It was the last two nights of the year and I had clear weather. What luck!
So, on Friday night, Dec 30th, I had to take care of unfinished business with the Horse Head from the last session. I had something to block the parking lot lights from next door this time. While waiting for the Horse Head to get into position, I took images of M33 (above,) which I hadn’t tried with the AT60ED, yet. It came out decent, I guess.
While taking the Horse Head, I noticed on the charts that a comet was in the field. It was C/2017 K2 (PANSTARRS), at magnitude 11.9 according to Cartes du Ciel.
I imaged until almost midnight on Friday. I left the mount setup and brought in the rest with plans to try again on Saturday, New Year’s Eve.
On New Year’s Eve, my plans were to go for M78. While it was getting high enough, I got some more data on the Heart Nebula – an hour and six minutes. I mixed it with the salvaged Heart job from a couple of months back at about 22 percent to help fill in some noise.
When I got going on M78, it gave me problems with tracking. I finally realized it was my guide calibration and after redoing it, I was back in business, but wasted almost an hour figuring that out. Consequently, by the time the clouds came at about 10:20 PM, I still had less than 2 hours of data. Oh, well… I’ll try again next year! lol
On Wednesday afternoon, Dec 20th, 2023, it was clearer than predicted. So, I broke out the scope and setup to catch the first quarter moon and test a filter I purchased last year that I only used twice.
My main problem with using this filter was getting my flats to work when using the QHY294C camera. I was never really successful last year and I had to manually do flat calibration in FitsWorks, which was a pain. So, my first step was to get a good flat and hope that it worked with the 3 minute exposures I planned to use.
Conditions that evening were predicted to be clear, but only average transparency. In actuality, it was average to below average with a few high clouds that came in periodically. Oh, well… I was not expecting to get any keepers this night, but I still wanted to test that filter.
The Antlia Triband RGB Ultra filter, a lower cost triband filter that I had mixed results with at a dark location last year, was what I wanted to use and test from my heavily light polluted metro area location. It would be the first time to try it in this kind of heavy LP.
So, the first image at the beginning of the post is how the UHC-S filter performed with 9×3 minute subs. The conditions were better when this image was taken, so keep that in mind.
Next, here’s how the Antlia Triband RGB Ultra filter did with roughly the same exposure on a below average night:
Almost a match for how much nebulosity it picked up, but the key differences are the star halos that the UHC-S filter tends to produce on bright stars and the lack of halos for the Antlia filter, plus the much stronger blue channel with the Triband.
Next, I put it to a real-world test with 50 sub-images of the California Nebula:
I noticed during the acquisition of these that the filter was performing really well, and my flat was working reasonably well. It was not perfect, but good enough for what I intended to accomplish.
I have a second version of the processing using a PS Starless action. Not as clean as a removal as StarNet++, but it’s very fast!
After this, I wanted to try it on the Horse Head and Orion Nebula. I started on the Horse Head, but didn’t get too far because my scope was starting to point directly at the parking lot lighting next door. Once the light was directly hitting the lens, that was it. So, only 4 sub-images were good out of the dozen or so I took.
I opened the stack in FitsWorks while still imaging it and cropped out the bad part that had caught the direct view of the streetlight. I spent only about 5 to 10 minutes fussing with it in FitsWorks, which has very limited image editing tools. It came out much better than I anticipated:
Here’s the same image, but it is the uncropped, full-field. I worked on it in PSCS3 to repair the damage from the streetlight’s strong gradient in the top left corner and do a better processing job than what FitsWorks does:
So, my conclusions are this filter, with a good flat, tends to work better in heavy LP than the UHC-S filter. Mainly because it doesn’t produce bad halos around bright stars. But, it is also because it has a great blue channel, unlike the UHC-S. That sure makes color balancing easier and I can go after broadband targets in addition to just nebulae.
BTW, I never did get a shot of the moon that night. The filter test results were too good and I didn’t want to waste any time that I could otherwise use to test it on more nebulae.
It was a very clear night after a cold front had passed and enough time had gone by for the winds to calm down again. I setup before sunset and got ready.
The Moon was out and in conjunction with Saturn, which was right above it. Unfortunately, the field of view was too narrow to include both in one frame without rotating the camera to another angle. So, I just shot the moon
I composited together an overexposed shot and the first image and blended it to show the moon among a few stars. Not quite what I was hoping for, but you get the idea.
The Pleiades is one of those images I end up with when I want to kill time while waiting for what I really want to image. In this case, it was the Seagull Nebula, which was my main target for this session.
I maxed out for one night with 4.5 hours on this object, which when added with the session from last week, gave me nearly 6 hours on the Seagull. Finally, an amount of time that gives very smooth results – once you add them all together properly.
The only serious image out the bunch was the Soul Nebula. It was the only one I planned for and was my main target. I managed to get 3.8 hours on it, with .8 hr on one side of the peer and the other 3 hrs on the other. BTW, all images were taken with a QHY294c, a UHC-S filter and a AT60ED on a SkyWatcher GTi goto mount in Bortle 7-8 skies.
The rest of the images were mostly done with 30 sec exposures at high gain (i.e., 3000. I normally keep it at 1600.) Like I said, I was sightseeing and doing an EAA experiment.
The Elephant’s Trunk Nebula area was the longest of the 30-sec shots, 240 x 30 seconds. I still had to combine it with about 30% blend of a 90 minute exposure taken with another camera, but the same scope. It was still too noisy even after 240 subs.
So, the 30 sec high gain experiment for EAA type imaging is not up to par with what I could do with the QHY183c camera. It did well on open clusters, at least. Oh, well. Live and learn, as they say.
Images of Comets, Nebulae, Galaxies and Star Clusters