[APML] Comet Ikeya-Zhang from 2002-04-04

[Roland Roberts <roland@astrofoto.org>]

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I finally went back and processed this image from last year.  The
originals were, well "yucky" is about the best I can say for them.  I
was still using Fuji Superia ISO 800 for "short" shots under 10
minutes and it hadn't completely sunk in how bad the color shift
toward cyan was.  I've stacked 6 images with exposure from 1 to 4
minutes.  I've got some artifacts caused by bad level matching that
require me to go back and do a better job cropping before compositing,
but the comet is visible and M31 is also slightly visible.

        http://www.astrofoto.org/gallery/solar/comets/c2002-c1.html

The biggest accomplishment of this photo is that there is anything at
all to look at :-) The sky was too bright for the exposure times I
used (don't be fooled by how dark it looks, I've cheated to enhance
the comet), the film image was mostly cyan (I messed with the color
balance a lot get get something more blue than pukey green), I
more-or-less skipped the polar alignment because I arrive late after
dark and just pointed at the pole.

To enhance the comet and darken the sky, I did the same thing I would
have done for gradient removal, I did a large (100-pixel diameter)
Gaussian blur and subtracted a fraction of it out of the original
image (in this case, about 67%).

Anyway, I've seen a *lot* better shots put up by people here, but
hopefully this will encourage other newbies that there is hope, even
when things don't go very well (bad film, bad exposure, late arrival,
hasty set up).

regards,

roland
- -- 
		       PGP Key ID: 66 BC 3B CD
Roland B. Roberts, PhD                             RL Enterprises
roland@rlenter.com                            6818 Madeline Court
roland@astrofoto.org                           Brooklyn, NY 11220

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