Duncan mask

[dbowie]

Hi anyone here used or using the Duncan mask method for SCT collimation, any hints, advice on design etc, seems to be pretty open ended, chrz

[billdan]

Hi Brenton,

I have done collimation with a Hartmann mask for my Newt, but found a barlow laser method easier and more accurate.

I do have this pdf on the Duncan mask though.

[Troy]

The Duncan mask is a good starting point for defocused collimation especially if you don't know how far to defocus the telescope before starting the collimation process.
For best results always collimate with a focused star ;)

[dbowie]

Ok thnx for replies Ive collimated my C8 and 9.25 just using out of focus star with no probs but I spotted the Duncan mask on several other forums and thought an IIS member perspective would be good and perhaps a few people here might have been interested in the concept. Just found this, (http://www.iceinspace.com.au/index.php?id=63,187,0,0,1,0)
I see the Hartman is along the same lines. Im gonna make one anyway and try it, thnx..