Quote:
Originally Posted by rmcpb
Some steps for you: - Loosen the three secondary screws enough to allow the secondary to pivot on the central bolt.
Turn it till the image of the secondary seen through the focuser is circular.
This circular image should be centred in the focuser by adjusting the central bolt up or down till it has an even margin all the way around the secondary. It may help to put some paper in the tube between the secondary and primary to stop the image of the primary confusing you at this step.
Adjust the three secondary screws till you can see the primary centred, if you use your laser it should hit the primary right in the middle.
Check the shape of the secondary image again and adjust if necessary. This will mean adjusting the secondary tilt.
Repeat this till the image of the secondary is centred in the focuser (this is where a Cheshire eyepiece is really handy), the image is round and the beam of your laser hits the primary in the centre.
Adjust the primary to get the return beam from the laser to retrace itself back to the laser hole.
It takes practice and time. This is not the "best" way to collimate but it is a definite step up from the hole in the film canister trick.
Cheers |
Hi leinad - as rmcpb says in the above.
Your:
"The central bolt will only loosen/tighten the mirror in order to either move it towards or away from the pri.mirror." is correct but as I pedantically keep saying' you should substitute "loosen/tighten" in your statement with "shift." Because this central bolt is a spring-loaded job, if you keep "tightening it" as in screwing it clockwise its spring will eventually become squished up on itself and no more turning will be possible - conversely, if you keep on "loosening it" as in turning it anti-clockwise the sec mirror and holder will fall off the spider with (possibly) disastrous consequences.
As rmcpb says, turning the central bolt/screw is for getting the mirror "centred" under the focusser tube: this means that when you look at it down the focusser tube the oval sec mirror will "appear" as if it is circular (round) and there will be a uniform gap all around it relative to the focusser tube's bottom end (ie appearing like a circle within the focusser tube's circle)
As rmcpb also says, neither a pinhole in the cap of a film canister nor a laser collimator are the proper tools for this procedure, and I suggest he is endorsing the "sight-tube/chesire" as a fitting device for this procedure just as I do.
Regards, Darryl.