Object of the Week, April 6, 2014 - Djorgovski 2 = ESO 456-SC38

Object of the Week, April 6, 2014
Djorgovski 2 = ESO 456-SC38
Sagittarius
Mag 11?
R.A.: 18h01m49.0s Dec.: -27°49'30" (2000)

I first learned of this once obscure globular cluster in July 1999 when Barbara Wilson posted an observation to IAAC, and Barbara apparently learned of it from Andrew Murrell of Australia via private communication. As I have just today returned from an observing trip to Australia, where I observed side-by-side with Andrew (again!) and other advanced observers over several nights, I thought it would be appropriate to revisit this surprisingly bright object once again.

Djorg 2 is an easy guy to find, being located virtually next door to both the very pretty NGC 6520 and perhaps the best dark nebula in the sky, B 86, aka The Inkspot. All 3 objects will fit into a field of view only 24 arc-minutes wide, so just about any low-power eyepiece will show them all. If you draw a line from the far side of NGC 6520 through the center of that cluster and also through the center of B 86, and then extend that line about twice that distance you will be right on top of Djorg 2, which resides dead center in a Hercules-type keystone of stars, see the photo.

Attachment 1157

Djorg 2 is easy to see, and reportedly has been spotted in small refractors. It is amazing that it was not discovered until 1987! It is 3 to 4 arc-seconds across, and has been dimmed by about 8 magnitudes by interstellar dust. Think about this; adding 8 magnitudes by eliminating the dust would put it at mag 3... and Omega Centauri is mag 3.9... just sayin'... anyhow, Djorg 2 appears as a bright fuzzy spot, and at first glance no stars are resolved... but after a close look, perhaps a few stars around the edges are visible... at least, using a 30" telescope there are several stellarings that pop into view :D

As always, give it a go and let us know!

A nice object. Here are my notes from September 2004 using a 25" f/5 at 30 deg. north:

"A pretty g.c., barely noticeable at 77x, obvious at 185x, with a triangular appearance. Higher power reveals the triangle to be composed of three brighter stars in an almost equilateral triangle, but with a disc of fainter stars behind. At 450x a couple of dozen stars resolved with averted vision.

At 77x, shares the fov with B86 & NGC 6520."

Jim

I've seen this lovely object many times as a by product of observing NGC 6520 and B86, but have taken notes for Djorgovski 2 as a separate object only once with my 20 inch f5 from the 2002 Oregon Star Party:

"Very faint globular near NGC 6520/B86. A faint patch at low power that looks very much like a galaxy, but once power is upped to 261x some of the brighter stars are resolved. Very cool - its distance and obscuration by the Milky Way seems obvious. NELM 6.4+"

This was well before I had a SQM and the NELM notation of "6.4+" means that it was a very dark and transparent night. This is one of my favorite areas to sweep up dark nebulae and revel in the incredible star density.

From Hakos / Namibia (23°S) I noted:

24", 141x-300x, NELM 7m+
with 141x small but prominent glow W of B86 which shows hints of resolution; with 300x trapezoidal form, completely resolved, little concentration to its middle

" but once power is upped to 261x some of the brighter stars are resolved.

I too have seen it with a 20" at 300+x and it was resolved into a half dozen stars.