Re: [APML]: New Image

[Chuck Vaughn <aa6g@aa6g.org>]

The Astro-Photography Mailing List
------------------------------------

Ian,
>
>U really need to qualify this statment a bit for 35mm this is a true
>statment. However as the film  gets larger either 6 * 7 or 4 * 5. 
>
>A longer time Star drift is required due to the greater FOV on the larger
>negative.

Maybe Dave would be so kind as to rework his formulas for medium format
and a 1 meter focal length. I'm not aware of anyone on APML doing full
frame 4X5 work.

The AP 7"-f/7 gives a 4" circle which is means the edge is 2" off axis
and Dave calculated for 1" off axis.

I still think that my criteria of no drift in 5 minutes (or at least 
less than I can see) will work for the larger formats. It should cover 
the vast majority of cases for us amateurs.

There are limits to drift alignment and it's impossible to get perfect
alignment anyway. I wouldn't want to try a four exposure at +80 with
a large format.<g>

Chuck  <aa6g@aa6g.org>