ATM (no subject)

[Gary Myers <gmyers@CetLink.Net>]

Richard Keppler wrote:
  Shim the focusser until you can see
> that the laser dot does not move when the focusser is racked to and
> from either extreme.

This is not, I am sorry to say, a good means of checking the focus axis.
It is however a good means of checking the "runout" (correct mechanical
term) in the focuser and another problem with truly obtaining
collimation with all eyepieces!.

I have posted a means to setup the focus axis. The other issue is the
runout of the focuser. Racking the focuser in and out - if the runout is
0, the desired amount, will show a centered non moving dot (independent
of the focus axis alignment. The laser shows this extremely well. The
only focusers that I have tried are JMI NGF3, and NGF2. The 3 has runout
- the dot moves around quite a bit. The 2 does not - the dot stays dead
nuts centered. JMI is fully aware of this - it has to do with the
ability to put more pressure on the better bearings used in the 2 and
not the 3.

G.