Re: [APML] 10 frame Rosette Mosaic

[Philip Perkins <philip@astrocruise.com>]

Hello Bobby,

That's a wonderful result and a deserved reward from what was obviously a 
large amount of effort.  I was impressed by the rather good colour of the 
Ha regions in your shot - that must be entirely due to your hypering since 
the normal LE 400 response would have tilted it towards the dreaded 
orange-red <g>.  I suppose the big mosaic is because you can't get your 
hands on a decent 120 format film?  The interesting thing is that you can 
cover the entire Rosette region on 120 format with your 12.5" by using the 
AP focal reducer. I did exactly this using my 12.5" from southern France in 
December.  I took four frames and each one is a winner in terms of focus 
and guiding accuracy.  I just haven't got round to scanning the negs yet - 
frankly I'm a bit nervous about the result because this is from the same 
outdated PPF stock that I had previously declared "duff".  However the 
nebulosity shows clearly on the negs - perhaps I should at least give it a 
try.  The full frame 6x7 format gives me 112Mb files when scanned on my 
Sprintscan 45 Ultra though this has to be cropped down somewhat in the case 
of the RC owing to the vignetted circle I get from using the RC with 2.7" 
focuser parts.  I get the full 6x7 field evenly illuminated when using the 
AP 155 with 4" focuser.  I have to say that the 120 format situation is 
pretty dire at the moment...

--Philip


At 13:15 10/02/02 -0600, you wrote:
>Hello all. I've finally posted my "winter project" for this season. It's a
>10 frame (yep; ten) mosaic of the Rosette nebula. I was able to oevrcome the
>frame warping difficulties that kept me from going past 5 or 6 frames on my
>previous projects by registering the central 3-4 frames with Registar on top
>of a wide-field image; then building the additional single frames on top of
>that. I still had some warping but I believe one can take the image at
>whatever stage and re-register it on a widefield image to get things back to
>linear alignment. It's here:
>http://www.koyote.com/users/bobm/rosette2.htm
>All 10 frames are composites of two 60 min exposures on hypered Kodak LE 400
>film.
>I posted a high-res crop of this to the AP users group about 2 weeks ago for
>comparison with CCD images made with two different wide-field instruments.
>The high-res central crop from my 12.5" f/7 newt is on the page below along
>with an identical crop from Ray Gralak's AP 105 st-8 Ha image and Mark
>Jenkin's Ha image from a 9.25" Mak-newt with a FLI CCD camera. Those
>comparisons are at the link below if anyone is interested in resolution
>comparisons of film and CCD cameras. The fewer stars from the CCD images are
>a result of the Ha filter.
>http://www.bigcigarastronomy.com/Rosette-Comparison2.jpg
>Bobby Middleton
>
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Philip Perkins - philip@astrocruise.com
Wiltshire UK & Luberon France
Astrocruise - http://www.astrocruise.com


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