NGC 6539 (GCL 85) Globular Cluster in Serpens

Located at: RA 18 hours 04 minutes 50 seconds, Dec -07 degrees 35 minutes 09 seconds

Size: 7.9' Magnitude: 8.9 Class: 10

North is up

West to the right

Telescope:

14.5" f5 Newtonian reflector

Camera:

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

Image:

 Lumicon Red filter, 390 minutes (39 x 10 minute subs), 08/8/9/2015; seeing 2.2-3.4 FWHM per CCDStack

Processing:

CCDStack 2.90.5589.16047, Photoshop CS5.1

Location:

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

Notes: See the 8" version.

From the NGC / IC Project:

Contemporary Visual Observation(s) for NGC 6539

NGC 6539
18 04 49.7 -07 35 09
V = 9.8;  Size 6.9

18" (7/19/04): at 225x appears fairly faint, moderately large, round, weakly 
concentration.  The diameter is ~3.5' diameter with averted vision.  A few mag 
15-15.5 stars are along the west edge of the halo with some brighter mag 13 
stars off to the W and NW.  At 435x, 3 or 4 mag 15 stars are grouped near the 
west edge of the halo and a single mag 15.5-16 star is near the center.  The 
edges appear ragged at this magnification.

18" (8/23/03): at 323x appears fairly faint, round, pretty diffuse with only a 
broad, fairly weak concentration.  A mag 12.5 star is off the NW side and a few 
mag 13 stars are off the SW edge and further off the SE side.  A couple of mag 
15 stars are resolved between the two brighter stars on the west side. At 435x, 
the surface brightness is quite mottled and seems on the verge of resolution but 
only one or two extremely faint stellar sparkles are intermittently visible.

17.5" (8/10/91): fairly faint, moderately large, 3' diameter, round, diffuse, 
broad weak concentration.  A number of stars are very near including a mag 12.5 
star off the NW edge and a fainter mag 13.5 star off the SE edge.  In addition, 
an extremely faint 15th mag star is resolved near the NW edge and a mag 15 star 
is visible near the center but no other resolution was evident.

8": faint, moderately large, very diffuse, no resolution.

- by Steve Gottlieb