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C 9.25 WAY out of collimation! HELP!

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#1 LateViewer

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Posted 26 August 2014 - 06:53 AM

I have a C9.25 that I have moved many times in the last 3 years and have used little.  Recently I took it out to use and found it WAY out of collimation.  Could someone point me in the direction of recovering gross alignment?

 

I know how to collimate when it needs "adjusting" but this is way beyond that.

 

Thanks

 

Al S



#2 rmollise

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Posted 26 August 2014 - 07:58 AM

I have a C9.25 that I have moved many times in the last 3 years and have used little.  Recently I took it out to use and found it WAY out of collimation.  Could someone point me in the direction of recovering gross alignment?

 

I know how to collimate when it needs "adjusting" but this is way beyond that.

 

Thanks

 

Al S

 

My major concern is "What got it so far out?" If it were correctly collimated in the first place and didn't have something wrong with it, it SHOULD NOT lose collimation, not to this extent, no matter how many moves you've made.

 

Anyhow, to get it back in the ballpark, stand two meters in front of the corrector and look straight down the tube. Adjust the collimation (by tightening screws) till all reflections are concentric. You can then proceed to collimation using a star. ;)


Edited by rmollise, 26 August 2014 - 07:59 AM.


#3 LateViewer

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Posted 26 August 2014 - 10:26 AM

Good question as to what happened.  I wonder if a screw backed out? 

 

Thanks for the answer Rod

 

Al



#4 Ed Holland

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Posted 26 August 2014 - 11:44 AM

One method that I have used to restore rough alignment is described in this link http://www.robincasa...ro/collimation/

 

It has the advantage that one can get most of the way there - often close to something resembling a lop sided diffraction pattern with subsequent star testing -  in a lighted room without fiddling in the dark.

 

After that the usual process of testing under the stars, and fine adjusting whilst approaching closer and closer to actual focus takes over - but you know that part already ;)

 

Best of luck.

Ed



#5 tonyt

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Posted 26 August 2014 - 07:20 PM

If you have a 50 foot clear run indoors you can use a hubble artificial star to collimate in the daytime at high power since the scope will be thermally stable (leave the heater off). I find this much more relaxing and effective than trying to collimate in my usual falling night time temperatures.

While looking through the eyepiece if your hand is obstructing the skinny part of the rings you need to tighten the screw nearest the hand, or if it's between two screws tighten both of those, or loosen screw/s on the opposite side of the secondary.

If you're a really long way out of collimation the central spot will move outside of the rings - if you can figure out which side it has moved out of treat that side as the skinny side of the ring pattern.

I remember how to adjust the screws in relation to the defocused rings by thinking if I'm fat I need to loosen my belt, so a screw needs to be loosened at the fat part of the rings or tightened at the skinny part of the rings.

#6 David Pavlich

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Posted 26 August 2014 - 09:18 PM

What I did in your case was to put in a low power eyepiece like a 27 Panoptic.  Find a bright star like Vega and center it.  Now take it way out of focus until you have a fairly large donut.  If your collimation is as bad as you say, even with the big donut, it'll appear off center.  Get the big donut centered remembering to recenter the donut after every correction.  Once done, you'll at least have rough collimation.  From  there, you can use a high power eyepiece and do a proper collimation using the normal collimation routine of just a slightly out of focus star.

 

David



#7 LateViewer

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Posted 29 August 2014 - 07:18 AM

 

I have a C9.25 that I have moved many times in the last 3 years and have used little.  Recently I took it out to use and found it WAY out of collimation.  Could someone point me in the direction of recovering gross alignment?

 

I know how to collimate when it needs "adjusting" but this is way beyond that.

 

Thanks

 

Al S

 

My major concern is "What got it so far out?" If it were correctly collimated in the first place and didn't have something wrong with it, it SHOULD NOT lose collimation, not to this extent, no matter how many moves you've made.

 

Anyhow, to get it back in the ballpark, stand two meters in front of the corrector and look straight down the tube. Adjust the collimation (by tightening screws) till all reflections are concentric. You can then proceed to collimation using a star. ;)

 

 

Hey Rod,

 

As to what got it so far out of collimation; I think it probably happened when I was attempting to install a set of Bob's knobs. 



#8 rmollise

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Posted 29 August 2014 - 12:19 PM

Ah-ha! Installing Bob's Knobs is rougher on Mr. Scope than just them country roads. :lol:


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