RE: Stacking

["Michael Gutzwiller" <deepsky@fuse.net>]

Just for the record, Image Scientist does do sub-pixel stacking but it does
not do rotational adjustments, just linear.  Tom, do the stars at the edge
show rotational trailing after you stacked the images?

Mike G.

-----Original Message-----
From: owner-tass@listserv.wwa.com [mailto:owner-tass@listserv.wwa.com]On
Behalf Of Tom Droege
Sent: Monday, December 17, 2001 12:43 AM
To: tass@listserv.wwa.com
Subject: Stacking


Just for fun I used Image Scientist to stack 8 images from Data Set
20.  The result was as expected.  A reduction of signal to noise of the
square root of 8.  It seems to me that this is worth doing.  This gives the
equivalent of an eight hundred second exposure.  There are more stars to be
found at any one S/N setting.  It did not seem to take all that long.

This would give 7 data points over the 2 hour, 19 minutes that the sky is
tracked for these runs.  This would seem to be enough to show any trend.

Taking longer real exposures really reduces the dynamic range since the sky
brightness is so large.

I suppose that one could get the same accuracy result averaging the stars
after detection, but then this results in fewer detections.  Any comments?

With the stack, the bright pixels sure show up.  Since there was about a 10
pixel drift over the 1200 seconds of time covered by the eight 100 second
exposures, the bright pixels show up as little single pixel streaks where
the bright pixel is more or less constant.

Tom Droege