Re: [ATM] Odd collimation problem

["James Lerch" <jlerch1@tampabay.rr.com>]

----- Original Message ----- 
From: "Chris Dalla Piazza" <dalchri@hotmail.com>


> With my CCD rig, I collimate my f/4.5 Newtonian scope by defocusing and
> using the donut pattern created by the shadow of the secondary mirror.  I
> usually try to pick a region of the Milky Way so I'll have lots of stars.
> Then I look for the part of the picture where the secondary mirror shadows
> all seem to point.  I take this point to be the optical axis. Then I use the
> collimation bolts to center this point on the CCD chip.

Your secondary, focuser, or both, are out of collimation.  By collimating using 
only the primary, you are able to get the optical axis of the primary to hit the 
center of the ccd, it just isn't hitting the center of the ccd square (i.e. the 
optical axis isn't perpendicular to the surface of the CCD).

If you use a simple site tube, you'll probably see most of the error right away.

Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)
http://lerch.no-ip.com/ChangFa_Gen (My 15KW generator project)

"Anything that can happen, will happen" -Stephen Pollock from:
"Particle Physics for Non-Physicists: A Tour of the Microcosmos"

" Press on: nothing in the world can take the place of perseverance.
Talent will not; nothing is more common than unsuccessful men with talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent. "
                                                           Calvin Coolidge 

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