SV: ATM A few questions before I screw my Dob together for the first time..

["Nils Olof Carlin" <nilsolof.carlin@telia.com>]

Peder,

>I have used a black marker to darken the edge of the diagonal mirror, should
>I do the same for the primary?  

I'm not sure if the "edge" you refer to is the outermost part of the mirror face, or the 
cylindrical cut around it. If the latter, I think it is important to blacken the 
secondary over the part visible from the focuser, but I can't see any point in doing the 
same for the primary.

>Also, should I put a mark or a sticker in
>the center of the primary to aid in collimation?  

It certainly makes the collimation easier, using a Cheshire-like collimator. Even if you 
plan to star tweak the last bit, it will get you a lot closer before this.

>Lastly, I remember reading
>about making a collimation tool from a 35mm film container, but I can't seem
>to find the reference now that I need it.  Any replies appreciated.  Thanks
>for reading.

You may find some ideas on
http://zebu.uoregon.edu/~mbartels/kolli/kolli.html
about how to make collimation tools - and what they are supposed to do, and what to 
accomplish with them.


Kurt Maurer suggested:

>For the film can collimating tool, get an ordinary plastic 35mm film 
>can and cut the bottom off. Then drill a 1/16" diameter hole in the center of 
>the film can's cap, using the molding dimple to find the center. Put the cap 
>back on the can, and voila! you have a collimating tool. It will fit into a 1 
>1/4" focuser perfectly.
>To gussy it up and make it more "professional", cut 1/16" to 1/8" 
>strips of aluminum foil and glue 'em to the inside of the film can's cap, 
>centered on the hole, to make "crosshairs". Then you'll have an official Al 
>Kelly Collimating Tool!!

I may misunderstand you here Kurt, but you really make me curious - do you mean you glue 
the foil strips on the inside of the cap over the drilled hole in it? How do you use them 
for collimating?

Regards,
Nils Olof