H-NGC6939
Open Cluster in Cepheus
About
An old open cluster in Cepheus, about 3,860 light-years away. Age estimates vary from about 1 to 2.2 billion years. Several of its red giants vary in brightness. NGC 6946, a spiral galaxy, sits about two thirds of a degree to the southeast.
Imaging tips
- Framing runs from 3030 to 5050 mm on APS-C for the cluster alone. NGC 6946 is about 40′ away, so fitting both needs a much wider field.
- Both objects have been captured together: one imager gave them 40 h 50 min of 5-minute subs, mostly through an Optolong L-Quad Enhance multi-band filter plus 3 h 40 min through an L-eXtreme.
- The same image shows a good deal of integrated flux nebula in the field.
- Surface brightness is 20.9 mag/arcsec². Best in July and August, reaching about 79° from 50°N.
Facts
- Size
- 8′
- Magnitude
- 7.8
- Coordinates
- RA 20h 31.7m, Dec +60° 39′
- Framing, APS-C
- 3030–5050 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- Jul, Aug
- Peak altitude
- 79° from 50°N, 64° from 35°N