C42
Globular Cluster in Delphinus
About
A globular cluster in Delphinus, about 135,000 light-years away in the Milky Way's outer halo. Its eccentric orbit hints that it formed in a small galaxy and was captured later. Hubble images of it show faint background galaxies.
Imaging tips
- Only about 4′ across in the catalogue, so it is too small to frame: use a long focal length and a fine pixel scale.
- Faint for a cluster at 22.2 mag/arcsec², and a star cluster needs broadband. One unguided image used just 104 × 20 s, about 35 minutes.
- Zoom into the stack: faint background galaxies show up in the field in a ground-based image as well as in Hubble's.
- Best around July and August; it peaks near 56° altitude from 50°N.
Facts
- Size
- 4.2′
- Magnitude
- 10.5
- Coordinates
- RA 21h 1.5m, Dec +16° 11′
- Framing, APS-C
- longer than 4000 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- Jul, Aug
- Peak altitude
- 56° from 50°N, 71° from 35°N