Comet C/2020 F3 NEOWISE in the evening sky (Shallow Thoughts)

Comet C/2020 F3 NEOWISE in the evening sky

Comet C/2020 F3 NEOWISE continues to improve, and as of Tuesday night it has moved into the evening sky (while also still being visible in the morning for a few more days).

I caught it Tuesday night at 9:30 pm. The sky was still a bit bright, and although the comet was easy in binoculars, it was a struggle to see it with the unaided eye. However, over the next fifteen minutes the sky darkened, and it looked pretty good by 9:50, considering the partly cloudy sky. I didn't attempt a photograph; this photo is from Sunday morning, in twilight and with a bright moon.

Last night, Wednesday, it would have been higher, but it was cloudy here. Clouds are likely to skunk me tonight as well. I hope I get at least one cloudy, dark night to see it, because apparently it's developed a spectacular pair of tails, as seen in today's APOD. My northwest horizon isn't the best because that's where Los Alamos is, and although Los Alamos has a light pollution ordinance, it doesn't enforce it and the town's light pollution has been getting worse and worse (there's a newly formed dark-sky group hoping we'll be able to change that).

I've continued to tweak my comet.py script, adding a few minor features plus one major feature that came in very useful Tuesday night: the ability to print a table of altitudes and azimuths at fifteen-minute time intervals. So for instance, tonight I see:

Nautical twilight dusk
  2020-07-16 21:00 MDT     15°14'    318°45'
  2020-07-16 21:15 MDT     13°17'    320°21'
  2020-07-16 21:30 MDT     11°24'    322° 0'
  2020-07-16 21:45 MDT      9°36'    323°44'
  2020-07-16 22:00 MDT      7°51'    325°31'
  2020-07-16 22:15 MDT      6°12'    327°23'
  2020-07-16 22:30 MDT      4°37'    329°19'
  2020-07-16 22:45 MDT      3° 8'    331°18'
  2020-07-16 23:00 MDT      1°45'    333°22'
  2020-07-16 23:15 MDT      0°27'    335°29'

I used nautical twilight rather than astronomical twilight because this comet is bright enough to be visible in nautical twilight. Skyfield helpfully calculates all three twilights: civil, nautical and astronomical.

I'm keeping a text file on my website that I can check the comet's position from my phone or tablet even after I've shut my computer down for the evening: shallowsky.com/comet.txt. I'll keep it updated for at least the next week or until the comet fades. The times are for White Rock at 35.8° north; your times will be different if you're significantly farther north or south, or much closer to one edge of your timezone.

Also, if you want to play with the script but don't have Python installed on your own computer, Christophe-Gauge has adapted my script into an iPython Notebook for comet.py. I've mostly found iPython/Jupyter Notebooks hard to use, but one thing I didn't know about them is that you can use Google's Colaboratory to run a Python notebook from GitHub directly in your browser, without needing to install anything. That's the best argument I've seen yet for Notebooks. The Notebook is running a little behind my script (as I write this, he hasn't added the alt table output yet), but here's where you can play with it: Comet C2020 F3 NEOWISE Notebook on Colaboratory.