M 102* (NGC 5866, UGC 9723) Galaxy in Draco

Located at: RA 15 hours 06 minutes 29 seconds, Dec +55 degrees 45 minutes 48 seconds

Size: 6.4' x 2.8' Magnitude: 10.7 blue Class: SA0+ sp (S0_3 HII)**

North is up

West to the right


 14.5" f5 Newtonian reflector


 ST-8XME, self-guided, binned 1x1, temp -15c & -20c, camera control MaxIm DL 4.56


Lumicon Red filter, 490 minutes (49 x 10 minute subs), 05/18/19/20/2013; seeing 2.8-4.3 FWHM per CCDStack


CCDStack 2.69.4870.18821, Photoshop CS5.1


 Rolling Roof Observatory, Thousand Oaks, CA 91360 (+34d 13m 29s -118h 52m 20s)


I am listing the "M 102" prefix first ... but this object should probably be called NGC 5866! The 'real' M 102 designation is possibly a re-observation of M 101. See the 8" version.

Refer to data for M 101 and M 102 at The NGC / IC Project:

Contemporary Visual Observation(s) for NGC 5866

NGC 5866 = UGC 09723 = MCG +09-25-017 = CGCG 274-016 = LGG 396-001 = PGC 53933
15 06 29.3 +55 45 49
V = 9.9;  Size 4.7x1.9;  SB = 12.2;  PA = 128d

17.5": very bright, fairly large, elongated 2:1 NW-SE, 3.0'x1.5', bulging bright 
core.  This galaxy has a high surface brightness and a mottled surface.  Just a 
hint of the razor-thin dust lane prominent on photographs is visible.  A mag 
11.5 star is at the NW end 1.6' from the center and a slightly fainter mag 12 
star is 1.5' SW.  Located 10' NE of mag 7.5 SAO 29401.

13": very bright, impressive, large bright core, two stars off the NW and SW 
edges.  A mag 7 star is 10' SW.

- by Steve Gottlieb
Historical Research Notes / Correction for NGC 5866
NGC 5866 is not Messier 102, though there is a long history of taking this 
galaxy to be one of those found by Mechain (in 1781 in this case), and 
included by Messier in his 1781 list.  For M102, however, Messier did not have 
time to visually verify the object, so his "work" on it is limited to a 
penciled-in position in his own copy of his list published in Connaissance des 
Temps for 1783/4.  That position is "14.40" and "56", i.e. 14h 40m, +56d.  
There is no equinox given, but we can assume it to be 1780 without too much 
error.  For comparison, the accurate position for N5866 precesses back to 
15 00.5, +56 37 for 1780.  For M101 (= NGC 5457, which see), the actual M102, 
the precessed accurate position is 13 55.4, +55 25.

It's clear than neither galaxy fits the written-in position in Messier's list.
But some evidence in favor of NGC 5866 has been found.  This has been 
collected in a Web document by Hartmut Frommert on the SEDS site:  


To summarize Hartmut's case for NGC 5866:  Messier's working maps were laid 
out in grids of five degrees in both RA and Dec.  This makes it possible that 
the written-in position was hastily read off his map with a 20 minute and 1 
degree error for "15.00" and "57"; this would make the object NGC 5866.  

However, Steve O'Meara points out in his "Eye on the Sky" column for the March
2005 issue of "Sky and Telescope" that the incorrect position is about as far 
east of theta Bootis as M101 is west.  It seems more likely then that Messier 
made a simple plotting mistake, flipping the offset from theta Bootis, and 
therefore wrote down the incorrect position because of that.  I think it is
worth pointing out here that the same kind of mistake may possibly account for 
Messier's poor position for M47 (= NGC 2478).

The case for M102 being M101 is made virtually certain by a letter that 
Mechain wrote in 1783 to the editor of the Berliner Jahrbuch.  In it he says
that the entry for No. 102 is nothing more than a repeated observation of 
M101, included in Messier's list due to his (Messier's) confusion over the 
position.  The German translation of this letter was published in the Jahrbuch
for 1786.  This still exists and was reprinted in 1947 by Helen Sawyer Hogg;
I've copied it into the note for M101 (= NGC 5457, which see).  

The letter was, however, pointed to as early as 1877 by Edward Holden in his 
"Index Catalogue of Books and Memoirs Relating to Nebulae and Clusters."  
Bigourdan also discusses this in the Introduction to his extensive 

Also see Steve O'Meara's article for a thorough discussion of M102 and its 
true identity.  Much of what I've had to say here and in the note for N5457 is
abstracted from his article.

On a different puzzle, see NGC 5826 where Swift has confused NGC 5866 with 
another galaxy, and NGC 5867 where N5866 helps in the identity of that object.
 - Dr. Harold G. Corwin, Jr.

* and/or: *                   

Refer to the SED's site for the case for it being NGC 5866

** NED Classification