Can a Celestron C102-HD Refractor be collimated?
Posted 11 May 2013 - 03:45 AM
I'll try and pull it apart today if I have time. I'm working nights on the weekends so I won't be able to check out the view until Monday.
Posted 11 May 2013 - 09:12 PM
Posted 12 May 2013 - 01:04 PM
Posted 12 May 2013 - 05:32 PM
This is also the grease you can replace the Synta glue in the mount gears....
Posted 14 May 2013 - 02:21 AM
Took out the lenses from the lens cell. They didn't appear to have been taken apart. They had 3 metallic looking spacers that had some double stick tape adhesive on both sides. I gently pried them apart, which I think was a mistake, but I had to see if a backwards element was the issue. I'd marked the edges so they could be realigned again. I cleaned them and put them back into the plastic lens cell.
There's some serious miscollimation in the whole scope. My collimation tool shows very bad issues with the draw tube focuser and diagonal.
I took the diagonal out and just used the focuser and the EPs to look at Saturn and Spica again. The view still sucks with bad distortion as I've previously described.
I'll try and tighten up the slop in the focuser and the collimation angles at it's attachment point on the tube with the 3 screws.
I'm not giving up yet, but I sure wish I had a nicer scope that just worked without all the drama.
GoTo with tracking sounds wonderful too. The CG-4 GEM has more slop than a hog trough.
To be continued...
Posted 14 May 2013 - 07:38 AM
The OTA's not warped or anything is it??? Probably is the focuser. S&S Optika in Denver has a used focuser from an Celestron 102XLT (pretty much same scope as the C-102HD) for like $30 (somebody swapped it out) that should fit. Maybe give them a call (websearch "S&S Optika", they'll pop up in your browser. This is a small scope shop in Denver, they don't do internet sales, but will deal over the phone...) Good Luck!
Posted 14 May 2013 - 09:46 AM
Posted 14 May 2013 - 01:35 PM
Posted 15 May 2013 - 02:31 AM
It's looking like the lens cell itself is badly out of alignment relative to the OTA body. It mounts with 3 countersunk screws so the dew shield can slide over and onto the cell against a stop flange. There isn't any easy way to fix this as it's not adjustable. I tried rotating the cell one hole at a time and none of those positions fixed the miscollimation issues. One of the screw holes in the steel OTA tube is somewhat stripped and another is not perpendicular to the body surface. Looks like either the previous owner screwed it all up putting it back together or it was one of the lemons produced by sloppy worksmanship at the Synta telescope factory back in 1999.
I'm not sure how to fix this so it's robust enough to stay collimated even when the dew shield gets taken on and off and gets the occasional bump going through doorways etc.
Posted 15 May 2013 - 09:21 AM
Posted 15 May 2013 - 10:13 AM
I can't in good conscious re-Craig's list this thing unless I can get it fixed. So it's a good thing I'm only into it for the $150 I originally paid. The subsequent eye pieces I've invested in were needed in any event for any and all other scopes I'll get in the future.
Note to self:
If you can't star test a used scope before you buy it, you have to roll the dice.
Posted 15 May 2013 - 10:26 AM
Posted 15 May 2013 - 10:38 AM
Posted 17 May 2013 - 06:13 AM
Looks to be a good replacement OTA. I don't know if the mounting rings I have will fit.
Posted 17 May 2013 - 08:02 AM
Posted 17 May 2013 - 10:05 AM
I just don't have the bux for the good scopes right now.
Later this summer maybe I can get a good setup, but for now I'm scopeless save for this low cost OTA.
Craig's list hasn't had anything decent for months now. Mostly kids junk toys or over priced antiques.
Posted 17 May 2013 - 11:43 AM
Posted 17 May 2013 - 11:55 AM
Not sure if this was already brought up or not. Can't you just elongate the existing holes in the tube or in the cell with a dremel tool or something and then get the cell to align better with the tube, you will have more adjustment room then.
Posted 17 May 2013 - 03:26 PM
Looks like my mounting rings will be too large for a simple plug and play approach.
The tube is no longer 114 mm in diameter, it's now 102 mm, which means the OTA isn't baffled as well as before (there are 3 on mine.)
Mine definitely has some good baffles.
Posted 17 May 2013 - 05:20 PM
Posted 17 May 2013 - 06:57 PM
Posted 21 May 2013 - 01:53 PM
I'm not going to toss the broken OTA, but it's a lot easier to work on if it's not your only scope. No pressure to get it working asap.
If I still get stumped, I will have a shipping box to send it out for a second opinion from a more experienced astro guy.
Posted 24 May 2013 - 07:41 PM
I'll keep peeking outside tonight for any cloud breaks long enough to do some star tests and look at a planet or two.
Most of next week will be cloudy too