#1  
Old 16-12-2019, 10:14 PM
lazjen's Avatar
lazjen (Chris)
PI cult member

lazjen is offline
 
Join Date: Dec 2012
Location: Flaxton, Qld
Posts: 1,747
Camera and FF/FR for SV 70 ED?

I recently got a Stellarvue SV 70 ED with no flattener or reducer. I've done some googling and see a few options around the 0.8x reducer. Would a "Orion Focal Reducer 0.8x for Refractor" work? I couldn't find references that matched the 70 ED scope to that FR. Any other options, especially just a suitable 2" flattener (the "Orion Field Flattener"?).

Ideally, I'd like to use this as an option for a travel setup, so I'm considering getting a cooled OSC to go with it, although I'm a bit concerned since it's just an ED doublet. I'm thinking of doing some tests with my DSLR to see what the colour is like. Assuming it's ok, what would be a good cooled OSC to go with it?

If OSC doesn't work, I might just drop back to my ASI1600MM-C + Filters for now (it would mean camera swapping though).
Reply With Quote
  #2  
Old 20-12-2019, 09:21 PM
lazjen's Avatar
lazjen (Chris)
PI cult member

lazjen is offline
 
Join Date: Dec 2012
Location: Flaxton, Qld
Posts: 1,747
Ok, I can now answer one of my questions - not getting an OSC. Managed to do a test with the DSLR and the colour wasn't great.

Also, most definitely needs a FR or FF when used with a DSLR.
Reply With Quote
  #3  
Old 21-12-2019, 10:57 PM
Camelopardalis's Avatar
Camelopardalis (Dunk)
Drifting from the pole

Camelopardalis is offline
 
Join Date: Feb 2013
Location: Brisbane
Posts: 4,696
Chris, you'd almost certainly want (at least) a field flattener as the radius of curvature is quite tight on a small refractor, so you'll most likely see a fair bit of field curvature even with the 1600.

I've not used the Orion reducer myself, but the Televue TRF 0.8x is reportedly good on small, fast-ish refractors.
Reply With Quote
  #4  
Old 22-12-2019, 07:25 AM
lazjen's Avatar
lazjen (Chris)
PI cult member

lazjen is offline
 
Join Date: Dec 2012
Location: Flaxton, Qld
Posts: 1,747
You're 100% correct actually Dunk - it will still need something because that field curvature is quite apparent.

I got in contact with StellarVue and the 0.8x for the SV70T works for the ED as well. However, I'm taking a punt on the Orion 0.8x working as well (grabbing the one that was advertised here recently). If it doesn't, well I'll sell that off and get the more expensive version.
Reply With Quote
  #5  
Old 22-12-2019, 10:11 AM
Camelopardalis's Avatar
Camelopardalis (Dunk)
Drifting from the pole

Camelopardalis is offline
 
Join Date: Feb 2013
Location: Brisbane
Posts: 4,696
Cool! Don’t be surprised if you need to play the game of “find the spacing sweet spot”, with any flattener or reducer...it doesn’t always match the manufacturers claims
Reply With Quote
  #6  
Old 22-12-2019, 12:24 PM
The_bluester's Avatar
The_bluester (Paul)
Registered User

The_bluester is offline
 
Join Date: Feb 2011
Location: Kilmore, Australia
Posts: 2,231
The ED80 reducer/corrector that Skywatcher sell with the Evostar 72 needed closer to 60mm than the advertised 55 in my setup.
Reply With Quote
  #7  
Old 22-12-2019, 02:13 PM
Xeteth (David)
Registered User

Xeteth is offline
 
Join Date: Jul 2019
Location: Melbourne, Australia
Posts: 72
Quote:
Originally Posted by The_bluester View Post
The ED80 reducer/corrector that Skywatcher sell with the Evostar 72 needed closer to 60mm than the advertised 55 in my setup.
What's the best way to test this? I'm assuming taking pictures and checking them in CCDInspector?
Reply With Quote
  #8  
Old 22-12-2019, 03:26 PM
lazjen's Avatar
lazjen (Chris)
PI cult member

lazjen is offline
 
Join Date: Dec 2012
Location: Flaxton, Qld
Posts: 1,747
Ah, great to know. What a surprise that there's variance with these things.
Reply With Quote
  #9  
Old 22-12-2019, 03:44 PM
The_bluester's Avatar
The_bluester (Paul)
Registered User

The_bluester is offline
 
Join Date: Feb 2011
Location: Kilmore, Australia
Posts: 2,231
If you have CCD inspector that is a good option but you can get a pretty decent handle on it visually as well.

Seems that for most correctors (Sensor spacing on a RASA seems to be the opposite) if you have radial streaks (Warp speed0 in the corners the sensor is too close to the sensor, if you have arcs (Fishbowl) it is too far away.
Reply With Quote
  #10  
Old 22-12-2019, 03:50 PM
lazjen's Avatar
lazjen (Chris)
PI cult member

lazjen is offline
 
Join Date: Dec 2012
Location: Flaxton, Qld
Posts: 1,747
Click image for larger version

Name:	Reducer-CCD-distance.jpg
Views:	27
Size:	87.1 KB
ID:	253434

I grabbed this image off a post in IIS a few years ago I think. Very useful visualisation of the problem.
Reply With Quote
  #11  
Old 03-01-2020, 10:01 PM
lazjen's Avatar
lazjen (Chris)
PI cult member

lazjen is offline
 
Join Date: Dec 2012
Location: Flaxton, Qld
Posts: 1,747
I've got the Orion 0.8x reducer now, and there's a few holes in the clouds tonight. I haven't quite got the spacing correct, but I'm not too far off and I can see that most of the frame seems fine. I think with suitable experimentation on the exact back focus required, I can expect this reducer to work.
Reply With Quote
  #12  
Old 04-01-2020, 10:10 AM
Nikolas's Avatar
Nikolas (Nik)
Dazed and confused

Nikolas is offline
 
Join Date: May 2012
Location: Melbourne
Posts: 1,450
I know this isnt very helpful but I used the orion 0.8 field reducer on my ts 130 and it seemed to do the job, not 100% perfect but a fairly decent flat field
Reply With Quote
  #13  
Old 04-01-2020, 10:33 AM
lazjen's Avatar
lazjen (Chris)
PI cult member

lazjen is offline
 
Join Date: Dec 2012
Location: Flaxton, Qld
Posts: 1,747
That's what I'm expecting - not 100% perfect, but fairly decent flat field overall.

I've done some more swaps to the spacing to bring it closer to the alleged correct spacing, so tonight I hope to do some more tests.

On another note, I've added the ZWO EAF to it now. Biggest hassle was the mounting bracket for the focuser. The screws supplied didn't match the mount points on the scope, so I've improvised with some others.
Reply With Quote
  #14  
Old 04-01-2020, 10:00 PM
lazjen's Avatar
lazjen (Chris)
PI cult member

lazjen is offline
 
Join Date: Dec 2012
Location: Flaxton, Qld
Posts: 1,747
So damn typical - I just got everything setup tonight, configured various bits of software, etc, and the clouds rolled in.



*sigh*
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 10:00 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Advertisement
Lunatico Astronomical
Advertisement
Bintel
Advertisement
Celestron RASA
Advertisement
Testar
Advertisement
Star Adventurer
Advertisement
Astromechanics
Advertisement
EQ8-R
Advertisement
Astronomy and Electronics Centre
Advertisement