[APML] OT? Markarian's Chain and printing

[<apml@beskeen.com>]

Hi,

Not entirely sure if DSLR images are welcome here, but I guess there's one
sure way to find out :)

Markarian's Chain isn't exactly a rare image and the composition of this
shot isn't the best, but not too bad. I would appreciate any general
comments on how I could improve the processing of the shot, but I'm
particularly interested in comments on how best to print the image. I
printed direct from photoshop on my printer (a Canon S9000 - a reasonably
high-end photoprinter), and I loose a lot of the fine wispy detail
(especially in NGC4438/NGC4435 interacting? pair) that I can see on the
monitor. Overall the image looks a little too dark when printed. I have not
used any color matching calibration, but I'm not sure that that would help
in this particular problem anyway. I know its difficult to diagnose an print
that none of you can see, but maybe this is a relatively frequent issue that
people hit? Do folks generally have a different processing for a printed
shot as apposed for a shot for on-screen display? Are there standard tricks
to calibrate the monitor and printer to get comparable results - is this
part and parcel of the color matching s/w?

Canon 300D 10x5min ISO800, temp 4C.
http://www.beskeen.com/astro/dso/MarkariansChain-10x5m-avedark-avecmb-dd1614-avin.jpg
For grins I also labeled the main galaxies and a smattering of the very
faint fuzzies. I got down to around magnitude 18 galaxies before the noise
defeated the signal, couldn't see any of the mag 19s that were the limit
shown in my atlas. There appears to be hundreds of galaxies in the shot if
you peer down into the pixels. Best to zoom in to around 200-300x. At the
high magnitudes it gets difficult to determine whats noise, faint stars or
real galaxies without using an atlas :-/ Wouldn't have harmed having a
couple more hours data to improve the s/n and go deeper...
http://www.beskeen.com/astro/dso/MarkariansChain-10x5m-avedark-avecmb-dd1614-avin-txt.jpg
[Error in the labelling - I have two NGC4438's... The northern of the two in
teracting galaxies should be NGC4435]

My image processing has improved somewhat from my earlier attempts - part of
the processing was the use of a technique out of Jerry Lodriguss's excellent
book "Photoshop for Astrophotographers" http://www.astropix.com/PFA/PFA.HTM
a strong median filter blurring of the image to remove the stars, then the
clone tool to replace the smudged large galaxies with similar background,
and then subtraction of this from the original. This removed the vignetting,
colour imbalance and light pollution gradients - pretty cool technique -
useless if there is any nebulosity in the picture mind. Everything else was
done with ImagesPlus - preprocessing included dark frame calib 10x5 average
master dark, averaged the 10x5 light frames, and finally an application of
ImagePlus's digital development (curves for the impatient).

Cheers, Paul.
--
Canon 300D 10x5 min exposures at ISO800. Borg 101ED at F5.4, piggybacked on
LX200, guided by STV. IDAS LPS filter. Long exposure control via DSLRFocus
and serial cable.
http://www.beskeen.com/astro/SerialDSLRControl/SerialPortControlCables.html


_______________________________________________
Astro-Photo mailing list
Astro-Photo@seds.org
http://seds.org/mailman/listinfo/astro-photo