From: Milton Aupperle <milton@outcastsoft.com>
Date: May 19, 2010 2:40:40 PM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: [Astro_IIDC] Tarantula nebula..NGC 6744.. Jupiter
Mark;
On 19-May-10, at 2:03 PM, Mark Gaffney wrote:
Hi Milton,
I may be a bit stupid but I can`t get my head around how exactly to do this measurement?
Why don't READ that "Using the CROAG" document I sent you several months which has pictures in it that shows how to do this on the first page?
All I can think is to measure how far apart the two cameras are on my shipping container.
You don't do that.
You measure the distance from the telescope end of the OAG (that's the part attaches to the back of the Telescope / or Focal reducer) to the front of the CCD in each camera.
If the CCD's in both cameras are exactly the same distance to the front of the OAG, they are parfocal, which means both will be in focus at the same time. That's unlikely and you may need to add or remove extenders and then slide the Guide camera in or out of the holder to get them both in focus.
Once you have the distances so they are close, you'll need to fine tune it a little bit to get sharp focus with both cameras and that's where your 80 meter sign comes in.
Milton Aupperle