Saturday, May 19, 2018

The Dark Deep Sky

An observing report from this morning.  Images are from my archives.


May 19, 2018
1:15 AM – 2:45 AM

Skies clear with above average transparency. Limiting magnitude 7.0 + SQM 21.7 MPSAS

Milky Way vivid even on the south horizon. The dark nebulae in southern Ophiuchus obvious to the unaided eye. Spectacular conditions compared to previous observing sessions this spring.

I had setup the tripod the previous evening, gotup at 1:00 AM and set the binocular. I used the BT-100 with 18mm UF (31X @ 2.1º) and began observing the area of Antares. Enjoyed the beautiful triplet star Rho-Oph. Looking southward, Antares, Messier 4 and NGC-6144 fit neatly inside the eyepiece field. Messier 4 was resolved with the prominent bar noted. Panning east from this region the dark streamer Barnard 44 continued for several fields, then I continued to the wonderful chain of stars stemming northward from Theta Ophiuchi. This asterism appears to be unnamed. It begins with Theta and gently arcs northward with proceedingly fainter stars.

The Dark Streamers East of The Antares Region

Slightly north and east of Theta Oph is 44 Ophiuchi. This is the springboard of the somewhat faint but rich area of Milky Way strata littered with dark nebulae. It includes the famous Barnard 72, the Snake Nebula. I have attempted this dark nebula before, but under less than favorable conditions. During the early morning I returned to this area as it came to culmination. I'm happy to report that it was well seen. Even the small round B68 was visible just to its south. Barnard 261 to the northeast was also visible in field. Barnard 72 revealed its coil only with averted vision at first until I learned the area. Somewhat higher power may be a better combination to behold it. This was a bucket list object and I'm tickled to have seen it, especially in such a wide-field view!

The Region Of Southern Ophiuchus

Panning this area, countless dark nebulae are seen and it would have been overwhelming to try to account for them all. Panning southward and entering the Pipe Nebula, LDN1773, I hovered over the sixth magnitude star HIP 85783, located within the bowl of the Pipe. Even with a two degree field the field held only a few members and was practically starless. A lonely field in such a rich part of the sky.

Panning eastward and into the Great Rift one cannot be prepared for what is perhaps the greatest Milky Way sweep in the entire sky. Approaching the dark estuaries of the Great Sagittarius Star Cloud is a existential experience. Under dark and transparent skies, approaching this area is surreal. This is one of the grandest views in all the sky, yet few seem to have experienced it.

The Great Star Cloud of Sagittarius 

The dark voids and shoals of the Great Star Cloud appear abruptly from the west. Panning along the cloud's jagged perimeter, which runs along the Galactic Equator from Messier 8 and southward to the area encompassing Messier 6 and 7, amounts to the brightest deep sky tour in all the Milky Way. To truly appreciate however, dark transparent skies are a must.

While the west side of the Great Cloud offers the most dramatic view, the central interior of the cloud is also rich in a dark tapestry. In an area extending south from 11 Sagittarii (just east of Messier 8) to Gamma Sagittarii, the area is strewn with dark features layered over the brilliant star cloud. Barnard 90 stand out as one prominent example of these dark objects seen against the brighter stellar stratum.

To the north of this region is Sagittarius' lesser cloud. The Small Sagitarius Star Cloud, Messier 24, is a wonderful object adorned with a surplus of dark nebulae, star chains and neighboring clusters. Along with the Scutum Star Cloud and the Great Cloud of Sagittarius, Messier 24 and its denizens rank as the finest in the sky. In the 2º field, M24 is a delight. Brilliant stars compose the major cloud and small dark nebulae, such as B92 and B93, on its northern edge provide stark contrast to the view. Other dark nebulae such as Barnard 304 appeared along the northern section, stemming from near B92 and meandering southwestward. Also, other dark features, such as “The Forks” on the east side of the cloud. Within the cloud, the tight open cluster NGC-6603 stood out plainly and showed partial resolution.

The Small Sagittarius Star Cloud Region

The southern side of messier 24 is dark and the southwest end of the cloud transitions into what I call, “The Blade”. The dark region makes a right angled appearance to the “edge” of this knife-like feature.
The emission nebulae IC1284 resides in this same dark region south of M24. The two stars just west of IC1284 exhibit reflection nebulae, these are VDB 118 and VDB 119. VDB 119 was seen with an obvious condensation.

West of M24, Messier 23 is a grand open cluster with bright members. To it's north Barnard 84a is a vertical black tadpole with a solitary ~10th magnitude star superimposed. North of M24, Messier 17 is a grand view. The swan appearance is plain, but also the outer loop seen in long exposures is evident with direct vision.

North and east of M24 is a curious object, Barnard 312. This object is perhaps most impressive because contrast and delineation is very high. Visually this object surpasses the photographs I have made, or have seen. The soft glow of the stratum north of this object appears to glow, in part due to the immediate darkness of the nimbus. An interesting object and was always interested in it after finding in my photographs of the Milky Way about ten years ago.

Messier 8 Region

The Lagoon Nebula, Messier 8 as seen in the BT-100 is well seen. The bright hourglass feature, along with the bright open cluster NGC-6530 and the fainter periphery of nebulae are all encompassed in the 2º field. The view is incredible. The binocular reveals stunning contrast of this scene and it scarcely seems real. Also visible in the field is the globular 6544 and to its south, NGC-6553. Lots of subtle detail wherever you look, some on atlases, some are not. Seeing deeply into this area of the galaxy is a joy.

Binocular Astronomy Under The Dark Skies of Downeast Maine