C47
Globular Cluster in Delphinus
About
A globular cluster in Delphinus, about 52,000 light-years away and roughly 90 light-years across. William Herschel found it in 1785. Its stars include dozens of RR Lyrae variables, and its orbit is unusually stretched. Caldwell 47.
Imaging tips
- At roughly 6′ across it is too small to frame: use a long focal length and a fine pixel scale.
- A globular cluster, so broadband filters suit it; a 6-hour luminance-plus-RGB set at 1,120 mm shows it filling only a small part of the frame.
- A plain, round cluster with no standout detail; a 32-minute stack at 1,600 mm already records it, with the stars as the interest.
- Best around July and August; it peaks near 47° from 50°N.
Facts
- Size
- 6.2′
- Magnitude
- 8.8
- Coordinates
- RA 20h 34.2m, Dec +7° 24′
- Framing, APS-C
- 3910–6520 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- Jul, Aug
- Peak altitude
- 47° from 50°N, 62° from 35°N