B64
Dark Nebula in Ophiuchus
About
A small dark nebula in Ophiuchus, listed in Edward Emerson Barnard's catalogue of dark nebulae. It measures about 5 by 3 arcminutes and shows up only as a patch where background Milky Way stars are blocked.
Imaging tips
- Only about 5 by 3′ across, so it is too small to frame: use a long focal length and a fine pixel scale.
- One imager in Namibia used a 16-inch f/3.75 astrograph with LRGB filters: luminance 4 × 400 s, RGB 4 × 300 s each, plus Hα 2 × 900 s.
- A 1.98° field from that setup also held the globular cluster M9 and NGC 6333, so a wider lens frames the nebula among bright neighbours.
- Another imager used a 200 mm lens with 54 × 2 minutes (1 h 48 min); the field also took in B63 and about two dozen other Barnard nebulae.
- Best around May and June; it stays below 22° altitude from 50°N.
Facts
- Size
- 5′ × 3′
- Magnitude
- —
- Coordinates
- RA 17h 17.4m, Dec −18° 31′
- Framing, APS-C
- longer than 4000 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- May, Jun
- Peak altitude
- 22° from 50°N, 37° from 35°N