Arp81
Galaxy in Draco
About
Two interacting galaxies in Draco, about 300 million light-years away: NGC 6621 and NGC 6622. Their closest pass was roughly 100 million years back and stretched NGC 6621 into a tail that curls behind it. Hubble images show more young, massive clusters than in the Antennae galaxies.
Imaging tips
- Only about 3′ × 2′ in total, so it is too small to frame: use a long focal length and a fine pixel scale.
- At 23.8 mag/arcsec² the surface brightness is low, so plan many hours of broadband data to bring out the tidal tail.
- One imager used a Newtonian with a 1.452 arcsec/pixel scale and a 41.2′ field, which held both NGC 6621 and NGC 6622.
- That imager collected 1 h 56 min of luminance and 20 minutes each of red, green and blue, 2 h 56 min in total.
- Best around June and July; it peaks near 72° altitude from 50°N.
Facts
- Size
- 3′ × 2′
- Magnitude
- 13.2
- Coordinates
- RA 18h 13.0m, Dec +68° 22′
- Framing, APS-C
- longer than 4000 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- Jun, Jul
- Peak altitude
- 72° from 50°N, 57° from 35°N