Come join the friendliest, most engaging and inclusive astronomy forum geared for beginners and advanced telescope users, astrophotography devotees, plus check out our "Astro" goods vendors.
Come join the friendliest, most engaging and inclusive astronomy forum geared for beginners and advanced telescope users, astrophotography devotees, plus check out our "Astro" goods vendors.
A few weeks ago a wind storm came through and blew over my entire imaging rig. The biggest issue that has arose are the optics in my 8rc. Collimation was atrocious when I checked it. I have been using a star test for collimation as well as a cheshire eyepiece. I know in the images below the donuts arent PERFECTLY centered but Im noticing an artifact in each unfocused star at about 5 o'clock... The focused stars look triangular in shape.. not like poor collimation but moreso pinched optics. This wasnt a problem before the fall.. How may I diagnose this issue or figure out which component of my scope is causing the issue? Im hoping the OTA is not bent. Its a carbon fibre OTA.. the fall resulted in a few scratches but thats the only physical damage that I could see.
If you have any more questions about my collimation procedure or the incident, let me know.
UlteriorModem wrote: ↑Sat May 25, 2019 1:44 pm
That would be one heluva thing if you 'bent' a carbon fiber tube. Even if it was bent I don't thing it would pinch the mirror.
Your collimation looks pretty good. The top image shows some signs of 'wobble' in the tracking. Check the drive train for backlash.
Also check your centering of the secondary. It is critical for RC scopes.
Yeah I don’t think it’s bent.. the top image is only a 5 second exposure so I don’t believe there’s any wobble.. that’s just the shape of my stars which leads me to believe there is stress on the mirror at the point where the mirror clips hold the mirror.
I havnt checked the position of the secondary yet.. Best way to do this is measure the spider canes I’m assuming?
Yea it is a pain on an RC. Personally I use a Howie Glatter laser. I suppose you could use the Cheshire if you have one. I guess you could measure the vanes. While your at it check them for any twist. Another way is to cut out a circle the same diameter as the OTA fold it a couple of times like a pie slice and nip the sharp point off leaving a small hole in the 'exact' center. Then place that over the OTA to check it out.
Only way to be sure about the mirror cell is to open it up!
BTW; Why was your scope out un tethered in a storm? I leave mine out covered 24/7 but drove stakes and tied down the mount with some rope.
These are the stakes I used.
Tom
Current Equipment:
Mount: Celestron CGX-L
Scope: 130mm f7 APO
Cam: ASI071mc-pro
[quote=UlteriorModem post_id=5763 time=1558803996 user_id=75]
Yea it is a pain on an RC. Personally I use a Howie Glatter laser. I suppose you could use the Cheshire if you have one. I guess you could measure the vanes. While your at it check them for any twist. Another way is to cut out a circle the same diameter as the OTA fold it a couple of times like a pie slice and nip the sharp point off leaving a small hole in the 'exact' center. Then place that over the OTA to check it out.
Only way to be sure about the mirror cell is to open it up!
BTW; Why was your scope out un tethered in a storm? I leave mine out covered 24/7 but drove stakes and tied down the mount with some rope.
These are the stakes I used.
[/q uote]
I actually had a Howie Glatter but found that because my focuser is stock, it has a bunch of slop and collimating the RC with the HG led to poor collimation and oblong stars so I stopped using it. It does seem that I may have to open it up. The spiders don’t look twisted or deformed in anyway but that’s just me using my eyes as judgement lol. I wouldn’t mind taking the OTA apart.. I usually end up taking all my equipment apart when an issues arises anyways! Haha.
