NGC 3631 (Arp 27) spiral galaxy type Sc, in Ursa Major. Arp 27 is in the class of spiral galaxies with
one heavy arm and the atlas note is “Note straight arms, absorption tube crossing from inside to outside
of S arm”. Taken in average to poor transparency March 30, April 16, 18, 19 2009 with CCD Lab’s
Q285M and a C8N at f5 on a Losmandy G11/Gemini mount. L subframes were 5 minutes binned 1x1
while the RGB subframes were 3 minutes binned 2x2 resulting in the following total exposures L:R:G:B
(min) = 280:48:48:48. Captured with Nebulosity, calibrated and sigma combined in Iris with other
processing using PixInsight LE and Photoshop CS. North is up.