Extragalactic Globulars

The Brightest Globular Cluster in Eight Nearby Galaxies

You might wonder why anybody in his right mind would spend hours searching for something that looks just like another field star, and a damn faint one at that. Well, we all enjoy looking at Pluto, don't we? Why? Just because it is Pluto, I guess. Likewise with quasars; it is cool to find something that is so far away! Globular clusters in other galaxies are like that. They are not much to look at, but it is pretty neat to track down a certain pinpoint of light and realize that it is actually a swarm of thousands of stars comparable to M13 or Omega Centauri in our own galaxy, but immensely further away! It helps, I guess, if you are the kind of deep sky observer who enjoys tackling new and offbeat targets, and for whom it is often the journey, and not the arrival, that matters.
GALAXY
GC1
RA (2000)
DEC
MAG (V)
Fornax Dwarf NGC 1049 02 39 49 -34 15 29 12.6
M 31 Mayall II (G1) 00 32 47 +39 34 41 13.7
NGC 205 (M 110) G73 00 40 55 +41 41 15 15.0
M 33 C39 01 34 50 +30 21 56 15.9
WLM WLM 1 00 01 50 -15 27 31 16.1
NGC 185 Hodge 5 00 39 14 +48 23 06 16.7
NGC 147 Hodge 3 00 33 15 +48 27 23 17.0
NGC 2403 F46 07 36 29 +65 40 30 17.9

Although not strictly speaking extragalactic, several globular clusters, the brightest of which is M54, belong to the Sagittarius Dwarf Elliptical Galaxy, which is being absorbed into the Milky Way:

One needs to take some care regarding the nomenclature and categorization of objects in the Sagittarius Dwarf galaxy. This galaxy has already been captured by the Milky Way and is inside it and being incorporated into it. Therefore objects in it are no longer "extragalactic" (assuming that term simply means objects outside the Milky Way), even if they were in the distant past. I've had to deal with this problem in writing I'm doing on the four SD globular clusters. One has to be careful to consider/catalogue these objects as in _both_ the SD and the Milky Way. Further complicating things is M 54, which while filling all the requirements of a globular cluster in both galaxies is almost certainly the nucleus of the SD as well. The "dual residency" and nature (for M 54) of these objects is certainly interesting however, and they're all worthwhile observing targets. - Brent Archinal

Other globular clusters belonging to the Sagittarius Dwarf Elliptical are Arp 2 and Terzan 7 and 8.

Imaging Globular Clusters in M31
Three amateur astronomers at the Ferguson Observatory in Northern California have begun an interesting project: imaging regions in M31 and identifying the globular clusters. Click HERE to view their initial efforts.

NGC 1049
Fornax Dwarf (MCG-6-7-1)
Mag (V) = 12.6

The Fornax Dwarf Galaxy is an extremely low surface brightness target but it contains four relatively high surface brightness globulars which you should be able to ferret out even if the galaxy is not visible. The brightest, NGC 1049, was discovered by John Herschel at the Cape of Good Hope and described as "like a star 12th magnitude a very little rubbed out at the edges, a curious little object and easily mistaken for a star, which, however, it certainly is not."
- Steve Gottlieb
Mayall II (G1)
Andromeda Galaxy (M 31)
Mag (V) = 13.7

The brightest globular associated with the Andromeda Galaxy is well away from the galaxy's visible extensions, lying some 2.5 degrees SW of M31's nucleus. It lies at the SW apex of an equilateral triangle of 12th magnitude stars about 2' apart and appears at first glance to be a close triple star! With higher power the central "star" of the three has a soft, fuzzy appearance and is clearly non-stellar.

Steve Gottlieb has observed more than two dozen of the approximately 300 globular clusters in M31. See Globular Clusters in the Andromeda Galaxy.
G73
NGC 205 (M 110)
Mag (V) = 15.0

Globular clusters in three of the Andromeda Galaxy's four brightest companions may be within reach of large amateur scopes. (There are no known globulars associated with M32.) In his 1932 paper identifying globular cluster candidates in M31, Edmund Hubble associated eight objects with NGC 205 on the basis of their physical proximity. In his survey of M31 globulars, Steve Gottlieb has included his observation of the brightest of the eight:

Very faint, visible with direct vision as a 15th magnitude star, on line with a mag 8.5 star 2.5' north and mag 10 star 6.5' north. Located 6' east of the center of M110.
C39
Triangulum Galaxy (M 33)
Mag (V) = 15.9

To find C39, the brightest globular in the Triangulum Galaxy, look for an equilateral triangle of 10th-magnitude stars about 22' SE of the M33's nucleus. The stars are about 7' apart and the southernmost is double. Then find a 12th-magnitude star on the SW leg of the triangle. The globular is about 1' S of this star and is visible with averted vision in a 17.5" scope as a slightly fuzzy star. There are several very faint stars in the same immediate area that make positive identification of the object more difficult.

Rich Jakiel has observed five of the ~60 globulars associated with the Triangulum Galaxy. See Globular Clusters in M33
"WLM 1"
Wolf - Lundmark - Melotte Dwarf (MCG-3-1-15)
Mag (V) = 16.1

The local group galaxy known as "WLM" is named for its discoverers early in the 20th century. Wolf first reported the galaxy in 1909 after photographing the object with a 6-inch camera and the 28-inch Waltz reflector in Heidelburg. Nearly twenty years later, the galaxy was 'rediscovered' by Lundmark and Melotte (1926) during the inspection of older photographic plates. WLM is an easily resolved irregular galaxy that was often a target for Hubble and Baade during the 1920's and 30's. Today, the WLM system is classified as a dwarf irregular galaxy.

20-inch f/4.5 at 175x: A large, fairly weak glow oriented north-south and located in a region of faint stars. The object is elongated ~ 2:1 and has a weakly mottled surface. The globular cluster was only suspected in this FOV. - Rich Jakiel
Hodge 5
NGC 185
Mag (V) = 16.7

NGC 185 and NGC 147 are dwarf elliptical companions of M31 lying about one degree apart and some seven degrees north of M31 itself. Walter Baade first noted the existence of two probable globular clusters in NGC 185 in 1944, and Paul Hodge later identified three more candidates. Hodge 2 (not shown) was later determined to be a background galaxy.

To attempt the brightest of the remaining four (Hodge 5), locate a clump of stars about 3.5' NE of the center of the galaxy. The brightest star in the group is mag 11.7, with two 14th magnitude stars just W. Then use high power and look for a much fainter pair of stars within 1' E of the bright star. This pair forms a roughly equilateral triangle with Hodge 5 at the southern apex. Jens Bohle has reported a successful observation:

I observed FJJ 5 [=Hodge 5] in NGC 185 last fall. It appeared to me stellar and only visible with averted vision less than 50% of the time.
Hodge 3
NGC 147
Mag (V) = 17.0

Walter Baade also identified two globular clusters and a semistellar nucleus in NGC 147. Interestingly, Paul Hodge found that this apparent nucleus (Hodge 1 - mag 17.7; just E of a mag 13.7 field star) is displaced slightly from the center of light distribution. Based upon its color (bluer than the galaxy), he suggested that it is more likely to be a globular cluster.

The brightest globular in NGC 147 (Hodge 3) lies about 3.2' S of the center of the galaxy and 1.5' NW of a mag 12.7 field star. As far as I know, there have been no successful observations of the globulars in NGC 147. Let me know if you have seen them.
F46
NGC 2403
Mag (V) = 17.9

Well, if you made it this far, I guess you are ready for the brightest globular in NGC 2403. It's the only other galaxy I found with a globular cluster brighter than 18th magnitude. Good luck!