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Old June 19th 07, 03:52 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Default ASTRO: Common object uncommonly processed

I'm sure the ADU counts I listed for the core are more reflective of the
efficiency of the AB gate on that pixel than of the actually photon
count. By 50k the count is completely unreliable. I try and limit the
brightest parts of the object I'm taking to less than 30k for this
reason. It is quite linear below 30k but above that the individual ab
gates seem to start adding noise. It's so small as to be meaningless to
the photo, not photometry however, until you hit about 45k. Above that
all bets are off. Most of the time only stars reach that level so its
not a problem but the core of the Cat's Eye is so bright it hits that
level in about 2 minutes at 2x2 binning even through a color filter (not
narrow band). At that time the outer shell would be barely out of the
noise. It could be done in one shot but I doubt it would look as good
as it would with separate short shots for the core. Your type of chip
would be far superior for this, even the ST-7's chip being non abg would
do better though it would barely fit the FOV. I'll go the two exposure
route.

Rick


Richard Crisp wrote:
it says composite but composite can mean different things to different
people

it can be a composite made from different filters....

the abg camera makes is far more doable than an NABG in my opinion

deeper wells help too.

my sensor used was the KAF6303E.... 100K wells NABG


"Rick Johnson" wrote in message
...

As Stefan and Richard mention this is the Cat's Eye Nebula NGC 6543. The
bright blue part of it to the right is IC 4677. The Cat's Eye nebula is
about 3000 light years away. There are two famous Hubble shots of it:
http://antwrp.gsfc.nasa.gov/apod/ap061112.html
http://apod.nasa.gov/apod/ap070513.html

A composite of the eye and the distant faint shell I shot, as Richard
wants to avoid, taken by earth based scopes is at:
http://apod.nasa.gov/apod/ap020904.html

If I ever get super seeing, I'll try a similar compost. To do it in one
shot isn't possible with an ABG camera like mine. With a long enough
exposure to capture the outer shell the inner part is reduced to a handful
of intensity levels by the ABG gate. In my shot the core was 57126 to
57214 ADU units showing no useful detail.

The galaxy is NGC 6552 and is some 325 to 350 million light years distant.
For it to appear this large at that distance it is a giant galaxy!

Rick