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Old 05-11-2011, 11:35 PM
Carl
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RC8 collimation

Just had a go in my Observatory at collimating my new RC8 using a real star. Pain the but actually. Viewing was poor, star kept moving out of frame when i made slight adjustments and i needed to be contortunist to bend around the scope to hold the hex keys and view the monitor. There's got to be a simple way, surely?

I've seen plenty of ads for artifical star collimators. Sounds a lot more convenient and apparantly you dont need to wait for a clear night for steady viewing.

Any suggestions?

Cheers
Carl
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Old 06-11-2011, 12:34 AM
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ReaPerMan (Paul)
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Quote:
Originally Posted by Carl View Post
Just had a go in my Observatory at collimating my new RC8 using a real star. Pain the but actually. Viewing was poor, star kept moving out of frame when i made slight adjustments and i needed to be contortunist to bend around the scope to hold the hex keys and view the monitor. There's got to be a simple way, surely?

I've seen plenty of ads for artifical star collimators. Sounds a lot more convenient and apparantly you dont need to wait for a clear night for steady viewing.

Any suggestions?

Cheers
Carl
Hi Carl
I was put on to the Cats eye by Brendan and Grahame and I used a combination of the Cats eye Auto collimator and a Hotec Laser Collimator to get things close. The real improvement is then in the star testing as this is were all the effort pays off.

I have the artificial star but you need to set it up at about 30 -40 meters to get the best result. Persevere with the star testing but from my experience get a friend around to give you a hand as it's definately easier with 2 people.. unless you have arms like an indian death goddess

An alternative is the Tak collimation scope (very expensive) this is 2.7" and needs several adaptors to fit it to the RC (but worth every penny i'm told ) in the end.

hope this helps.

All the best

Paul
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Old 06-11-2011, 10:45 AM
Carl
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Collimation tools

Hi Paul
Thanks for the reply.
I live on 5 acres so there is no problem about distance for setting up an artificial star test. I suppose the question is: is an artificail star test more accurate and easy to do than pointing the scpe at a star at night and doing it that way?

Interesting add on to the above. Yesterday i used my Cheshire collimation tool to get the secondary perfectly centred only to discover at night thru the scope that when out of focus my mirror was way out. Viewing was very bad last night. Checked my scope this morning and it is way out of whack when viewed with the cheshire collimator.

Does the artifical star give a more accurate collimation guide?

Any suggestions from the community welcome
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Old 06-11-2011, 11:06 AM
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ReaPerMan (Paul)
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The artificial star is a great help and the ease is a stable light source with no atmospherics to worry about but the true test comes when pointing at the sky. Picking a star near the zenith and seeing the performace with full weight on the mirror shows up any problem. Also I won't tell you how to suck eggs but the sequence of adjust secondary, adjust primary then adjust secondary again is vital. Once you have finished this process you must take a picture with your defocused star in the middle and each of the four corners of your field this will reveal any distortions that remain. If you find (as I did ) that you have one corner that is 'out'. you then adjust the primary into the direction of the error. This rapidly overcomes most of the collimation error but be careful it gets down to a ridiculously fine amount of adjustment. mine is now close but I probably have about a 1/16 of a turn left to get it right!!

good luck

Paul
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Old 06-11-2011, 11:19 AM
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Marke (Mark)
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I use a Tak coll scope for my 10" and it is a quick easy process and you dont need lots adapters . I just happen to have one handy off my oag but its just a 2.7 - 2" nose piece , screw it onto the front and pop it
in the focuser. Its not cheap but no worse than fancy laser collimators and a lot simpler.
Mark
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Old 06-11-2011, 11:48 AM
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RickS (Rick)
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The thread on the Tak Collimating scope is M36.4P1 male. Vixen used to have some adapters to fit but they don't make them any more. The best option I found is the Borg #7423 adapter (http://www.sciencecenter.net/hutech/.../html/7423.htm) which will let you attach the collimating scope to a male T-Thread. Alternatively, if you happen to have a Tak refractor lying around then you probably have a suitable adapter already (one of the widgets used for 1.25" eyepieces has a M36.4P1 female thread).

Cheers,
Rick.
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