Re: ATM Laser Collimators and helical focussers.......

["clement.focuser" <clement.focuser@verizon.net>]

> Now back on topic, in our groups 10 inch f4.5 we have got a helical
> focusser. After centre dotting the primary/secondary I find that when I
use
> the laser collimator the beam makes a circle of approximately 1/2" to 3/4"
> as I turn the focusser. I can centre the beam fine but if I then turn the
> focusser 180deg the beam is displaced by that amount. Any suggestions?
> I have checked the collimator using vee blocks for alignment and there is
very
> little runout of the beam.

Did you check the laser collimator  for roundness?  An out of round
collimator tube that has lobes may check out OK in a  90* V block. But will
not be centered in another V block with a different angle or in the focuser.
I use a BB type V block with two contact angles for this reason. see
http://www.1gg.com/html/body_fixbblocks.html

Don Clement
Running Springs, California
Owner: Clement Focuser
My focuser is non rotating, has an ultra low profile of 1" with 3" of travel