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calan
sage
Reged: 06/16/07
Posts: 245
Loc: Oklahoma City, OK
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I'm looking for a list of the most easily seen galaxies. The problem is (as you probably know), this doesn't necessarily relate to their brightness or magnitude.
For example, last night I was lazily pointing my dob at different parts of the sky around 2:00am, and just for giggles decided to look for an object on my list, NGC7331. I mistakenly thought I was going to be looking for a PN (read the symbol in Planetarium wrong  ). Was I ever surprised when right there only a few degrees from a glaring moon, I'm looking at a galaxy! A few checks of corrdinates and the map, and sure enough I've got NGC7331 visible in my EP, moon/LP skies and all; in fact, the moon and LP were actually washing out stars in that area that would have been visible otherwise. It was almost as easily seen as M31, and was actually quite a bit easier than M51 was earlier with no moon in a much darker part of the sky.
Looking at various lists around (like this one for example), NGC7331 shows up at the bottom or not at all, while other much fainter ones show up nearer the top. (I'm talking about those I've seen organized by relative brightness here).
So...
Is there a good list anywhere that is based on how easy it is to actually view these faint cotton balls, rather than by magnitude, SB, and other generally useless info? 
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Orion XT10 (completely rebuilt, DOB or GEM mountable)
Meade LXD75 6" Newt w/mods
Nikon 10x50 AE Extreme
Hyperion 21mm and 8-24mm Zoom
Astrotech 38mm Titan II
BO/TMB 6mm
Various Plossls
Time flies like an arrow, but fruit flies like a bannana.
The trouble with most jobs is the job holder's resemblence to being one of a sled dog team. No one gets a change of scenery except the lead dog.
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AlanK
super member
Reged: 01/26/07
Posts: 128
Loc: Auckland, New Zealand
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Rather than a list, something such as the Night Sky Observers Guide from Willmann-Bell would be better as it covers all the showpiece and some fainter objects along with observations through different apertures - which would give you a much better idea on object visibility.
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12.5 inch f5.4 reflector
18 inch f4.5 Obsession #1637
Auckland NZ
5,984 deep sky objects incl 4,236 ngcs.
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Josh U
member
Reged: 07/10/07
Posts: 41
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I really like the Steve O'Mera books. (Of course, his scale of brightness has M31 ready to light up the superbowl!) Well written, and fantastic field references. Some cool stuff! I've got the Night Sky Observer's Guide, but I like Steve's stuff a lot better. "Hidden Treasures" is a nifty volume.
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"How you do anything is how you do everything."
Zhumell 10" dob
80mm Refractor
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BillFerris
Carpal Tunnel
Reged: 07/17/04
Posts: 2576
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If you sort galaxies in ascending order by integrated visual magnitude, you'll find the ranking fairly accurate with respect to relative visibility. By contrast, surface brightness does a relatively poor job as a lone determinant of visibility. For instance, NGC 7331 ranks 44th in integrated magnitude (tied with NGC 147 and NGC 3628) on the list of galaxies I've observed and sketched. However, it's 22.1 magnitude per square arcsecond surface brightness is about the same as showpiece objects PGC 50133
and HCG 80D.
Bill in Flag
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Grand Canyon Adventure
Lowering the Threshold
18" Obsession
4.5" Meade 4500
10x50 Swift Audubon
Cosmic Voyage
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calan
sage
Reged: 06/16/07
Posts: 245
Loc: Oklahoma City, OK
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Bill,
That is exactly what I'm looking for...do you have a list compiled showing/sorted by the integrated visual mag?
I'm putting together a list for some kiddos, and when they say "I wanna see some galaxies", I want to have an idea if they'll actually see them...and unfortunately I don't have time to go hunt down a hundred galaxies to get maybe 10 that would make the list 
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Orion XT10 (completely rebuilt, DOB or GEM mountable)
Meade LXD75 6" Newt w/mods
Nikon 10x50 AE Extreme
Hyperion 21mm and 8-24mm Zoom
Astrotech 38mm Titan II
BO/TMB 6mm
Various Plossls
Time flies like an arrow, but fruit flies like a bannana.
The trouble with most jobs is the job holder's resemblence to being one of a sled dog team. No one gets a change of scenery except the lead dog.
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BillFerris
Carpal Tunnel
Reged: 07/17/04
Posts: 2576
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Here's a link to a list I posted a couple of years ago: Galaxy Visibility.
I played with a number of different formulas to calculate a "Visibility Index" and ended up going with the most simple: V Index = (Mag + SB) - 30
I subtracted 30 from the sum of integrated magnitude and surface brightness so the resulting numbers would fall within a range that amateur astronomers know quite well; from the magnitudes of the brightest planets in the night sky to those of the faintest stars visible to the naked eye and beyond.
My ordering certainly isn't the last word on the subject but it does well enough for my purposes.
Bill in Flag
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Grand Canyon Adventure
Lowering the Threshold
18" Obsession
4.5" Meade 4500
10x50 Swift Audubon
Cosmic Voyage
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VanJan
super member
Reged: 07/09/08
Posts: 111
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Many years ago, in one of Alan MacRobert's star-hops in S&T(Virgo Cluster one, I believe, not in his book) he gave a Visibility Index formula that was as simple as yours but somewhat different - if I am recalling correctly, which is always a question. Seemed to work well for his 6" through the Virgo Cluster. Are you familiar with this Visibility Index formula, and, if so, your opinion of it, please. Thanks!
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calan
sage
Reged: 06/16/07
Posts: 245
Loc: Oklahoma City, OK
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Very cool Bill.
Do you happen to have an Excel version of this?
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Orion XT10 (completely rebuilt, DOB or GEM mountable)
Meade LXD75 6" Newt w/mods
Nikon 10x50 AE Extreme
Hyperion 21mm and 8-24mm Zoom
Astrotech 38mm Titan II
BO/TMB 6mm
Various Plossls
Time flies like an arrow, but fruit flies like a bannana.
The trouble with most jobs is the job holder's resemblence to being one of a sled dog team. No one gets a change of scenery except the lead dog.
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FirstSight
Carpal Tunnel
Reged: 12/26/05
Posts: 2512
Loc: Raleigh, NC
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Yes, galaxies are typically rated in terms of both integrated brightness and surface area brightness, independent of atmospheric conditions and what instrument is being used to attempt to view them.
Nevertheless, one informal, but revealing test of which galaxies are "bright" in a practical observing sense is to compare which ones are findable, and with what difficulty, in a smaller e.g. 80 or 90mm refractor rather than a 10" or 12" light bucket, against what general sorts of viewing conditions. Owners of 12" dobsonian light buckets tend to think of M51 as one of the easier "bright" galaxies to view under all but egregiously light polluted skies (even if any more detail than twin smudges is washed out), but M51 can be one tough bugger to track down against any significant degree of light pollution in a 90mm refractor, despite having what seems like it should be an easy location to accurately track down relative to other bright objects. OTOH, M81/82 are second only to M31 for being still readily findable/viewable in small refractors under surprisingly tough conditions of transparency/light pollution.
Under my average-sort of suburban skies, NGC7331 jumps immediately and prominently out in my 12" dob when within the field of view, and is findable on nights of good transparency in my 90mm refractor, but can require some patient study in the latter scope before it begins to become faintly, but distinctly apparent against the surrounding background.
M101 and M33 are two particularly maddening cases - observers who often enjoy fairly dark, transparent skies speak of how obvious these two are to find and view, even in binoculars (true, I've seen this for myself under appropriate conditions in both binoculars and my 90mm refractor) - but so quickly fade like the Cheshire Cat into invisibility against any significant degradation of atmospheric conditions, including modest suburban light pollution, in even a 12" light bucket.
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Chris M., aka "First Sight"
Orion XT12i Dob with Moonlite CR-2 focuser
WO Megrez 90 refractor on UniStar Light mount
Nikon 10x50 Binoculars
Edited by FirstSight (07/24/08 03:50 PM)
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calan
sage
Reged: 06/16/07
Posts: 245
Loc: Oklahoma City, OK
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Yep...I'll agree with the M51 comment. As stated, 7331 jumped right out at me, and it was only a few dgrees from the moon about 45* up. M-51 was slightly past zenith in relatively "dark(er)" skies, but not nearly as easily seen. Doesn't seem to be possible, but it happened.
I looked a bit later to make sure it wasn't different dark adaptation, different eyepieces, etc., and it was the same results.
--------------------
Orion XT10 (completely rebuilt, DOB or GEM mountable)
Meade LXD75 6" Newt w/mods
Nikon 10x50 AE Extreme
Hyperion 21mm and 8-24mm Zoom
Astrotech 38mm Titan II
BO/TMB 6mm
Various Plossls
Time flies like an arrow, but fruit flies like a bannana.
The trouble with most jobs is the job holder's resemblence to being one of a sled dog team. No one gets a change of scenery except the lead dog.
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Ptarmigan
Carpal Tunnel
Reged: 09/23/04
Posts: 1873
Loc: Arctic
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The only galaxy I can see in a light polluted sky is M31, M32, and M110 if conditions are perfect. I can only see M33 in a dark sky.
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Ptarmigans=Cute and Cuddly
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Tony Flanders
Carpal Tunnel
Reged: 05/18/06
Posts: 2053
Loc: Cambridge, MA, USA
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Quote:
If you sort galaxies in ascending order by integrated visual magnitude, you'll find the ranking fairly accurate with respect to relative visibility.
I agree, but with two important provisos. Integrated magnitude is by far the best predictor of visibility if you are an experienced galaxy observer and you habitually view under dark skies. Inexperience and light pollution both dramatically increase the importance of surface brightness as compared to integrated brightness.
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Tony Flanders
eyeglasses
6x15 and 8x32 monoculars
8x25, 7x35, 10x30 IS, 10x50, and 15x70 binoculars
70mm and 100mm achromatic refractors
4.5", 7", and 12.5" Dobs
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