Description (Adapted from Steve Mandel, Robert Gendler, APOD, and SEDS):
M81 was discovered by Johann Elert Bode in 1774. M81 is one of the easiest galaxies to observe for amateur astronomers. With its total visual magnitude of about 6.8, it can be found with most amateur small telescopes. Bode described M81 as a "nebulous patch", about 3/4 of a degrees away from M82, and it "appears mostly round and has a dense nucleus in the middle". Pierre Méchain independently rediscovered both galaxies as nebulous patches in August 1779 and reported them to Charles Messier, who added them to his catalog after his position measurement on February 9, 1781. M81 is the brightest member of the nearby galactic group, the "M81 group". The true distance of M81 is 12 million light years. Investigations performed in 1994 have indicated that M81 has probably only little dark matter, hence is estimated to have less than that of average galaxies.
The Dwarf irregular galaxy, Holmberg IX, (seen above M81 in the image) most likely condensed from tidal debris left over from this event. (Note the hydrogen-rich star-forming nebular regions clearly visible in this dwarf galaxy.)
Equipment: (SMAP/FTO and Astroden)
- TMB203 F/7
- SBIG STL-6303E
- Paramount ME
Exposures:
- Luminance: 48x15 minute subs, 12 hours
- Red: 25x15 minute subs, 6.25 hours
- Green: 27x15 minute subs, 6.75 hours
- Blue: 28x15 minute subs, 7 hours
- Ha: 8x30 minute subs, 4 hours
Totaling 36 hours
Processing:
- Calibration, registration, normalization, data rejection, RGB combine, sLum, denoising, and deconvolution in CCDStack.
- Photoshop CS2: Noise control, match color boost for saturation, Rob Gendler's LLRGB technique, a bit of extra deconvolution, contrasting
- Other color adjustments and enhancements