For many years, the Sombrero has been one of my Great White Whales.  Back in 2014, I first shot a few frames of the Sombrero from Oregon with my DSLR on a C14 XLT.  I posted one of those frames and frankly, it was terrible.  That image was more of a mile marker than a real imaging effort.  The problem was that in Oregon, M104 appears in a place in the sky that was really hard for me to get at--no matter what telescope I used.   So, when I moved my scope down to New Mexico, I figured that I'd finally be able to snag some good data; but that was never the case.  For one reason or another, the weather would always screw up my efforts.  If it wasn't clouds, it was the seeing, and if it wasn't the seeing it would be the wind, or dew, or something else.  No matter what I did, I could never get enough good images to produce a reasonable result!  And, there it was--the galaxy that I could never seem to image.

So, back in March when I spotted the Sombrero rising in the Chilean sky, I just had to give it a go.  Of course the one lesson that I continue to learn is that NOTHING is ever easy!  March is Fall in the Southern Hemisphere and that's when the seeing should be pretty decent; but, last Fall was a lead-in to one of the worst winters in the last ten years for the southern Atacama.  The winter weather was great for the desert ecosystem, but with wind, rain, snow, clouds, and generally terrible conditions, it was terrible for imaging!  I started this project thinking that it wouldn't take long to gather enough data so that I could move on to something a bit less "common", but that turned out to be wrong.  Right away I could see that things weren't going well.  Between the seeing and the wind, my guiding numbers looked really mediocre.  So, I set up to gather nearly 150 subs in each channel figuring that I'd grab at least some good data.  It turned out to be a challenge to recover more than roughly 25, 10 minute useable subs in each channel so I had to relax my quality threshold a bit to turn it into an image.

M104 is a peculiar galaxy of unclear classification that was discovered in 1781 by the French astronomer and comet hunter Pierre Méchain, one of Charles Messier’s colleagues.  It lies at a distance of about 31 mly and has an apparent brightness of 8.0, which is quite bright.  It is about a third the diameter of the Milky Way with a very bright nucleus and an unusual large central bulge that resembles a sombrero.  Its most interesting feature is the prominent, detailed dust lane along the edge of the disk.  At the core of the galaxy lies a super massive black hole with a mass estimated to be around one billion (1e^9) solar masses, which is among the most massive yet detected.  The nucleus is a strong source of synchrotron radiation emitting in the X-ray band.  Synchrotron radiation is normally emitted by accelerating charged particles such as electrons; however, in the case of a black hole, synchrotron emission occurs as the result of ultra-relativistic motion of electrons following a  path close to the event horizon at the edge of the photosphere.  The nucleus of the galaxy is classified as a "low-ionization nuclear emission-line region" when means that ions in this region are weakly ionized.  Studies indicate that the nucleus has virtually no star formation activity.  One other interesting aspect of the Sombrero is that it has a relatively large number of globular cluster--in the range of 1,200 to 2,000.  The high number of globular clusters is thought to be related to the size of the central bulge.

With only 21 subs in the Lum-channel below 1.9" FWHM, I created a synthetic Lum signal from the linearized RGB data.  I used the PI ImageIntegration tool to combine that data with the Lum data using SNR weighting.  The trick is to duplicate each of the two frames to get around the 3 frame minimum frame limitation imposed by the ImageIntegration tool.  I was moderately aggressive with the deconvolution tool to attempt to sharpen just the central dust lane, doing two full runs to sharpen the data in the Lum channel.  I used the white regions around the central dust lane to define "white" for the color balance, although it came out very slightly too blue for my taste so I "manually" warmed the color balance very slightly afterwards.  After looking at the balance of the surrounding star field, I'm pretty satisfied with this color selection.  The other significant challenge with M104 lies in how to handle the massive central glow.  For this image, I applied a little bit of highlight compression in PS along with a decrease in the white level to bring out the core.  This correction doesn't significantly detract from the glow but it does make the core a bit more distinct.  My feeling is that I had hoped that with a 20" scope, I could bring out a bit more detail in the dust lanes and the disk, but overall, this is a pretty tough object and I fell a little short of my hopes.  Regardless, this isn't a bad "first effort" given the challenges that I experienced with the seeing.  My initial hopes for sub-arc second seeing in Chile were clearly wishful thinking!  (If anyone want to see it, I've got gobs of data with 3" - 4" FWHM!)

As usual, I'm happy to answer questions and I'm receptive to C&C so feel free to let me know what you think.

- John