[AZ-Observing] Re: M33 faint limits
- From: Brian Skiff <bas@xxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Thu, 08 Nov 2018 16:08:31 -0700
On Thu, 2018-11-08 at 15:37 -0700, Albert Barr wrote:
Brian the blacks are definitely not clipped. I always check for that. I
pulled it up and stretched it hard and I can’t really get much more out of
it. I also looked at an APOD of this galaxy and the arms don’t go out much
more than mine, if at all.
So your image goes out to about 1.1 or 1.2 degrees length
on the major axis, which I measured by comparing it with the
scan of the POSS-II blue plate. The plot of M33's surface
brightness here:
http://astronomy.nmsu.edu/aklypin/AST616/SpiralSurf.pdf
...about 1/3 the way down this set of lecture notes, shows the
surface brightness at that size is about mag 25 per square
arcsecond. M33's disc is indeed truncated, so after that
the brightness drops off quickly. But with a 10- or 12-inch
telescope from a dark site you can _see_ mag 25/square arcsec
_visually_, so it seems like a stack of umpteen hours of
images would go a lot fainter (26? 27?). But evidently not!
You might need really first-class flat-fields and bring up
the sky background to a level unacceptable for artistic purposes
(the main part of the galaxy totally washed out), but I still
think there's more information in here than you're letting on.
\Brian
--
See message header for info on list archives or unsubscribing, and please
send personal replies to the author, not the list.
Other related posts:
