tegwilym

I'm getting basically nowhere with collimating our club's big 16 inch Ritchey Chretien. I've been reading a lot and asking questions on a FB page and other places. Has anyone here collimated with the following: Takahashi Collimation scope Autocollimating eyepiece What are the pros/cons of using these? The Takahashi is a lot more $$ and reading about the Autocollimator that seems to be a good alternative to get things lined up perfectly. I've spent probably over 20 hours on this over the last months. We bought the scope over a year ago, and still haven't had any good images on it due to the challenges. Either option will work, I can get funding from the club no problem - they know I've spent a lot of time on this already! I'm very interested in getting this working, we plan on doing a lot of "virtual" outreach during this virus pandemic, but nobody wants to see and hear me cussing online as I mess with the thing. If I can get something that I can get this working in a few hours - priceless! Chasing the collimation endlessly is just getting very old. Thanks in advance for any tips! Tom

Update: I did some more work on it yesterday using the sky through the open dome as an even background. Using the cheshire eyepiece I got everything as perfectly lined up as I could. I adjusted the focuser to point the laser at the center of the secondary, the reflected eyepiece hole appears in the middle of the secondary center circle after I adjusted the secondary mirror. Then I made everything centered again by moving the primary mirror. No matter what I do, I still see an uneven spacing around the primary and the baffle tube edge. I tried viewing Sirius but it clouded over before I could get spacing correct for focus. My latest question: Is it possible that the baffle tube could be slightly off center from the factory? I don't see that being a huge problem as long as mirrors are lined up. Then again, I see diagrams showing the same thing and it says the secondary needs to be adjusted. Gaaahh!!!! I'll need a clear night to see how my latest adjustments work to test out my baffle theory.

Thanks for the tips! Removing the secondary seems a little scary, but i did come across that .pdf file out there that someone showed that with a smaller 8 inch or similar. The other day I was out again messing with it. I think I made some progress since the stars were more round than before. I think part of the problem was that I was messing with the secondary incorrectly trying to even out the dark boundary around the view through a cheshire. I realized my mistake and now worked on centering the center dot of the secondary in the view of the cheshire - then carefully worked the primary a bit. I think with all this fiddling with this thing, if nothing else, I'm learning with way to twist things to move the mirrors where I want them. It was getting too dark (I used a sky background) when I was working on it, and will have to check again during the day and see how close I got it. Wow....these things are a pain, but I'll eventually get round stars! See our club page here: https://www.doorastronomy.org/ Tom

Good to know! I did buy the grid pattern for the Glatter but seem that the round one would be easier. Then again...t.his seems to be a beast to tweak no matter what!

I'm following this thread too. I just posted my own frustrations with my club's 16 inch RC that I've spent hours on. I wish I could get a round star like your example showed. If the star was round and focused I'd be tempted to leave it alone. I've got the focuser, primary and secondary all fiddled with now and just not getting anywhere.

I know this topic has been beaten to death already and I'm studying the posts of ideas. Just a little venting - I have access to our club's new RC 16 inch GSO Truss scope that I've been working on collimating. I've tried the Howie Glatter Grid pattern laser (seems the round pattern has been discontinued), a single spot laser to center the focuser, cheshire eyepiece, an Orion laser mirror collimator (the one with the 45 degree target - not sure the proper name at the moment), and a lot of visual attempts. I've spent HOURS working on this thing and have yet to get a decent round star. I have a good idea what I'm looking for and just have this question to toss out. When I get everything centered nicely yesterday, but the outer "daylight" ring of the primary wasn't even. I know that I need to adjust the primary, but then the secondary is messed up again. I know the order to collimate these is: 1) Focuser line up laser with center of secondary. 2) Adjust secondary 3) Finish up with Primary.....but then secondary is messed up again. *ugh!* Do I roughly center the primary with an even "ring" around it then go back to the secondary even if this isn't the correct order? But then I'm seeing the reflection of the primary in the mis-aligned secondary. Do I go back and forth between the primary and secondary, then do the proper order if the primary is somewhat lined up? Any good tips on this? I've been reading a lot about how to do this, tried many things, but just not getting it working right. I'm understanding the RC Collimation "nightmare" that I keep reading about is true! Thanks, Tom Door Peninsula Astronomical Society This is what mine looked like after lining things up symmetrically - but then the primary looked like this: (View through cheshire eyepiece to keep my eye in the middle) This is the scope that I'm working on...and it keeps beating me up!