NGC 4631 ,the Whale Galaxy, is an edge-on spiral galaxy in the constellation Canes Venatici. Its slightly distorted wedge shape gives the appearance of a herring or a whale, hence its nickname. Because this nearby galaxy is seen edge-on from Earth, it is observed to better understand the gas and stars located outside the plane of the galaxy.

NGC 4631 contains a central region of intense star formation. This is evident in the emission from ionized hydrogen and interstellar dust heated by these stars. The most massive stars in these regions only burn hydrogen gas through fusion for a short period of time, after which they explode as supernovae. So many supernovae have exploded in the NGC 4631 center that gas is blown out of the galaxy plane. This super-wind has produced a giant, diffuse corona of hot, X-ray emitting gas around the whole galaxy.

NGC 4631 has a nearby companion dwarf elliptical galaxy, NGC 4627. Together they were listed in the Atlas of Peculiar Galaxies as an example of a "double galaxy" or a galaxy pair.

They are also a part of a group including the interacting galaxies NGC 4656 and NGC 4657. However, exact group identification is problematic because of their part of the sky, which is relatively crowded. Estimates of the number of galaxies in this group range from 5 to 27. [Source Wikipedia]

The image was captured with the Meade 12"LX200, using the Atik 383L+ mono at F6.11. I used Astronomik's 12nm Halpha, OIII and SII narrow band filters. All subs were taken at 1x1 bin, -10C, and 10 minutes each.

Ha : 59 subs (9.83 hr) on Apr 6th, 7th, 16th and 19th.

O3 : 30 subs (5.00 hr) on Apr 10th and 11th.

S2 : 30 subs (5.00 hr) on Apr 12th and 14th.

Processing was done with PixInsight, following (for the most part) kayronjm's tutorial of Feb. 24th. Both Ha and O3 were combined to develop the Luminance image. Color mix is my own concoction. See below formulae.

COLOR MIX:

R = .5O3 + .5Ha

G = .15O3 + .85S2

B = S2

North is up. This is a nominal crop. Images continue to be plagued by vignetting, although not as much as my M1. I am not real pleased with this image, especially considering the amount of integration time. Not sure whether the problem is (as suspected) the camera, or if NGC4631 does not take pretty NB images.