Not a Comet Number 94

Image of M94
The Galaxy Messier 94

This galaxy is #94 in Charles Messier’s catalog of objects that — at least initially, was meant to identify things that were not to be mistaken for a comet. Eventually the list really is just a catalog of interesting objects, but this galaxy in the (somewhat) northern constellation of Canes Venatici surely must have been a target that could easily be mistaken for the head of a comet. The core of this galaxy is quite bright, and there is a faint, but not hard to capture photographically, halo of stars surrounding the core.

I took this image with a 6″ Esprit refractor hosted in the dark skies of the California desert near Lake San Antonio. This is my second major project with a CMOS camera using the Sony IMX 455 sensor. The very core of the galaxy is still a little over exposed with only three minute exposures through Red, Green, and Blue filters, and I did a few 5 minute exposures in Luminance. The halo of stars came out readily, which is a testament to the low read noise of the sensor. However, there is actually another stream of stars that extends from this ring that shows up in some deeper exposures that I did not pick up. Keeping the core from saturating, and still picking up the star streams is a challenge. I’m going to have to attempt this target again sometime to see if I can get the full dynamic range with one length of exposure time.

Another processing challenge to this image has to do with the halo. It is very faint, and the gradient tappers gradually into the background. There’s even what appears to be some Hydrogen Beta star forming details in the top section of the ring from this image. However, getting this ring to look right is a challenge. I processed the image in PixInsight and Photoshop on two computers that are color calibrated, and the image is set to use the sRGB color space. However, in some browsers, and in an email client, the halo is very blocky and mottled. On my iOS devices, the ring is rendered quite beautifully with no artifacts. So… when you look at this, depending on your device, the halo may be blocky and garish slightly, or smooth and subtle. We still have a ways to go it seems with computer display technology, and this image seems to push those boundaries as well.