Cr39
Open Cluster in Perseus
About
A young open cluster in Perseus about 570 light-years away, known as the Alpha Persei Cluster and as Melotte 20. Its brightest member is Mirfak, a yellow supergiant near magnitude 1.8, and most of the other bright members are hot blue stars. Age estimates run from about 50 to 70 million years.
Imaging tips
- Sources give its span as roughly 3° to 6°, so use a wide lens or plan a mosaic.
- One imager used a 180 mm lens for a 5.91° × 3.95° field: 3 × 300 s plus 3 × 600 s, 45 minutes in all, through a light-pollution filter.
- The stars are the subject, so broadband is the right choice.
- In that same 180 mm frame the open cluster NGC 1245, about 10′ across, sat in the bottom right corner.
- Best in October and November, when it peaks near 89° altitude from 50°N.
Facts
- Size
- 366′
- Magnitude
- 1.2
- Coordinates
- RA 3h 26.5m, Dec +48° 59′
- Framing, APS-C
- 70–110 mm
- Framing, full frame
- 100–170 mm
- Best months
- Oct, Nov
- Peak altitude
- 89° from 50°N, 76° from 35°N