Spectacular Views!
Comet Tsuchinshan-Atlas C2023 put on quite a show in October! This was the best comet I've seen since Comet West in 1976.
On October 12th the comet had just recently swung around the Sun and was predicted to appear close to the horizon shortly after sunset. I had previously searched for an observing site with an unobstructed horizon and found a nice one overlooking the James River about a 10-minute drive from my house. I arrived shortly before sunset to use the setting Sun as a guide because the comet would appear closely above the sunset point. The following wide field sunset image was taken at 6:31 pm EDT.
As you can see above, sky conditions were unusually clear near the horizon. At 7:19 pm EDT I took the next twilight image capturing Venus on the left and the comet on the far right, both having nearly the same 6.67-degree height above the horizon. (Enlarging the image makes the comet easier to see.) In the photo a portion of the comet tail shows up even in bright twilight, but, on October 12th, I had a hard time seeing the comet with the naked eye.
In the next image I isolated just the comet alone from the previous picture.
On the next evening, October 13th, the comet was higher in the sky after sunset. When I saw clear sky conditions, I decided to see if the comet would be visible from a corn field within walking distance of my house. It was a relatively mild evening with temperature in the upper 60's, so I didn't bother to exchange shorts for long pants. I hurried over to the corn field taking a shortcut through about 200 meters of grassy field. This brief journey over grass had unexpected consequences! I later discovered both ankles covered with chigger bites! Several days of itchy discomfort followed.
As I took pictures with my Nikon Z6II mosquitoes attacked in a dense cloud. They constantly brushed my bare legs and face, and their high-pitched whine buzzed past my ears. While working the camera I danced around swatting my legs while pulling a light jacket over my head. At home afterward I discovered legs and socks covered with bloody spots where I had crushed mosquitoes. Miraculously, I managed to avoid mosquito bites. The chiggers were another story, however.
In spite of the insect assault, I did manage to get some images on October 13th. The following picture was taken at 7:37 pm EDT when the comet was 7 degrees above the horizon and faintly visible to the naked eye.
On October 14th the southwestern sky was hazy, but the comet was higher in the sky. This evening the comet was clearly visible to the naked eye even in the presence of moonlight. Once again, I journeyed to the nearby cornfield, appropriately clad in long pants to avoid the previous night's insect disaster. The next image is a 6-second exposure that shows some corn field foreground and approximates the actual naked eye view.
There are two interesting things to notice in the previous October 14th images. First, the anti-tail pointing downward just below the bright comet head is faintly visible in each picture if you enlarge and use averted vision. I needed darker sky and less moonlight to make the anti-tail more visible. Second, look roughly halfway up the comet tail to see two star-like objects within the tail itself! (Once again, enlarge the images to see this better.) The object on the left is the star 5 Serpentis, and the object on the right is globular cluster M5! Of course the comet tail is very much in the foreground with the star and globular cluster far away behind it! The comet was 4 light minutes away, 5 Serpentis was 82.8 light years away, and M5 was 24,000 light years away. This was a chance alignment of three unrelated objects along the line of sight. Here is a magnified picture of 5 Serpentis and M5 captured on March 13th, 2024 with my Seestar 50:
On October 15th globular cluster M5 was next to the comet's head! It would have made a great picture with my Seestar, but the sky was completely cloudy, and comet observing was impossible.
Although clear sky returned on October 16th, the nearly full Moon now became a problem. Moonlight washed out the tail in the next pic taken at 7:34pm EDT when the comet was 18 degrees above the horizon.
Enlarge the next labelled image and notice star 5 Serpentis and globular M5 below the comet head. By comparing this October 16th image with the October 14th image (where the distant pair were behind the tail) you can see how far the comet moved relative to the stars in two days.
The comet was higher above the horizon on October 17th. It would have been seen against darker background sky under moonless conditions, but, unfortunately, the nearly full Moon's brightness cancelled the comet's higher altitude advantage. Nevertheless, in spite of a streetlight directly in the line of sight, I could see the comet from my front porch. Instead of making the long trek to my cornfield observing site I set up my camera on the front porch to capture the next image at 7:54pm EDT when the comet was about 17 degrees above the horizon. The comet now looks slightly dimmer than the previous October 16th image even though I doubled the 16th's ISO value for this 4-second exposure.
The incredible string of cloudless evening skies continued on October 18th. This night I discovered a new observing site in a field only an 8-minute walk from my house. Better yet, the 8-minute walk was entirely on paved surfaces avoiding chigger infested grass on the way to the corn field! The Moon rose a bit later than the previous night and was slightly less full. The next image shows the comet about 24 degrees above the horizon. It was taken at 7:31pm EDT with the same camera settings as the October 17th image .
I wondered if this was a rocket launch from Wallops Island on Virginia's Eastern Shore, but could find nothing online about such a launch on October 18th. Later at home, when I inspected a Sagittarius/Milky Way image taken at 7:34pm EDT, I noticed the strange feather-like object exiting on the image's extreme lower left edge. (You need to enlarge the picture to full size to recognize the object on the very edge.)
I searched for other possible October 18th rocket launches and discovered Space X had launched a Falcon 9 rocket with 20 Starlink satellites aboard from Cape Canaveral on October 18th at 7:31pm EDT! So I had, indeed, observed that Space X rocket launch! From the Sagittarius/Milky Way pic I could see it originated in the southeast. So it couldn't have been a launch from Wallops Island in the northeast. I only wish I had seen it sooner! If I had taken the Milky Way pic a few seconds sooner, I might have caught the rocket closer to image center. I couldn't get the camera in position fast enough to get better subsequent pictures. Still, this was an awesome sight to behold!
Incredible as it seems for southeastern Virginia, the sky was completely clear again on October 19th! This evening I tried something different. I took my Seestar to the new nearby observing site. It was worth the effort because Seestar produced the following comet image with a 2-minute exposure.
The entire comet tail was too large to fit within Seestar's field of view. Due to its orbital motion during the 2-minute exposure the comet drifted slightly relative to background stars. The comet head is slightly smeared out by this drift, but not too badly during two minutes. Longer exposures reveal more tail detail, but the comet head then becomes trailed into a straight line instead of being the point-like object it truly is. For example, look closely at the comet head in an enlargement of the following 5-minute exposure. You can see the head elongation.
On October 20th I took a day off from imaging. Then it was clear yet again on October 21st. Once again, I walked over to my favored observing site carrying the tripod-mounted Nikon. The Moon had not yet risen and the comet was higher in the sky. In spite of these advantages, the comet had dimmed so considerably that I could barely see it with averted vision. After struggling for some time to find the comet in the camera viewfinder I managed to get the following image at 7:38pm EDT when the comet was about 28 degrees above the horizon.
The sky is noticeably darker and the comet noticeably dimmer than previous photos with identical camera settings (4 sec at ISO 3200 with a 70mm f/2.8 lens).
After October 21st the comet faded significantly. I could no longer see it with the naked eye. On October 28th the comet's orbit brought it near distant globular cluster NGC6426. In spite of scattered hazy clouds I thought it might be worthwhile to capture this close encounter with Seestar. This time I hauled a beach chair to the observing field so I could control Seestar more comfortably. The best picture I managed to get between drifting clouds was the following 3-Minute exposure.
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Dim globular cluster NGC6426 is visible to the lower left of the comet head. Once again, this is a chance alignment of unrelated objects. The comet was 7.26 light minutes away this evening and NGC6426 was 67,000 light years away far behind the comet!
Clouds and increasing moonlight put an end to comet imaging. Perhaps I'll try again with Seestar near new Moon sometime in November.
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