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Collimation with a webcam??

Started by Astrovale, 12/15/2003 08:16AM
Posted 12/15/2003 08:16AM Opening Post
Hello guys,

I remember I read once on this forum that somebody used a webcam image on the pc screen to collimate his scope. It sounded very easy since you don't have to go back and forth from the screws in front to the eyepiece in the back and can check the effects of your adjustments "live" on your pc screen. However, it sounds too easy: can anyone tell me if this is a sound procedure or not? And, if not, why it won't work.

It would be indeed a great step towards facilitating a procedure that, on some scopes, proves to be very hard to perform. If you have a scope like the Nexstar 11 GPS, the whole system is too long for anybody that doesn't have the arm reach of a large primate, to be able to carry out the operations necessary to understand which screw to turn in order to adjust collimation. I wonder how people shorter than me (I'm approximately 5'11") can collimate a large SCT without a collimator!

Thanks for any help you can provide.

Gianluca

www.amun-ra.org
Solar Imaging Website
Posted 12/15/2003 08:33AM #1
Hi Gianluca,

Collimating with a webcam is an excellent method. Prior to getting my ToUcam, I always collimated my C-11 with a video camera. Now that I have a webcam it is easier because the laptop is always present for imaging and I don’t have to set up the TV monitor.

I use a 2X Barlow when the seeing permits (not very often) to get a larger presentation, but it is not necessary.

I have never seen an Airy disc with either my LX-90 or my C-11, so I cannot speak to the efficacy of the webcam collimation for the final, final stages of collimation – my SCT's optics and seeing don’t allow me to get that far.

Clear skies and easy collimating,

Dennis Persyk
Igloo Observatory Home Page http://dpersyk.home.att.net
Hampshire, IL

T7 comet image and movie http://home.att.net/~dpersyk/new.htm
Posted 12/25/2003 08:31AM #2
Hi,

Sorry to respond to this thread so late but I use a ToUcam to collimate my 12" LX200GPS frequently. I stand on a ladder with the LX200 hand controller in one hand and the other hand on the collimation knobs. On the recomendation of a friend, I make small collimation adjustments that do not drive the out of focus star image off of the display. I then use the hand control to recenter the star image. I also have never seen a airy disk. I collimate until I have centered the bright dot at the center of the out of focus star image. I have a difficult time determining when that has occurred, but I take my best guess. I am tempted to develop a tool that provides an overlay of a circle with a centered dot to help in this process. I move my scope in and out of the garage on wheeley-bars. I find that I must collimate each time that I roll the scope out because the driveway seems to be sufficiently rough to disrupt the collimation. I believe that the process that I am following is adequate because I have been successful at imaging the Encke Gap on several occasions following this process. Excellent seeing is also required. Here is a link to one of these images.
http://homepage.mac.com/joanlvh/Astronomy/SaturnHR.html

Merry Christmas
George