From: "jimchung2338" <jim_chung@sunshine.net>

Date: April 9, 2008 2:17:43 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Mathematics of Stacking

Hi all,

I'm giving a talk on planetary imaging for members of the Toronto RASC

group and have always wondered about the math of stacking.  This is

what I feel and welcome comments:

1.   Stack the sharpest number of frames at a high cutoff like 90%

even if its only a hundred frames since the firewire cameras we use

here are much less noisy than webcams we don't need to reduce noise by

stacking several hundred frames and have sharp details diluted by

poorer frames.

2.  If I'm doing a LRGB image I would do #1 for L channel and then

stack several hundred frames at a lower cutoff to reduce the noise

that usually accompanies turning up the gain to image through RGB filters.

3.  Is there a mathematically determined number of frames were

additional stacking produces diminishing returns in quality.

Thanks!

Jim