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grignr
newbie


Reged: 02/06/12

Help! Out of colimation new
      #5723042 - 03/09/13 09:46 PM

I have a Nexstar 6SE. I am horribly out of colimation. Any ideas will help. I do have a laser colimator. I tried to colimate it, but with no success.
Thank you ahead of time.


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sanlopez
sage


Reged: 12/03/07

Loc: 35.9606° N, 83.9208° W
Re: Help! Out of colimation new [Re: grignr]
      #5723106 - 03/09/13 10:39 PM

A laser colimator does not work on your telescope. For rough collimation set your telescope perpendicular to a white wall and then take out the eyepiece and look down the barrel of the diagonal. What you want to see is a perfectly round donut, with the secondary mirror centered in the "white" primary mirror, and your eye's reflection centered on the barrel. If it is not, then try adjusting the 3 anchors of the secondary (screws of allen bolts) until all circles sit perfectly in one another. Then you can do a proper collimation on a star

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Tel
Postmaster
*****

Reged: 03/31/06

Loc: Wallingford England
Re: Help! Out of colimation [Re: sanlopez]
      #5723452 - 03/10/13 07:11 AM

Hi grignr,

Welcome to CN and to this forum !

Assuming you are familiar with the collimation procedure as a whole, (and please let us know if you are not), you may find the following links of use to you when you come to carry out the operation.

http://www.starrynights.us/Articles/Collimation.htm

and

http://www.cloudynights.com/ubbthreads/showthreaded.php/Cat/0/Number/4387535/...

As Santos has advised, your laser collimator will not help with the collimation of your 6SE or any other Schmidt-Cassegrain 'scope.

Given then, that following his instructions your 'scope proves to be not too far out of collimation and that the "doughnut" shape he invites you to view, appears to have a dark centre, (cast by the secondary mirror), concentric with the white surround of the primary mirror, then to proceed in gaining greater accuracy of alignment, a star test, or artificial star test is the only real means of aligning the secondary mirror with the primary.

Note though and of great importance, that when making any adjustments, each adjustment screw should only be moved a fraction at a time.

Hoping this helps,

Best regards,
Tel


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Bob Griffiths
Getting Grouchy
*****

Reged: 10/10/05

Loc: Frederick Maryland
Re: Help! Out of colimation new [Re: Tel]
      #5723839 - 03/10/13 12:40 PM

If you are not familiar with the procedure to collimate a Sct and or feel uncomfortable with it you may want to contact a local astro club and ask for help... I know both of my astro clubs gets these kinds of requests from time to time and we always find a club member more then willing to help out

Its really quite simple and as noted you do not need any tools other then an allen wrench or screw driver and a clear view of any star of medium magnitude Polaris does not move so it is the star of choice

As noted do not even think about using a laser to collimate your scope...

Bob G.

Bob G.


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grignr
newbie


Reged: 02/06/12

Re: Help! Out of colimation new [Re: Bob Griffiths]
      #5724704 - 03/10/13 08:28 PM

Thank you for your help. This will definitely help me.

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Geo.
Carpal Tunnel
*****

Reged: 10/01/08

Loc: Upstate NY
Re: Help! Out of colimation new [Re: grignr]
      #5730082 - 03/13/13 11:03 AM

Look, I do this all the time and I really can't work out all those mirroring and flip-flops in my head. While looking through the eyepiece, I place a finger at the corrector pointing at the point where the shadow of the secondary (donut hole) is closest to the outer donut ring. I've figured out that where the the hole is pinching the ring is where it has to be pulled away from the primary and adjust the screws accordingly. Once you make and adjustment You must remember you have to RECENTER the donut in the field of view and check your adjustments. For large long scopes you can make a pointer with a clip and tougue depressor. Hope this helps.

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FlyBD5
sage
*****

Reged: 02/12/13

Loc: Boston MA
Re: Help! Out of colimation new [Re: grignr]
      #5748934 - 03/22/13 01:22 AM

Quote:

I have a Nexstar 6SE. I am horribly out of colimation. Any ideas will help. I do have a laser colimator. I tried to colimate it, but with no success.
Thank you ahead of time.




Get a set of Bob's Knobs for your 6SE and use the collimation instructions that come with it. It is very easy to do and a very good $20.95 investment for your OTA.


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Arthur Dent
Galactic Hitch-Hiker
*****

Reged: 10/23/08

Loc: South Yorkshire, UK
Re: Help! Out of colimation new [Re: FlyBD5]
      #5749756 - 03/22/13 01:43 PM

Just install one of Bob's Knobs at a time.

If you loosen all three, the secondary will fall off and, like as not, hit the primary mirror!

Art


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Arctic_Eddie
Post Laureate
*****

Reged: 12/30/07

Loc: St. Petersburg, FL
Re: Help! Out of colimation new [Re: Arthur Dent]
      #5749934 - 03/22/13 03:16 PM

It's also a good idea to collimate after replacing each screw. You can do it in the daytime using a small shiny object a few blocks away. Sunlight reflecting from a small curved object makes a useful artificial star. Light bulbs, Christmas tree ornaments, marbles, or anything glassy and reflective are fine.

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hopskipson
Pooh-Bah


Reged: 06/24/10

Loc: Queens, New Yawk, Light pollut...
Re: Help! Out of colimation new [Re: Arctic_Eddie]
      #5750385 - 03/22/13 06:54 PM

Hotech makes a laser collimator for SCT's. It will set you back $455

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Jammer53
super member


Reged: 12/18/12

Loc: Central NY
Re: Help! Out of colimation new [Re: hopskipson]
      #5765447 - 03/29/13 06:07 PM

Quote:

Hotech makes a laser collimator for SCT's. It will set you back $455






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Peter9
Post Laureate
*****

Reged: 10/30/08

Loc: Yorkshire - Born & Bred
Re: Help! Out of colimation new [Re: Jammer53]
      #5766159 - 03/30/13 04:49 AM

From what i've come to understand from the guys on this forum, there's is no need for a laser collimater when collimating a SCT scope.

Regards. Peter.


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Arctic_Eddie
Post Laureate
*****

Reged: 12/30/07

Loc: St. Petersburg, FL
Re: Help! Out of colimation new [Re: Peter9]
      #5766211 - 03/30/13 06:48 AM

The collimation of an SCT is the act of tilting the secondary mirror so that it's longitudinal axis is parallel to that of the primary, but not necessarily coaxial. There is no reasonable way of doing this from the rear with a lasing device. The only practical way is to view a slightly defocused point of light and adjust for concentricity in the observed light rings.

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