M2
Globular Cluster in Aquarius
About
A rich globular cluster of about 150,000 stars in Aquarius, roughly 38,000 light-years away and about 175 light-years across. Gaia data show a long tidal stream of stars about 45° across the sky linked to it.
Imaging tips
- At 1,860–3,110 mm on APS-C (2,860–4,760 mm on full frame) the cluster spans a third to half of the frame; it is about 13′ across.
- It is bright enough for short subs: one imager guided nothing at all, stacking 31 × 10 s and 73 × 4 s frames through a light-pollution filter.
- A one-shot colour camera on a fast f/3.9 astrograph gave a usable result from 20 × 3 min, even through wildfire smoke; the authors regret stopping at one hour.
- At 20.7 mag/arcsec² it needs no narrowband filter. Best in July and August; it stays below 39° altitude from 50°N.
Facts
- Size
- 13′
- Magnitude
- 6.5
- Coordinates
- RA 21h 33.5m, Dec −0° 49′
- Framing, APS-C
- 1860–3110 mm
- Framing, full frame
- 2860–4760 mm
- Best months
- Jul, Aug
- Peak altitude
- 39° from 50°N, 54° from 35°N