Re: [ATM] Collimating from the eyepiece.

[Mike Lockwood <melockwo@uiuc.edu>]

Clive,

Clive Rogers wrote:
> Some years ago I remember reading in I believe it was Sky and Telescope and 
> article of someone who attached knobs and rods along with all the necessary 
> equipment to his telescope to collimate his primary without leaving the 
> eyepiece area.  Does any one if this is about on the internet.  

Quite a few have done this.

I do this on my 16" F/4 (with rods).  (Of couse I can also do it on my 
Cassegrain.)

My 16" page is: 
http://bi-staff.beckman.uiuc.edu/~melockwo/telescopes/16in_F4/16in_F4.html

The back of the mirror cell is shown in the second to last photo, and 
at the bottom of the "triangle" that holds the mirror, you can see the 
ends of two bolts that tilt the mirror assembly (triangular part). 
The heads of these bolts point up, towards the top of the scope, and I 
slide rods down through pipes that are attached to the inside of the 
mirror box.

The rods have sockets attached to the end of them, and they fit the 
bolt heads.  The pipes prevent the metal sockets from ever touching 
the primary.  The tops of the rods are visible in the first three 
photos.  The rods are wood, and they are easy to see among the 
aluminum truss poles.  The tops of the PVC pipe "guides" are visible 
in the third to last photo, to the upper left and right of the opening 
in the mirror box (my accessory box is sitting in the mirror box in 
this photo).

I use a "moving frame" type mirror cell - it has several advantages. 
First, the mirror retaining clips can be set very close to the mirror, 
which keeps it from rattling around much.  Second, the mirror edge 
supports move with the mirror.  Third, any part of the frame that 
extends outside of the shadow of the primary is a possible connection 
point for remote collimation rods.

To collimate, I stand at the eyepiece and move the star towards the 
"tail" of any coma that I see.  Recenter the star, and repeat.

No gearing, motors, wiring, etc. required, it's a direct connection 
once the rods are inserted.  The rods fit inside two of the truss 
poles for storage.

	Mike Lockwood

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