by Steve Gottlieb
But let's back up a week or two. The setting was 8 nights at the Magellan Observatory (http://home.goulburn.net.au/~magellan/) in rural New South Wales, about three and half hours southeast of Sydney in the Southern Tablelands. Instead of tropical T-shirt weather, it was a few degrees below freezing in the cold winter nights. But I was quite comfortable within the confines of the 4.5 meter dome housing a fork-mounted 18-inch NGT from JMI. Six of the eight nights were spent in the dome, though I probably had the equivalent of 4 full nights to explore the southern skies. As this was my second trip to Oz and third southern skies trip, I've had the fortune of observing all the well-known far southern showpieces, so I spent some time on some of the lesser explored treasures. High on my observing list was the "Dark Doodad", a huge dark streamer in the tiny constellation of Musca, named nearly 20 years back by Dennis di Cicco on an image he took from Alice Springs in the center of Australia.
This distinctive dust lane is located north of the globular cluster NGC 4372, a little-known showpiece in its own right (see http://www.astrosurf.com/antilhue/ngc4372.htm) way down at -72 degrees declination. At 171x, this large, bright globular was an impressive object and beautifully resolved into 150-200 stars mag 13 and fainter within a 13'-14' diameter. The unresolved background glow was relatively faint for such as a well-resolved globular. The large 4' core is only slightly brighter and there is no nucleus (class 12 concentration) although a close pair of brighter mag 12.5 stars is near the center. Scores of stars appear linked in chains and loops, particularly in the outer halo, which is quite irregular and ragged. Mag 6.6 HD 107947 lies 5.5' NW of center at the edge of the halo and provides a striking contrast although it detracts somewhat from viewing. A dust lane appears to pierce the cluster on the north side for a few arc minutes (east of the bright star) and this dark intrusion may be an extension of the "Dark Doodad".
The main stream of the Doodad appears to originate on the NW side of the cluster beyond the mag 6.6 star that resides in the outer halo, perhaps 25' from the center. At 76x (51' field), this dark streamer can be easily traced curving to the NE for nearly three eyepiece fields as a fairly high contrast wide dust lane of surprisingly equal width that cuts a broad starless path through the Milky Way! The surrounding Milky Way field is quite rich here so the edges of the dark lane are clearly defined and the total size is roughly 150'x15'! Along the way it passes well to the north of mag 3.8 Gamma Muscae which is situated 44' NE of the cluster. This is a pretty startling object once the entire length is traced and was easier to view than I expected. Unfortunately, I didn't look for it in my binoculars, but I would expect this lane to stand out well. A nice wide-field image of this region can be found at http://www.astronomie.be/hambsch/namibia2/n4372.htm, though the image is rotate 90 degree counterclockwise. As far as I know, the "Doodad" has never been formally catalogued, testifying the intrepid southern observer can still uncover new treasures. More adventures to follow...
Posted on sf-bay-tac Jul 29, 2005 19:27:38 PT
Converted by report.pm 1.2 Mar 06, 2006 21:21:26 PT