M101 — Pinwheel Galaxy
Galaxy in Ursa Major
About
A large face-on spiral galaxy about 21 million light-years away, roughly three times the width of the Milky Way. It is rich in glowing star-forming regions, and six supernovae have been recorded in it, the brightest being SN 2011fe.
Imaging tips
- Spans about 29′, so 840–1,390 mm on APS-C frames it well. A wider 400 mm lens shows more neighbouring galaxies but less of its structure.
- Surface brightness is faint, about 23.8 mag/arcsec². The outer arms appear only with long total integration: one urban-sky project used 100 hours.
- Hα data from a dual-band filter makes the star-forming regions in the arms stand out against the broadband colour.
- Subs of about 2 minutes worked from a bright suburban sky; discarding the weakest frames helps. Best placed in April and May.
Facts
- Size
- 29′ × 27′
- Magnitude
- 7.9
- Coordinates
- RA 14h 3.2m, Dec +54° 21′
- Framing, APS-C
- 840–1390 mm
- Framing, full frame
- 1280–2130 mm
- Best months
- Apr, May
- Peak altitude
- 86° from 50°N, 71° from 35°N