IMAGE POSTING: Markarian's Chain in VirgoThese are wonderful images.
Detailed, careful... "all carried on a ...mount unguided." Wow. Short
exposure CCDs merged in software? Lynne.
-----Original Message-----
From: sf-bay-tac-bounces@No-Spam [mailto:sf-bay-tac-bounces@No-Spam]On
Behalf Of Paul LeFevre
Sent: Tuesday, April 01, 2003 7:02 AM
To: Sf-Bay-Tac (E-mail)
Subject: [TAC] IMAGE POSTING: Markarian's Chain in Virgo
Saturday night was very clear and dry down here near San Diego, but quite
windy...
I gave up trying to image at long focal lengths because of the wind, and
instead started a wide-field image appropriate to Galaxy season.
The image is of the portion of Markarian's Chain in Virgo, just poking
into Coma a bit (with NGC 4473).
I used my little Takahashi FS60C with a focal reducer for a 264mm focal
length, a StarlightXpress HX916 camera, and 38 minutes of exposure
unfiltered (I shot 60 minutes, but had to throw away a few 'cause of
windblown trailed stars!), piggybacked on a C8 SCT, all carried on an
AP900GTO mount unguided.
(the images are 1300x1030 in size, and about 175k)
http://www.lefevre.darkhorizons.org/ccdimaging/mkchn1.jpg straight image
http://www.lefevre.darkhorizons.org/ccdimaging/mkchn1lb.jpg labeled
version
(North is down in the images)
I'm amazed at how deep the image goes for just 38 minutes exposure. The
faintest galaxies I can easily pick out are mag 16.4, and the faintest star
I can positively identify is mag 21.3. If I hadn't been shooting into my
southern light-pollution gradient from my backyard, and had to throw away 22
minutes, it would probably be much deeper. It's quite fun to shoot an image
like this, then track down all the visible objects. Incidentally, in making
the labelled version, I had to check multiple references because of some
conflicting positions -- in the process, I verified that the Coma/Virgo
cluster charts in the Spring "Night Sky Observer's Guide" (specifically page
94, Volume 2) have a number of mis-named NGC and IC galaxies. The labels on
the image are as correct as I can be sure of, verified through The Sky and
SkyMap Pro along with some Palomar Sky Survey images from the web. The NSOG
were generated with a version of MegaStar (it doesn't say which one), which
leads me to believe that MegaStar must also have some mis-named galaxies in
the region.
I'm going to make the image negative (makes it easier to discern really
faint stuff) and try to chase down some of the really faint galaxies in the
image. I'll post up that version later if anyone's interested.
Paul
