Spiral Galaxy in Ursa Major

Uploaded 3/06/02

Part of a small galaxy group, M81 and nearby M82 (the "exploding galaxy") form a spectacular pair high in the sky on spring evenings. A bright 7.9 magnitude, and a huge 27x14 arcmins in size, this object does not quite fit my 15 min. field in its entirety. An Sb spiral, the central salmon pink core is crossed by rust brown dust lanes that spiral almost into the core. The pale blue arms contain large numbers of HII regions, pink in color - the holy grail of the CCD galaxy photographer. Interestingly enough, the two bright stars just below the core are listed as "Non Stars" in the Hubble Guidestar Catalog. This image is a L+R(RGB) image. This means half the luminosity exposure was with a red filter, and half with a clear filter. This has the effect of boosting the visibility of the HII regions, and also cutting sky fog.

Processing: L=5x6m clear + 3x10m red. DDP, followed by RL deconvolution, then to preserve the core as a sharp point and bring up the arms, luminance masking was used with two images in Photoshop 6. LAB composite in Photoshop.

Instrument:  12.5" f/5 Home made Newtonian
Platform:  Astrophysics 1200 QMD
CCD Camera:  SBIG ST7E w/Enhanced Cooling
Exposure:  L(LRGB) = 60:20:20:36 (RGB Binned 2x2)
Filters:  RGB Tricolor
Location:  Payson, Arizona
Elevation:  5150 ft.
Sky:  Seeing FMHW = 2.3 arcsec, Transparency 8/10
Outside Temperature:  0 C
CCD Temperature:  -35 C
Processing:  Maxim DL, Photoshop, AIP4WIN, PW Pro.




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