Messier 90 is a member of the Virgo Cluster, being one of its largest and brightest spiral galaxies, with an absolute magnitude of around −22 (brighter than the Andromeda Galaxy). Due to the galaxy's interaction with the intracluster medium in its cluster, the galaxy has lost much of its interstellar medium. Consequently, the galaxy's spiral arms appear to be smooth and featureless, rather than knotted like galaxies with extended star formation, which justifies why this galaxy, along with NGC 4921 in the Coma Cluster has been classified as the prototype of an anemic galaxy.
However, its center appears to host significant nebula and star formation, where around 50,000 stars of spectral types O and B that formed around 5 to 6 million years ago are set amidst many A-type supergiants that were born in earlier starbursts, between 15 and 30 million years ago. (Wikipedia)
https://en.wikipedia.org/wiki/Messier_90HISTORY 1 Stacking method SIGMA CLIP AVERAGE
HISTORY 2 De-mosaic bayer pattern used RGGB
HISTORY 3 Colour conversion: Bilinear interpolation interpolation.
EXPTIME = 5400 / Total luminance exposure time in seconds.
SET-TEMP = 0 / Set temperature used for luminance.
LUM_EXP = 600 / Average luminance exposure time.
LUM_CNT = 9 / Luminance images combined.
LUM_DARK = 40 / Darks used for luminance.
LUM_FLAT = 40 / Flats used for luminance.
LUM_BIAS = 80 / Flat-darks used for luminance.
I have been lucky to get a few images this week between storm systems. I shot M90 between darkness and its setting over the observatory wall. The flexibility of shooting short integrations for most galaxies with CMOS cameras is really nice. This image was rescaled 1.5X in PixInsight after processing. Thats why the resolution is listed as 0.4067 '/pixel instead of the correct fits image scale of 0.70 '/pixel with the scope/camera combination.
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