Good to see your handle again on IIS, Robert. I’ve been out of the picture awhile and am delighted to be back.
For IIS readers of this thread, Robert’s paper on the Coal Sack is the best of the many I have read. Robert is blessed with clarity, a notion about which most of the professional papers are a bit vague on the concept. I wish varsities would teach writing before they teach calculus. The André and Saraceno paper that Robert cited is a good one, but it nearly extinguished my interest in extinction. IIS readers would be better off reading Robert’s paper to learn about the Coal Sack, then download & print the André and Saraceno maps of the regions you like most to observe. The paper’s web page with links to the maps is hard to navigate. The maps of the fields are presented in four different ways, only one of which we can actually go outside and look at. So I sorted through the unusable stuff and have provided links below to the maps useful to we dweeby folk who actually go outside and look up.
Most dark nebulae are so big they are easier to find naked-eye. After that, wide-field binocs provide those W-O-W views we all yearn for. So here’s the best of the lot. Prepare yourself for a shock: you will be humbled by what you are NOT seeing out there.
Coal Sack Invert the image to negative format, add stars, and that’s what you can see in binoculars. The bad news is: light pollution will ruin your tries. Take a spin out into the countryside, for once you don’t need a car full of gear. A six-pack will do just fine.
Dark Doodad in Musca, and Chamaeleon I & II I can see the Dark Doodad naked eye on the best nights. Come back in 10 million years and that lanky thread will be four glittery balls with bits of nebulosity. Over the next million years the first SN will come along and that will initiate a process that will eventually dissolve the cluster within another ten million years. Easy come, easy go.
Rho Ophiuchi extinction map 6.5° field Someday, all this will be another M4 and NGC 6144. Well, maybe.
Pipe Nebula region 8° field This and the Sagg dark filaments are why Bulge globulars are so awful to spot.
Lupus extinction map 15° field I never thought anything in astronomy could be boring until I arrived at Lupus.
Corona Australis map 4° x 8° field This is the region that makes me feel like I’m a pollywog in a mud puddle. The centre core of the three-cored clump on the right extinguishes 35 magnitudes of whatever’s in it and on the other side. The globular NGC 6723 is just rightward of the clump; it barely escapes being turned into a deeply reddened glowworm like GC 6526.
Serpens-Aquila Rift extinction 12° field The dense core at RA 18.80 Dec –2.00 is why there are no globulars just north of the Scutum Star Cloud, in an area that should be dotted with them like the Ophiuchus group along the RA 18.00 latitude axis.
Orion A & B extinction map 16° x 12° M42 the Orion Neb region is in molecular cloud A and the Horsehead & M78 are in B. If the ambitious owner of a Tak 106FSQ ever gets around to overlaying a montage of this coordinate frame and its extinction map, the result will be The Last Word on the subject of Orion.
Taurus extinction map 18° field Last January I traced the T Tauri complex naked-eye from my 31° South dark site. Even northerly molecular cloud zones can be seen if there’s no light pollution around.
If we lived in the middle of any one of those darker blobs, there would be utterly black and life would be brisk 2° K above absolute zero. The bottom of the Arctic Ocean is positively tropical by compare.
Another item of interest: Astronomers use the term “extinction” as a unit of measure. When they describe molecular cloud collapse, they cite the number of hydrogen atoms in a cubic centimeter from 1 to 10,000. At 10^4 H cc the gas density is high enough to extinguish a star or galaxy on the far side by one magnitude. At that point the astronomers start using Extinction as a calibration measure. I’ve seen Extinctions of 1,000 or more cited in papers devoted to the final collapse into a star—1,000 magnitudes of extinction is a galaxy’s version of a brick wall. Soon after, the collapse becomes a ball of hot rock.
Thanks again to Robert for nudging all this underway.