…continuedSeeking Summer's Dark Nebulae
Holes in the Heavens
William Herschel's Hole in the Heavens near Rho Ophiuchi is a nearly starless area stretching for field after field at 120x in the 24-inch Cassegrain of the Prince George Observatory in central British Columbia. According to Burnham's Celestial Handbook, Herschel had the whimsical idea that the nearby globular cluster M80 might have formed from the "missing" stars.
Black and roughly triangular, little Barnard 86 (4.5' by 3') stands out dramatically in the Sagittarius starcloud through any telescope from a 4-inch RFT on up. The adjacent open cluster NGC 6520 heightens the contrast between darkness and light. Located 2.7° north-northwest of Gamma Sagittarii, B86 culminates only 13° above the Mount Kobau horizon, so I hadn't looked for this inkblot until John Dobson showed me 12 years ago that it could be seen from so far north. This first view of the dark mass between an open cluster on one side and a red star on the other with Dobson's magnificent 18-inch mirror is still the best that I have ever enjoyed.
RFTs or binoculars reveal sinuous dusky ribbons in many Milky Way fields. Spend some time slowly sweeping the Sagittarius starcloud and the Scorpius Milky Way. You will find them marbled with faint contrast features on the most memorable nights.