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chornedsnorkack
2011-Mar-02, 08:18 PM
Listing the objects brighter than +6,0:

Messier objects (northern sky):

M6 - quoted as +4,5 and +4,2
M7 - quoted as +3,5 and +3,3
M8 - +6,0
M13 - +5,8
M16 - quoted as +6,5 and +6,0
M17 - +6,0
M22 - quoted as +5,1 and +5,5
M23 - quoted as +6,0 and +6,9
M24 - +4,6
M25 - quoted as +4,9 and +4,6
M31 - +3,4
M33 - +5,7
M34 - quoted as +6,0 and +5,5
M35 - quoted as +5,5 and +5,3
M37 - quoted as +6,0 and +6,2
M39 - +5,5
M41 - +4,5
M42 - +4,0
M44 - +3,7
M45 - +1,6
M47 - quoted as +4,5 and +4,2
M48 - +5,5
M50 - quoted as +7,0 and +5,9
M93 - quoted as +6,5 and +6,0

NGC southern sky objects:

NGC104 - quoted as +5,8, +4,9 and +4,0
NGC292 - quoted as +2,8 and +2,7
NGC869 - quoted as +5,7 and +5,3
NGC1499 - quoted as +4,1 and +6,0
NGC1788 - quoted as +5,8 and +9,0
NGC2169 - quoted as +6,0 and +5,9
NGC2244 - quoted as +5,3 and +4,8
NGC2264 - +3,9
NGC2362 - +4,1
NGC2516 - +3,8
NGC2547 - +4,7
NGC3293 - quoted as +4,8 and +4,7
NGC3532 - +3,3
NGC3766 - quoted as +5,7 and +5,3
NGC4755 - +4,2
NGC5139 - quoted as +6,1 and +3,7
NGC6025 - +5,1
NGC6087 - quoted as +5,9 and +5,4
NGC6124 - +5,8
NGC6193 - quoted as +5,3 and +5,2
NGC6231 - quoted as +2,8 and +2,6
NGC6633 - quoted as +5,0 and +4,6
NGC6752 - quoted as +7,0 and +5,4

So, which nebulae in this list are visible to naked eye?

Hornblower
2011-Mar-02, 11:18 PM
I have seen M13 with averted vision near the zenith, on a night when I could see stars as faint as 6.2 or 6.3. With M33, about the same total magnitude but more diffuse, I have never had any such luck, though it is easy in 7x50 binoculars in a dark sky. M31 and M42 are easy naked eye objects in a dark sky.

ngc3314
2011-Mar-03, 01:21 AM
From personal experience, M6,7,8,13,31,33,42,44,45. Of those M33 is much the most demanding of sky conditions. NGC 104, 5139, 869 (which is one of the Double Cluster members in Perseus rather than being southern). I stipulate that I haven't looked for all of them naked-eye. (My inner pedant is whispering that most of these are star clusters rather than actual nebulae...)

chornedsnorkack
2011-Mar-03, 10:47 AM
From personal experience, M6,7,8,13,31,33,42,44,45. Of those M33 is much the most demanding of sky conditions. NGC 104, 5139, 869 (which is one of the Double Cluster members in Perseus rather than being southern).
Yes, it is odd that although Double Cluster is conspicuous in northern sky (quoted as bright as +4,2) and always known, it is not a M.


I stipulate that I haven't looked for all of them naked-eye. (My inner pedant is whispering that most of these are star clusters rather than actual nebulae...)

Notoriously so with M45, which is why it is odd that it is M. At total magnitude +1,6, a brightest member at +2,86 and 6 members brighter than +4,29 (the total number and names of members brighter than, say, +6,0 has proven hard to find), it is not a visible nebula.

Whereas M44 is a nebula: with brightest member quoted from +6,3 to +6,6 yet total brightness quoted from +3,1 to +3,7, it can be seen but not resolved.

Hornblower
2011-Mar-03, 11:10 AM
I don't have the foggiest idea why Messier included the Pleiades in his list, but not the Double Cluster. I cannot see mistaking the Pleiades for a comet.

At the risk of sounding pedantic, let me remind everyone that M44 is not a nebula, though it can pass for one to the unaided eye.

George
2011-Mar-03, 06:01 PM
FWIW, though all here likely know this, since galaxies were not established by then, Messier's original catalog (http://messier.obspm.fr/xtra/history/m-cat71.html) of 1771 was entitled "Nebulae and Star Clusters", though this was only the first 45 objects. He mentions naked eye viewing of M6, M7, M42 and M44.

chornedsnorkack
2011-Mar-05, 08:38 AM
I have seen M13 with averted vision near the zenith, on a night when I could see stars as faint as 6.2 or 6.3. With M33, about the same total magnitude but more diffuse, I have never had any such luck, though it is easy in 7x50 binoculars in a dark sky.

Both are magnitude 5,7...5,8.

M13 is about 20...23 arc minutes across (hazy edges). M33 is quoted as 71x42 arc minutes.

Under 4x magnification, M33 would be +2,7...+2,8, and extend 284x168 arc minutes. NGC292 is +2,7..+2,8, and extends 320x185 arc minutes. It is notorious for low surface luminosity - yet plainly visible, even Vespucci immediately saw two Magellanic Clouds, not one.

Which is actually easier to see - NGC292 or NGC104?

chornedsnorkack
2012-Feb-04, 11:51 AM
Sorting out just the objects which have been quoted at above +5,0:
M6
M7
M24
M25
M31
M41
M42
M44
M45
M47

NGC104
NGC292
NGC1499
NGC2244
NGC2264
NGC2362
NGC2516
NGC2547
NGC3293
NGC3532
NGC4755
NGC5139
NGC6231
NGC6633
Brighter than +3:
M45 - +1,6
NGC292 - +2,7 or +2,8
NGC6231 - +2,6 or +2,8.
Why is NGC292 in NGC? Large Magellanic Cloud is not.