ATM Collimating Dots should be small

[David Sleeter <sleete19@idt.net>]

Tom Glinos, x4302 wrote:
> 
> >The dot on the diagonal will do no harm. The center of the diagonal
> >has a shadow of its self just like the primary. The very center
> >of the diagonal is not used.
> 
> How big of a dot can be used?
> 

Hi Tom. It's Dave Sleeter. A smaller dot is best because it makes a more 
precise target to look at. When I bought and sold telescopes as a second 
business, I collimated DOZENS of Newtonians, and I used a "Sharpie" 
black indelible marking pen. A Sharpie makes a highly visible, very 
black, nice and small dot that is an ideal target for collimating. I put 
a similar dot in the exact center of the primary mirror as well. I left 
these dots on the mirrors permanently, and when I sold each telescope, I 
would explain to each new owner how to use them, and that they did NOT 
show up in or affect the field of view.

To find the center of the secondary, draw its exact likeness with a CAD 
program (if you don't have a CAD program, find a neighbor or someone at 
work who does), put a dot in the geometric center of the drawing (the CAD 
program will locate it for you) and print it out actual size on a laser 
printer. Carefully and ACCURATELY cut out the paper secondary with a pair 
of scissors, cut or punch a tiny hole right through the paper where the 
dot is, lay the paper secondary gently over the real secondary, position 
it carefully, put the point of the "Sharpie" through the hole in the 
paper, and make the mark.

Dave Sleeter  
-- 
Life is short and the path is often unclear.
It is a great sin to knowingly contribute to someone's confusion.