M81 is a spiral galaxy with a relatively modest diameter of 60,000 light years. In 1993, the observation of about thirty cepheids by the Hubble telescope made it possible to estimate the distance of the galaxy at 11.8 million light years, making it one of the closest to ours. It is part of the same group of galaxies as M82, the G2 group (list of Vaucouleurs). This group is part of the supercluster of the Virgin, as is our local group.
M81 cannot be seen without an instrument. It is clearly visible with binoculars because of its magnitude of 6.9. In a 114 mm telescope, the nucleus appears as bright and surrounded by a diffuse halo. A 350 mm instrument and good observation conditions are needed to detect the spiral arms of the galaxy.
Shooting Instruments.
TS-Optics 300mm/12″ ONTC f/4 Newtonian (carbon tube)
Imaging Cameras.
QHYCCD QHY294 Pro
Mounts
iOptron CEM120
Unit images:
Chroma Blue 36 mm: 23×180′′(1h 9′) -25°C bin 1×1
Chroma Green 36 mm: 22×180′′(1h 6′) -25°C bin 1×1
Chroma H-alpha 3nm Bandpass 36 mm: 99×300′′(8h 15′) -25°C bin 1×1
Chroma Lum 36 mm: 87×180′′(4h 21′) -25°C bin 1×1
Chroma Red 36 mm: 25×180′′(1h 15′) -25°C bin 1×1
Integration: 16h 6′