Comet 41P was the main target I was after for my imaging session on the night of Friday/Saturday, April 21/22, 2017. It has gotten further away from Earth and is therefore smaller, but it is still relatively bright. I wanted to get it before it gets any smaller and dimmer.
It is still in the northern skies and circumpolar and thus visible all night. I still had to wait for it to get high enough and out of the combined LP domes of Abbeville and Lafayette, LA to the northeast. Transparency was only so-so this night and the LP was really noticeable. Very humid, too. Temps were in the lower 70’s/high 60’s during the night, so the camera was on the warm side. The seeing was pretty good this night, however.
I shot 2 dozen images (about 2hrs worth) and only had to throw away one. My mount got stuck again while tracking and I had to shake it loose. The image that was finished right afterwards was no good due to that. I think the overhaul of my mount is long overdue. Another project that I really need to get done. lol
Here is Comet Johnson again from a relatively dark site. I did not devote much time to it since it was not my primary target this night. It is only a little over an hour of integration. Perhaps it was a little too warm to use 5 minutes/ISO 1600 for exposures, at least with this low number of sub-images. But, I didn’t want to have to shoot two sets of darks, so I stuck with one exposure length all night long.
The month of April 2017 is turning out to be really good for comets. So far, 4 photogenic comets are all vying for my attention. On the morning of April 8th, 2017, I got a chance to capture images of Comet PANSTARRS (C/2015 ER61) for the first time. It was a short imaging session due to moonlight interference and the comet rising only high enough to image shortly before sunrise.
Too bad it was short, since I also wanted images of Comet Lovejoy. It was just north of Comet PANSTARRS and I visually spotted it in 15×70’s binoculars. But, by the time the sky and comets got right and the exposures looked good, it was already 5:17 AM. Astronomical twilight was starting at about 5:30 AM. So, most of my shots ended up having either moonlight interference or twilight interference. Doh! 🙂
I could only get so much out of the two stacks I ended up with. At least it was something. I also tried out some new stuff and that was a plus. An update to my planetarium pointing software allowed me to tell PHD2 Guiding to move the mount with the comet instead of the stars. It worked somewhat. At some points the tracking was only so-so and I had to throw out a couple of subs But, I needed to try it to find that out.
While waiting for another comet to rise high enough to start shooting, I took a few shots of Comet Johnson even though the moonlight was strong in that area and I wasn’t expecting to get much. Surprisingly, the comet shows up with a slightly diminished tail, but the head and coma show well enough.
I did not spend much time on it and was not going to bother processing the data at first. The colors and dim areas suffered, but not enough so that it couldn’t be fixed somewhat. Lucky for me. 🙂
Terry Lovejoy’s newest comet is in outburst and has brightened quite a bit above what was expected of it. Now, it is a really nice comet in the dawn skies. Unfortunately, it is moving fast and quickly heading lower and lower to the horizon with each morning. So, the good viewing window is short and sweet.
I had to wait for it to clear a roof and it was already after 10:30 UT (5:30 am CDT,) so I had to shoot it between the start of astronomical twilight and nautical twilight. Plus, this is from a Bortle red/white zone, so I had lots of LP to contend with. Not the best conditions, but hey, at least I got a usable image.
Taken from a Bortle Red/White zone, this image is 40 sub-images of 120 seconds each at ISO 800. This is double than what I was able to do before. The inclusion of an IDAS-LPS drop-in filter for my Canon T3 allowed this one stop of extra exposure. So, now I know how much the drop-in filter blocks, which is quite a bit.
Regardless of the above, the gradients and the color shift from removing that much LP still make processing difficult and tedious. I am glad I can drive just 30 minutes and get to a spot dark enough to be camera noise limited instead of skyfog limited. It is such a joy to process images that have low LP levels. 🙂
Here’s one I haven’t shot in a while. I was using it as a test to see how bad the LP would be. Not long after this was taken, Comet Lovejoy was in the same general area LP-wise, so I had a pretty good idea how much comet I might get.
Here’s a quickie of Comet Johnson. I took two test images before the automated run, which I ended up using. But, I was pretty tired by the time I got to this one, so I let it shoot automated while I took a nap. Unfortunately, the guiding got screwed up after only 11 sub-images and I didn’t shoot more of it after I woke up since it was near sunrise and I needed to shoot calibration data for my other stuff instead. Oh, well…
Images of Comets, Nebulae, Galaxies and Star Clusters