M12
Globular Cluster in Ophiuchus
About
A globular cluster in Ophiuchus, about 16,400 light-years away, rather loosely packed for its class; it was once classed as an open cluster. A 2006 paper found few low-mass stars in it, which the authors blame on the cluster's crossing of the matter-rich Milky Way plane.
Imaging tips
- At 1,730–2,890 mm on APS-C (2,650–4,420 mm on full frame) the cluster spans a third to half of the frame, about 14′ across.
- Broadband target, no filter needed. One imager kept subs to 30 seconds for 1 hour at f/2, warning that the dense stars show any tracking error or wind.
- That same 1-hour image hinted at faint integrated flux nebulosity across the field, and the imager wished for more time; many hours may bring it out.
- A 12-inch Newtonian at 1,120 mm gathered about 4.9 hours as 2-minute luminance and RGB subs, a reference for a longer, mono-camera plan.
- Best in May and June; it peaks near 38° altitude from 50°N.
Facts
- Size
- 14′
- Magnitude
- 6.7
- Coordinates
- RA 16h 47.2m, Dec −1° 57′
- Framing, APS-C
- 1730–2890 mm
- Framing, full frame
- 2650–4420 mm
- Best months
- May, Jun
- Peak altitude
- 38° from 50°N, 53° from 35°N