Click here if you are having trouble logging into the forums
Privacy Policy |
Please read our Terms
of Service | Signup and
Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User
Levine
super member
Reged: 03/24/06
Posts: 128
Loc: Indiana, Wabash County
|
|
Ok, here's the scoop:
Picked up a nice C11 Carbon fibre fastar tube, and decided to - you guessed it - replace those pesky screws with focus knobs.
In the process, the tube fell about 18" off its perch to the carpeted floor. No tinkling sounds or cracked mirror (thank God), and the focus mechanism remained smooth.
I then (with not a little concern) proceede to start recollimating, with an artificial star.
My first view was the scene smeared off to the right.
No amount of fiddling with the knobs would fix it.
I then removed the secondary assembly and confirmed that the secondary was tipped about thirty degrees off level.
I carefully levelled the mirror by direct sight, and tightened down the knobs. The secondary was then replaced.
The view was improved somewhat, but not as much as I would have hoped.
I had to stop there, as the CFO had other tasks for me that could not wait.
What should my next steps be? Is there a way for me to check the integrity of the primary and its tracking, without resorting to a disassembly?
...I PROMISE not to drop the OTA again...! 
  
--------------------
JMI NGT-18 Reflector, "Magellan"
C11 CFT XLT Fastar, "Dave"
CotoSKY 8.25" f/6 Achromat, "Blackjack"
Meade AR6 Achro, "Kalliopi"
WO FLT 110 Apo, "Apollo"
Coronado PST "Icarus"
Canon IS 15 X 50 Binoculars
Losmandy G11/Gemini4
Discmounts DM-6, Sky Commander, StarBeam
Denk II Universal Power X Switch Binoviewer
Collins I3/Astronomik H-a/Starsweeper
...and some nice glass.
|
SanDiegoPaul
professor emeritus
Reged: 07/22/05
Posts: 596
Loc: San Diego
|
|
This may just be a case for a laser collimator. While their use in an SCT is very marginal, it will tell you in which direction it's (a mile) off so that you can center the secondary on the primary.
At RTMC this year I got one from Howie Glatter with the SCT adapter which lifts the laser unit out of the eyepiece holder and the side is cut open. You look into the side, and you can see where the laser beam is being directed/reflected to.
In my case I used it just once - It showed the laser beam as being directed directly into the center of the bullseye so to speak. So I used it once and haven't touched it since. I figure that it will come in handy with some other scope down the line though so I'm keeping it.
My point is though, that if I had seen the laser beam directed to the outer edge of the field, this would have been a terrific way to center it. Then under the stars, the collimation could be fine tuned.
--------------------
Meade 10" Lx200-R with Moonlight SCT Focuser
Mitty Evolution Wedge
AT-80 Guide Scope
SBIG ST402ME CCD Imager
Canon Digital Rebel DSLR
Meade DSI-c CCD for Guiding
Please visit my gallery!
http://www.pbase.com/sandiegopaul/
|
rmollise
Carpal Tunnel
Reged: 07/06/07
Posts: 1534
|
|
Quote:
Ok, here's the scoop:
Picked up a nice C11 Carbon fibre fastar tube, and decided to - you guessed it - replace those pesky screws with focus knobs.
In the process, the tube fell about 18" off its perch to the carpeted floor. No tinkling sounds or cracked mirror (thank God), and the focus mechanism remained smooth.
I then (with not a little concern) proceede to start recollimating, with an artificial star.
My first view was the scene smeared off to the right.
No amount of fiddling with the knobs would fix it.
I then removed the secondary assembly and confirmed that the secondary was tipped about thirty degrees off level.
I carefully levelled the mirror by direct sight, and tightened down the knobs. The secondary was then replaced.
The view was improved somewhat, but not as much as I would have hoped.
I had to stop there, as the CFO had other tasks for me that could not wait.
What should my next steps be? Is there a way for me to check the integrity of the primary and its tracking, without resorting to a disassembly?
...I PROMISE not to drop the OTA again...!
Getting a scope back in the "ballpark" is easy. Stand about 6 feet from it looking dead on at the corrector. Observe the reflections in the primary. Are they concentric? Adjust collimation until they are. That will put you back to the point where you can do a "normal" collimation.
And, no, don't drop that kitty no more. 
--------------------
Uncle Rod
Watch for Rod's New Book:
Choosing and Using the New CATs--coming soon!
|
|
5 registered and 5 anonymous users are browsing this forum.
Moderator: Jason B
Print Thread
|
Forum Permissions
You cannot start new topics
You cannot reply to topics
HTML is disabled
UBBCode is enabled
|
Thread views: 278
|
|
|
|
|
|
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
[Re: 