Ngc 2736

[JohnA]

Was testing out the c925 last night. I need to adjust the prism on the celestron OAG as i didnt get a full frame from my guide camera, almost like a half moon only. In saying that, it still managed to find guide stars easily enough and track well.

120sec x 83 frames
Celestron C925 NON edge
Celestron .63 reducer
Celestron OAG
ZWO 174 guide camers
ZWO 533MC pro
SVBONY SV240 filter
ASIAIR Plus

[muletopia]

A good one John, the stars are focused and the tracking looks good. But the stars, say upper right in your image, show tailing on their right. An optics problem? The flattener not working to the corners of the image?


I do like your picture.
Chris

[JohnA]

Thanks for the feedback Chris

I've never used the c9 for anything but planets so this is a first for me. Could be the reducer as I know the 533 on the svnony555 is spot on

Maybe the scope needs to be collimated?
I've yet to do it since I got it as when tje stars are out of focus the donut looked good and centred

[JohnA]

Chris, so i did some experimenting, and it would seem the issue is back focus.
That photo was taken at the 105mm backfocus.
I reduced the backfocus to 85 by removing the filter drawer and inserting the filter to the camera and the issue was much better, but still slightly there, easy to crop out though if i wanted to.
With the celestron OAG i cant get any closer backfocus without finding an appropriate SCT to M48 adaptor that will screw onto the reducer, the thread on all the ones i have seen are not long enough.
The only other option is to go the ZWO OAG-L but then i cant use my filter draw and have to get a filter wheel

[Leo.G]

Contact Jushua Bunn on here John, I'm sure he'd make you precisely what you need and I've heard nothing but good things about his machining.
I have a lathe, can't remember how to thread on the things, 25 odd years without one......I'll refresh my brain one day (or loose what little I have left) but I'll keep my rough, shoddy machining for my own projects where any loss is on me. I still have the big text book on machining, it has everything. I just have to remember where I put it or where my son put it, I bought the lathe and milling machine for him.


https://www.iceinspace.com.au/forum/showthread.php?t=167564&highlight=joshua+bunn

[JohnA]

Thanks for the Contact Leo. I'll reach out to him. In the mean time, i may design one on the 3d printer and been, only 11mm im thinking it should be more than strong enough, but would be a temporary fix only

[Leo.G]

3D printed stuff I see all of the time, personally I DO NOT like plastic printed stuff and won't have a printer here because my only use would be to make a sample of what I either want an engineer friend to make or what I want to make.
A temporary adapter though does get your camera right and could very well be worth doing.

In saying that I see many 3D printed projects here and one member offering the services for exactly that, also a lot of people using 3D printed equipment so I'm sure it is strong enough, I just prefer alloy.
Now a 3D sintered laser printer, that's on the cards when/if those lotto gods ever come through, I won't hold my breath!