The Night of the Comet

We finally got a short break from monsoon weather and I had a clear, moonless night. I had intended to use it to get RGB data for the Helix Nebula (see below), but the Helix doesn't clear the mountain to my southeast until about 10:30 PM so I needed to start with a different target. I set up my scope for the Helix (no focal reducer, using a nebula filter--the Baader UHC-S), and thought I might try the Bubble Nebula in RGB for an hour or two first. But then I remembered that Comet Jacques is in a good part of the sky for me and decided to try to find it. I googled its position and found it was in Cepheus midway between two of the brighter stars in the asterism. Finding the comet was pretty easy because I could see a fuzzy patch with 1 sec exposures in my guide scope. About then the fun began.

Well, actually the fun began several days before, when my trusty laptop decided to give up the ghost. After giving me no problems at all for 3 1/2 years, it just abruptly froze and refused to reboot (while I was on a trip, of course). After a couple of frustrating days of waiting for the computer guys to look at it, the report came back that the mother board had died, so I've got an order in for a brand new, retina display, high end MacBook Pro. It's my work machine, and they only replace them every 4 years, so I always try to get the very best I can buy because in 4 years it will be massively obsolete. In the meantime, I've resurrected my ancient Core 2 Duo and a loaner i5, both of which are horribly slow and which required a couple of days of moving files and installing software before I could really get back to work.

So back to the comet.  This was my first night out trying to use these old laptops to run my imaging session. I knew VMWare+Windows 7 would be slow on either of these laptops, because neither has the solid-state drive I've become accustomed to. I tried both the Core 2 Duo and the i5 and had massive problems with both of them hanging and not connecting to my USB cameras and USB-Serial connector. Eventually I got the older machine, the Core 2 Duo, working, found the comet, and started imaging. I guided on a star, but kept having problems because the USB transfers from the cameras were slow so the guiding would keep pausing. I never did get the i5 to work right, but eventually (when I switched targets to the Helix Nebula) I stopped the Core 2 Duo and rebooted both the host and guest operating systems. Things ran fairly smoothly after that, but I can't wait for my new machine to get here so I can really put things right.

If I had this to do over, I would use a focal reducer and no filter. The proper motion of Jacques is pretty large (I understand it was at minimum distance from Earth about the time these images were taken), so a shorter focal length would make my optics faster and I could also make my subs longer because the motion would not be as apparent. As it was, I was limited to 60 seconds; any longer, and the nucleus was clearly blurred. I'd also try to guide on the comet nucleus rather than on a star; I think my guide camera is sensitive enough it would probably work. The UHC-S filter probably was not the best to use with a comet. 

I had all kinds of fun trying to stack the comet images. I first tried Deep Sky Stacker, which has a comet stacking option. You have to select the comet in each subframe, then you can stack on the comet only (streaked stars), on the stars only (no comet), or on stars and comet (both sharp, but essentially this does two passes and superimposes the images). The stars+comet option is what I wanted to use, but it has a bug in that it messes up the color. I tried separating the R, G, and B and stacking separately, then recombining in Photoshop. That works, but is a massive pain and kills your resolution. So finally I stacked on the comet nucleus only in Nebulosity (translation only rather than translation+rotation, which I usually use). I post-processed in StarTools pretty much in my normal way, just with less stretching. This picked up a little bit of tail.  Here it is:

Date: 28 Aug 2014
Subject: Comet C/2014 E2 (Jacques)
Scope: AT8IN
Filter: Baader UHC-S
Mount: CG-5 (Synta motors, PicGoto Simplificado)
Guiding: 9x50 Finder/Guider+DSI Ic+PHD 2.3.0 (Win 7 ASCOM)
Camera: DSI IIc, chiller at 2.50 A, 12.5 °C
Acquisition: Nebulosity 3.2.1
Exposure: 47x60 s
Stacking: Neb 3, bad pixel map, extract NEB, normalize, de-Bayer & square, trans align on comet nucleus, 1.5 SD stack
Processing: StarTools 1.3.5.289 Crop; Develop 74.99%; Wipe; Develop 55.61%; HDR: equalize; Color: scientific 300%; Track: 7.2 pix. Photoshop CS6 Astronomy Tools levels, AstroFrame.

After that I switched to the Helix Nebula. As the nearest known planetary nebula to the Sun, it has the largest angular size and is one of my favorite objects to image; some call it the "Eye of God" because of its appearance. Finding the Helix manually has always been a bit of a challenge in the past because there aren't any nearby bright stars to use in positioning my Telrad finder. But amazingly, I was able to get Cartes du Ciel and the PicGoto to work on the old computer and this time I just synched on Fomalhaut and the goto was right on. My guiding performance was very poor; I guess I should have paid more attention to balancing my mount for this part of the sky. Overall, I was happy to pick up some of the outer shell of the nebula (in the upper left part of this image), but I'm sure I can do better and get a sharper image if I guide better. This would also probably be a good H-alpha target.

Date: 29 Aug 2014
Subject: NGC 7293, Helix Nebula
Scope: AT8IN
Filter: Baader UHC-S
Mount: CG-5 (Synta motors, PicGoto Simplificado)
Guiding: 9x50 Finder/Guider+DSI Ic+PHD 2.3.0 (Win 7 ASCOM)
Camera: DSI IIc, chiller at 2.50 A, 12.5 °C
Acquisition: Nebulosity 3.2.1
Exposure: 47x300 s
Stacking: Neb 3, bad pixel map, extract NEB, normalize, de-Bayer & square, trans+rot align, 1.5 SD stack
Processing: StarTools 1.3.5.289 Crop; Wipe; Develop 75.13%; HDR: equalize; Color: scientific 249%; Deconvolute 2.4 pix; HDR: optimize; Life: moderate; Track: 2.2 pix; Magic: shrink 2. Photoshop CS6 Astronomy Tools several cycles of layer mask space noise reduction; lighten DSO; more noise reduction; levels, AstroFrame.