Quote:
Originally Posted by Jason D
The autocollimator is a wonderful tool with the proper knowledge; however, it has to be of top quality. Not all autocollimators on the market (and there are only few choices) are equal.
Unfortunately, the autocollimator instructions provided in astrosystems documentation is incorrect. Even the theory behind the autocollimator described in the same documentation is incorrect.
The autocollimator is used for both secondary and primary axial alignment. You can refer to Vic Menard's CDP procedure for the proper method to use an autocollimator with a single central pupil
http://www.catseyecollimation.com/vicsCDP.html
I have written extensively about the autocollimator theory. Here is a link. Most of the info inside the link is academic and is not a required knowledge to use the autocollimator.
http://www.cloudynights.com/ubbthrea.../o/all/fpart/1
Jason |
Thanks very much Jason,
Very interesting. I'd been thinking of ordering one till I read what you just wrote.
Here is my question for you. I have a truss dobsonian which I have to assemble every time I use it. And every time, I have to use a Cheshire to make adjustments to get the little dark spot dead centre into the middle of the annulus in the middle of my primary. The more concentric the spot is in the annulus, the better the image.
Is it worth getting an autocollimator - other than for checking that something isn't slightly out with the secondary mirror (I was never that confident using the cross-haired sighting tube that I initially used)? Is it something I could get collimation right with in a minute or two after assembling and using the Cheshire? Or is it going to take another half hour of fiddling around?
Thanks for any assistance you can give me on this intriguing issue.
Regards,
Renato