On 4/20/2010 11:08 AM, Glen Youman wrote:
Now you've got me concerned - I don't believe it is an artifact but I
can't nail it down - the Poss plates aren't that deep - I'll keep
looking.
On Mon, 19 Apr 2010 14:13:02 -0500, Rick
wrote:
On 4/19/2010 12:25 AM, Glen Youman wrote:
I'm puzzled by the detached piece to the lower left. I didn't pick it
up in my image from 2007.
http://www.spacebanter.com/attachmen...ntid=971&stc=1 For
some reason I see I only used 3 ten minute Lum subs so not as deep as
I'd like. Still I think it should show but doesn't.
I stretched the blue POSS II plate and can't find it there either. I
wonder if it is a processing artifact or a ghost image. The rest looks
great.
Rick
I tried a super nasty hard stretch of the SDSS image (attached). It is
severely clipped in blue but not red or green. I see no hint of
anything in that location.
NGC 4399 is the star cloud almost directly opposite the detached piece
in question, not far from a slightly orange star in your image. It is
well within the halo of the galaxy.
I've had internal reflections make such an object. I was sure it was
real but before I finished processing the image I retook it and there it
was. So now I was sure it was real. But then I realized I was using
the same centering as before within a pixel or so. So I moved
everything one minute of arc and tried again. It was gone! No sign of
it. I never did find a suspect for it. No bright star nearby at all.
Since then I've had it happen twice more. Those times I trusted Sloan
and the DSS plates stretched hard and just cloned them out. Later when
they were back in the sky again a test frame showed I was right doing
so. Whew!
Rick
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