Hi PGC & All,
Quote:
Originally Posted by pgc hunter
G'day Les,
So I wasn't the only one surprised by the brightness of that ESO group! I totally share your sentiments, these galaxies are better than many NGC objects. Some of these more obscure catalogues certainly do hold some pleasant surprises. I'll have to revisit this group after cleaning my mirror!
Btw Les, where do you get your galaxy magnitudes from?
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Galaxy magnitudes (not so much the bright ones -- say brighter than 11th mag) are, put succinctly, somewhat of a pigs breakfast. You've got to think of the supplied magnitudes in many cases as being a bit like the "pirate's code" -- its more of a guide ... The "fainter" they are the worse it gets. Some are photometry at some strange passband, some are estimates and others are guesses based on their appearance in a survey plate. Most faint galaxies have not had accurate photometry. Those that have, it is infrequently a visual pass-band.
The ones in my little reports generally (almost always) are the ones from Megastar. They are often inaccurate or just plain old and out of date. When I make my log entry in Deep Sky (database software), I click on the text box containing this info in Megastar and place it in the field where the general comments go, before the description. I don't strictly need to because Deep Sky supplies all that info -- but that only works when looking at the log entry in Deep Sky. The magnitude in Deep Sky is not infrequently different from Megastar -- particularly the faint ones.
If I ever want to convert the comments in my log into a word doc it's easier to have it in that field -- just cut and paste and you've got
something there at least.
The galaxy magnitudes provided by Megastar generally come from several sources. Some reliable, others not quite so reliable. Most of the brighter ones come from the RC3 (3rd Revised Catalogue of Galaxies), some come from the PGC (Principal Catalogue of Galaxies) from 1989 (one assumes you are familiar with that catalogue
) and others from the old CGCG (Catalogue of Galaxies and Clusters of Galaxies) compiled by Fred Zwicky in the 1960's. On the other hand the PNe magnitudes are pretty recent and quite reliable. GC magnitudes are aanother pigs breakfast and are derived from a whole mish-mash of sources.
If I'm going to use a magnitude for a "critical purpose" -- ie publication etc I'll check it with NED or the NGC/IC project (assuming it is an NGC) and if there is a variance, I'll go with my "best pick" from NED.
Yep there is a lot of stuff outside the NGC (particularly in the southern hemisphere) that is quite bright and nice to look at. ESO 240-11, if it were in the northern hemisphere would be a "large 'scope showpiece". Obviously not good for small telescopes but in 12" and larger it is really beautiful. For those who like their galaxies faint and as skinny as Gandhi on a diet, (off the top of my head), take a look at IC 2531 in Antlia, NGC 7064 in Indus and for a real 12" challenge IC 5249 in Tucana ... Yum
Best,
Les D
P.S now that gives me an idea ...