Full frame:
With galaxy season upon us, it was time to try out my AT8RC at its native focal length of 1625mm (f/8). My plan was to use the TS Flat 2 that I got as a flattener for my Stellarvue 80 and use that on my AT8RC. I calculated that the spacing I required was right around 111mm from the TS Flat 2 to the sensor. I first tried this out on Messier 51 back on the 7th of March. The results were mixed. Star shapes looked good in the corners but the seeing was rather poor and as a result it was hard to judge whether the combination was sharp or not. The color data for this came from last year. Last years version was sharper but not as smooth. Here is what the stars look like in the corners. That is much improved compared to not using a flattener. Skies again cleared on the 15th of March, and I decided to go after a MUCH tougher target, Arp 83 (NGC 3799 and 3800). Seeing started out poor at the beginning of the night but improved steadily as the night went on. I ended up with 35 luminosity subs (10m binned 1x1) and tossed 15 of them, keeping only those with a FWHM of 3.0 or better. It cleared again on the 17th of March and I got 11 more luminosity subs, nine of which I kept. My best sub had a FWHM of around 2.1 which is my best ever for luminosity. Sharpness is definitely improved over what I could get working at 1190mm with the CCDT67. I also picked up 4.5 hours of color data on the 17th. Full frame: Annotated: Crop around NGC 3799 and 3800: Animated GIF of at least two asteroids in the field. (42920) 1999 SA8 is to the right and is the more obvious of the two. Much fainter is (123336) 2000 VD45 and is located well above NGC 3800. I'm really pleased at the detail I was able to resolve. NGC 3800 is the larger and brighter of the two at magnitude 12.5 and 2' x .6' in size. NGC 3799 is magnitude 13.7 and is just .7' x .5' in extent.
0 Comments
With the Moon still mostly out of the way on February 23rd, I decided to go after Arp Galaxy 336, also known as the Helix Galaxy, and NGC 2685. I had attempted to get color data on it earlier, but the seeing was horrible, with high clouds moving in and out making the data next to useless.
This night started out far better with excellent seeing, and the tracking on my MyT mount performed the best it has so far. It may have helped that I turned down the setting on the dew heater. Although I imaged through the night, it turned out high clouds returned for the 2nd half, again making those subs unusable. But the first 19 ten minute subs binned 1x1 in luminosity were good. Here are three versions. The first is a full field and is annotated. The 2nd is just the field. And the third is a 800x600 crop showing the detail in the galaxy itself. This is an example of a polar ring galaxy, a type that is fairly rare. It has a ring that is perpendicular to the disk of the galaxy. While rare, they do occur with some frequency (I've seen mentioned around 5%) with lenticular galaxies. There is lots of other unusual structure as well. The cause of these galaxies is not well understood. "And it's something quite peculiar, Something shimmering and white, Leads you here despite your destination, Under the Milky Way tonight" (Church, Under The Milky Way). These lyrics were so appropriate last night, but not really in the way I think they were originally intended. The Moon was out of the sky early, but there were high clouds that were fairly dense. Things were shimmering way too much, and the clouds were way too white. Given the conditions, I decided to go after one of the Messier objects that was still missing from my collection, Messier 93. This is a star cluster located in Puppis in the deep Southern skies (almost -24 degrees declination). I did image it very close to the time it was transiting the meridian. Tracking with my mount was absolutely horrid regardless of where I was in the sky. I'm not sure if that it because of the poor conditions with the clouds, the seeing, or problems with the mount at what were very cold temperatures (2F or -16.66 Celsius) or some combination of them. Fortunately star clusters do not need long integration times and in fact, you can often get better color and separation from the background by using shorter exposures. Total integration time was just 27 minutes (9 minutes each color channel with 1 minute subs binned 1x1). Since subs were short, the diffraction spikes that I like in such images were very subdued. I added some using Carboni's actions.
Another 1.5 hours of luminosity data was gathered the night of February 15th together with several hours of color data. I published an initial version of the luminosity data on Astrobin, and then reprocessed it based on some suggestions from Hytham (Thanks!). I also used a different form of noise reduction (MLT) instead of my usual (TGV Denoise). While I prefer to do my noise reduction as my last step, in this case, I have to say that MLT did a much better job of it. Rick over on Cloudy Nights pointed out that ARP 94 is not the only train wreck in the image. Much smaller and further away galaxies PGC 30397 and PGC 1605532 are also interacting. If you look closely at the image, you can see a tidal plume headed to the left from the upper portion of PGC 30397. Here are luminosity, color, and annotated versions: The natural course of things when you get new equipment is to be blown away with how wonderful it is. Then you start finding some issues. And finally, you begin to learn how to deal with those issues.
With my Paramount MyT, I began to notice that although my tracking was normally very good, RA guiding was considerably worse near the Zenith. One night it was so bad I was getting RMS errors of as high as 1.5 arc-seconds. That is completely unusable when you have an image scale of .93 arc-seconds like I do with my AT8RC and the CCDT67 reducer. My AT8RC is not completely neutral in balance because the off axis guider is somewhat off center to the left, the stepper motor for the Moonlite is to the left, and worst of all, the 50mm finder I used for a while before I got my OAG was also to the left. For the most part the Atlas dealt with that amount of in balance just fine. However, the MyT is best when completely in balance. I removed the finder and rebalanced. Fortunately, when tested RA guiding was quite good. The Arp galaxies are fascinating in the many ways these galaxy groupings interact. Arp 94 in Leo doesn't seem to be imaged all that often by amateurs and I'm not sure why. Perhaps it is because of its proximity to Gamma Leonis. Perhaps it is because everyone seems to focus on the much more famous nearby Messier objects such as Messier 65 and 66. Whatever the cause this set of galaxies is certain interesting. This is 23 subs of 10m each binned 1x1 for a total of 3 hour 50 minutes. Tazer on Cloudy Nights clued me into the really nice annotation capabilities in PI. For some reason, it does miss a few bright PGC galaxies in the field, especially the one above Arp 94. Finally, I have added two more hours (2 sixty minute subs in Ha binned 1x1) to my image of Sharpless 2-224.
I have been going after Sharpless 2-224 when I can. This time of year I only can get a few hours each night. I knew this was going to be a tough one going in. It is in category IV in my Interstellarum Deep Sky Atlas, and honestly, I'm very surprised it is visible at all visually. Here is what I have so far after 3.5 hours. I need to update this since I do have another hour of data. I'm using 30m and 60m subs. A much easier target is Messier 53. Star clusters are good candidates for imaging when the Moon is up since they aren't quite as affected as galaxies and reflection nebulae. This is 3 hours 55m of data in LRGB using 5m subs binned 1x1. Both these objects were imaged using the AT8RC riding on the MyT.
"Cold-hearted orb that rules the night,Removes the colours from our sight.Red is grey and yellow white" (Moody Blues, The Day Begins).
Many amateur astrophotographers have a fear of the Moon that goes beyond reason. Sure the cold hearted Orb does make imaging more difficult. But imaging is still possible even during a full Moon. At this point, you may be thinking that I'm about to wax poetic about narrow band imaging. Actually, I'm not. With enough persistence and integration time, it is quite amazing what can be captured even with LRGB. To make my point, the luminosity in the following image was taken when the Moon was roughly 96% illuminated. (February 2nd, 2015). The color was taken near new Moon, but that is just because it was what I had sitting around. Color data can be taken during Full Moon as well. Would this image have been better if the luminosity data was taken during New Moon? Of course, but why waste could clear sky time? I think much of the fear of the Moon is a leftover remnant from imaging with film. There it WAS much more difficult to deal with. Luminosity data is 34 subs of 10m each binned 1x1. I grabbed 2.5 hours of Ha data (30m subs binned 1x1) on the Jellyfish Nebula, IC 443 on the 28th of January. I grabbed 3 hours of Ha data (30m subs binned 1x1) on the California Nebula, NGC 1499 on the 31st. I also took nine 1 minute subs binned 1x1 of each color channel for a total of 27m integration time. Total time was 3 hour 27 minutes. In both cases I used my Stellarvue SV80ST-25SV riding on the Paramount MyT.
"And the seasons they go round and round" (Circle Games, Joni Mitchell) Galaxy season is soon approaching. By 1 or 2 in the morning, I'm finding I have to switch over to galaxies. And some galaxies like Messier 81 and Messier 82 are well positioned fairly early in the night. So I've been shooting them recently either as secondary (Leo Trio, Markarian's Chain) or primary (Messier 81 and 82) targets. In the meantime, and just as importantly, I'm getting used to using my MyT mount. It continues to perform very nicely and I'm just real impressed with it and the integration with TheSkyX. First light using my Paramount MyT was Messier 65 and 66 in Leo. But I still haven't gathered all the data needed to actually produce an RGB image of them yet. I have gotten the data for Messier 78 in Orion. I'm not finished with this one yet, in fact I'm gathering Ha data for it as I type this. Here is what I have so far. I'm very pleased with the Paramount MyT so far. Together with TheSkyX Pro it is a very powerful combination. Pointing accuracy has been excellent, especially after running a TPoint model (right around 10 arc-seconds with my Stellarvue SV80ST-25SV). Measured periodic error was 3.3 arc-seconds. That is well below the advertised maximum of 10 arc-seconds. Using the altitude and azimuth adjusters for polar alignment is a pleasure instead of a pain as it was with the Atlas. It normally frames to within one pixel of correct in SGP and it guides really well too. It is really nice having the homing feature to get to a known orientation. The through the mount cabling has been really nice.
I am still waiting for the WiSky module since Software Bisque got a bad batch of them. Fortunately, they caught it in internal testing. |
Archives
March 2020
Madratter
Here are my occasional thoughts on Astrophotography, Astronomy, and whatever else catches my attention. Categories |