ICEINSPACE
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Moon Phase
CURRENT MOON
Full Moon 99.6%
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28-04-2006, 11:48 AM
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Looking Down From Above
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Join Date: Dec 2005
Location: Cootamundra, NSW
Posts: 1,711
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A couple of little tip's that you might want to consider. Every three or four months, run the focuser fully out and in a couple of times to keep the baffle grease distributed evenly and if you are removing the OTA from the mount regularly, check the machine screws that hold the front corrector ring in place, they can loosen over time and give the indication that the scope is going out of collimation, things I have learnt from experience.
JohnG
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28-04-2006, 12:58 PM
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Planet photographer
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Join Date: May 2005
Location: Bundaberg
Posts: 8,819
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When I received my C9.25 I checked all screws on the OTA for firmness. Some were only just finger tight. Pays to check 'em over periodically.
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28-04-2006, 02:05 PM
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6000 post club member
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Join Date: Oct 2005
Location: Launceston, Australia
Posts: 6,570
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Well.. what do ya know!!!
I just checked the screws on the front corrector ring and yes, they were not done up particularly tight.
I've given them a moderate-firm tightening. I wasn't sure whether tightening too hard could potentially cause distortion of the corrector?
I was also worried it might crack if it's screwed down too tight when it expands/ contracts in changing temp conditions? Is that possible if you've got the corrector rings screwed too tight?
Also, does tightening the screws cause a little shift in collimation because you're moving the corrector ever so slightly?
But those screws were not particularly tight!!! 
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28-04-2006, 02:11 PM
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Whats visual Astronomy
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Join Date: Dec 2004
Location: Brisbane
Posts: 5,062
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More then likely...its a very sensative area.....just check collimation tonight Matt...hope this fixes your problem.
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28-04-2006, 02:19 PM
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Looking Down From Above
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Join Date: Dec 2005
Location: Cootamundra, NSW
Posts: 1,711
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Just tighten them up firm, you should have no problem with stressing the corrector, it is held in place by 4 small shims to allow for expansion, just keep the screwdriver away from the corrector face.
You will have to re-collimate but it should hold now.
JohnG 
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28-04-2006, 05:33 PM
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Planet photographer
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Join Date: May 2005
Location: Bundaberg
Posts: 8,819
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If you wanted to get technical, you could find out the recommended torque values for these screws so you can use a torque wrench on them...that way their all the same. Although you can probably guage yourself how tight they all are by feel.
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28-04-2006, 06:26 PM
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6000 post club member
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Join Date: Oct 2005
Location: Launceston, Australia
Posts: 6,570
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 How would you find the torque values for those?!?!
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28-04-2006, 07:12 PM
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Planet photographer
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Join Date: May 2005
Location: Bundaberg
Posts: 8,819
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From Celestron....they made the darn thing....or designed it or whatever!?
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28-04-2006, 07:38 PM
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Planet photographer
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Join Date: May 2005
Location: Bundaberg
Posts: 8,819
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But why bother. I'm sure it would be too hard to get that kind of info out of anyone...Celestron included
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28-04-2006, 07:54 PM
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6000 post club member
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Join Date: Oct 2005
Location: Launceston, Australia
Posts: 6,570
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Precisely. Hence my prior question 
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28-04-2006, 08:57 PM
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Looking Down From Above
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Join Date: Dec 2005
Location: Cootamundra, NSW
Posts: 1,711
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Must be cloudy up there tonight 
JohnG
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28-04-2006, 08:59 PM
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6000 post club member
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Join Date: Oct 2005
Location: Launceston, Australia
Posts: 6,570
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Up where, John???
Looks like it's cloudy right across the east of oz
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28-04-2006, 09:10 PM
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Looking Down From Above
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Join Date: Dec 2005
Location: Cootamundra, NSW
Posts: 1,711
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Was trying to be funny re the previous couple of posts, meant Canberra, socked in down here.
JohnG
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28-04-2006, 09:30 PM
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6000 post club member
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Join Date: Oct 2005
Location: Launceston, Australia
Posts: 6,570
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Oh OK.
Yeah... Asi sounds a little "off" tonight?
He'll be Ok once the clouds clear and he gets a few more jupiter pics
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28-04-2006, 10:01 PM
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Planet photographer
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Join Date: May 2005
Location: Bundaberg
Posts: 8,819
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Well, I haven't got a problem with shutting the hell up & going away I guess..... 
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28-04-2006, 10:22 PM
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6000 post club member
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Join Date: Oct 2005
Location: Launceston, Australia
Posts: 6,570
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Asi...
Could you explain what you mean by that?
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28-04-2006, 11:50 PM
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Planet photographer
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Join Date: May 2005
Location: Bundaberg
Posts: 8,819
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Ah.....I possibly had one of those annoying 'internet misinterpretations'....U know, 'reading into' comments?
Forget my last comment.
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29-04-2006, 09:31 AM
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Dazzled by the Cosmos.
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Join Date: May 2005
Location: Brisbane
Posts: 11,826
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Just checked all my C9.25 screws/bolts and all were nice and tight. Must have had a good one - phew!
Do be careful though. Some are meant to be removed so you can add accessories, such as a finder scope bracket, mounting rails, etc. Some are meant NOT to be removed as they hold important elements in place, such as the corrector plate holder, etc.
Cheers
Dennis
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29-04-2006, 10:49 AM
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Registered User
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Join Date: Mar 2006
Location: Victoria
Posts: 864
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Its not a Celestron SCT thing - My C8 seems to hold collimation extremely well , and I havent noticed any shifts when in different parts of the sky. I am using bobs knobs, but dont think that would make any difference.
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29-04-2006, 12:13 PM
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Looking Down From Above
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Join Date: Dec 2005
Location: Cootamundra, NSW
Posts: 1,711
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Matt
If you are considering keeping your SCT, might I suggest a book, Choosing and Using a Schmidt Cassegrain Telescope, by Uncle Rod, probably the best book written on the subject, he has over 25 years experience with SCT's, similar to mine.
One of the best books written on the subject.
Cheers
JohnG
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