B68 — Black Cloud
Dark Nebula in Ophiuchus
About
A dark cloud in Ophiuchus, also called a Bok globule, about 407 light-years away and with a diameter near 0.5 light-years. It is opaque at visible wavelengths, and its sharp edges suggest it is close to collapse, possibly forming a star within about 200,000 years.
Imaging tips
- At 2020–3370 mm on APS-C the cloud, about 12 by 8′, fills a third to half of the frame; on full frame use 3090–5160 mm.
- Broadband suits a dark cloud: it shows only as a gap in the star field, so contrast depends on the rich Milky Way background behind it.
- One imager's 784 mm frame, 97 by 65′ with 7 × 8 minutes through a CLS filter, placed it lower right of the Snake.
- Best in May and June; it peaks near 16° altitude from 50°N, and a dark sky protects the contrast.
Facts
- Size
- 12′ × 8′
- Magnitude
- —
- Coordinates
- RA 17h 22.6m, Dec −23° 50′
- Framing, APS-C
- 2020–3370 mm
- Framing, full frame
- 3090–5160 mm
- Best months
- May, Jun
- Peak altitude
- 16° from 50°N, 31° from 35°N