chrétien Cassegrain Telescope
which may come in handy.
Get the calculator out
Reply With Quote
  #7  
Old 21-07-2009, 01:01 PM
Geoff45's Avatar
Geoff45 (Geoff)
PI rules

Geoff45 is offline
 
Join Date: Jul 2006
Location: Sydney
Posts: 2,407
Quote:
Originally Posted by jase View Post
Hi Peter,
I have no experiences to share with regards to the GSO RC's. Everyone is quick to give an opinion, I'll refrain from doing so as it provides little value.

Now to coma and field curvature confusion. I would recommend some research courtesy of telescopes-optics.net;
COMA
FIELD CURVATURE

You can obtain more information on optics from their site;
http://www.telescope-optics.net/

Cheers
Nice site!
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 08:45 PM.

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