M10
Globular Cluster in Ophiuchus
About
A globular cluster in Ophiuchus, about 14,300 light-years away, with a concentration of blue straggler stars in its core and two known millisecond pulsars. Messier described it in 1764 as a nebula without stars.
Imaging tips
- At 1,620–2,690 mm on APS-C (2,480–4,130 mm on full frame) the cluster spans a third to half of the frame, about 15′ across.
- A small 70 mm refractor with 30-second LRGB subs for one hour was enough for a usable image, though its authors found the cluster neither impressive nor colourful.
- Another imager used just two 10-minute subs per RGB channel at 530 mm focal length.
- M12 is about 3.25° away; a 180 mm lens with 20 four-minute subs covered both in a 5° × 3.4° field.
- Best in May and June; it stays below 36° altitude from 50°N.
Facts
- Size
- 15′
- Magnitude
- 6.6
- Coordinates
- RA 16h 57.1m, Dec −4° 6′
- Framing, APS-C
- 1620–2690 mm
- Framing, full frame
- 2480–4130 mm
- Best months
- May, Jun
- Peak altitude
- 36° from 50°N, 51° from 35°N