Re: [APML] OT: Comet Neat on May 15

[Philip Perkins <pgp@astrocruise.com>]

Chris, Stuart, Jeff - thanks very much for your comments.

Yes, there are quite a few shots showing the comet without trailed stars 
and I think several techniques have been used to do this - one of which, as 
you say is to re-shoot the field without the comet.  Actually the star 
trails are very easy to remove anyway using the healing brush in PS 7.  The 
way this works is almost 'magical' - it removes the star trail completely 
while preserving all the structure underneath the trail.  I did this with 
the RGB image before compositing it with the luminance image to avoid RGB 
'traffic lights' being scattered all over the image :)  It would also have 
been easy to remove them from the luminance image, but I felt this would be 
'doctoring' the image a bit too far.  The stars are real enough and part of 
the image, and also help convey just how rapidly the comet is moving 
amongst the stars.  The downside is that the stars are luminance only.

Another time I would use longer exposures - the idea of the short exposures 
was to preserve detail into the nucleus, but I think that 20 or 30 seconds 
per exposure would have got the same result with more detail in the tail 
and less noise in the image.

Thanks
--Philip

At 17:03 16/05/2004 -0400, you wrote:
>Philip - that is a really unusual photo, the comet really shows its form
>when you guide on it. You got a great photo with such short exposures.
>
>Someone was hinting at removing the stars in a shot guided on the comet
>nucleus and then reshooting the same field without the comet and
>stacking them. Your shot would look to make that pretty easy. The number
>of stars you'd have to remove would not be that many. Maybe cheating but
>it would look amazing. Worth a try, not sure it is kosher though. Like
>you need more work. It's beyond me at my skill level but with a photo
>like that it would be tempting.
>
>Stuart
>http://www3.sympatico.ca/stuart.j.heggie/Stuart.J.Heggie/
>Flesherton, Ontario, Canada

>Phil,
>That is a very pleasing shot.  I know others like to fix the comet
>against the star field, but my thoughts are that we rarely can depict
>motion in a still photograph of an astronomical object and comets are
>one of those special times.  I like the stars trailing as it adds a
>feeling of movement and when the stars are done well (well focused and
>no guiding errors as in your shot) it really adds to the shot.  Very
>nicely done and thanks for posting.
>
>Best regards,
>Jeff Ball
>www.astro-photography.com
>

Philip Perkins
<pgp@astrocruise.com>
Wiltshire UK & Luberon France
http://www.astrocruise.com

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