Comet C/2021 A1 “Leonard”

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I woke up at 2:15 AM on December 7th and headed to Custer Institute and Observatory in Southold, NY (there are too many trees to the East at home). I set up to the Southeast corner of the sheds, in an attempt to block the strong, cold Northwest wind. It was almost completely overcast.  So I waited.

Around 4:55 AM a small hole in the clouds developed around the comet and lasted 50 minutes.  That was all I needed to capture Comet C/2021 A1 Leonard and its very long tail:

I was also able to see the comet and a small portion of the tail, pointing up away from where the sun would soon rise, through my 15×70 Celestron SkyMaster-Pro binoculars.

C\2021 A1 (Leonard) is an inbound long period comet discovered by G. J. Leonard at the Mount Lemmon Observatory on 3 January 2021 (a year before perihelion) when the comet was 5 AU (750 million km) from the Sun. Jupiter’s orbit (5 AU from the Sun) is at the frost line where methanol (CH3OH) and water start sublimation. This is the first comet discovered in 2021 and has a retrograde orbit. On 12 December 2021 the comet will be 0.233 AU (34.9 million km) from Earth and on 18 December 2021 will be 0.028 AU (4.2 million km) from Venus. It will make its closest approach to the Sun on 3 January 2022. Its magnitude was approximately 5.2 on December 7th.

I made a simple time lapse of Comet C/2021 A1 Leonard, including passing clouds, satellites, and a meteor.  I left it all in, with no editing.  Not my best work, but it is still fun to watch how fast this comet moves across the background stars. And the speed of the comet makes presenting a “frozen” image (that is, both the comet and the stars not streaking), an interesting task.

Moving faster can actually help, as you can reject pixels, through statistical stacking, the same way you would “remove” a satellite or airplane from a set of individual images. This is the comet “frozen” and the stars streaking, which reveals the long tail a little better than the previous image, where both the stars and comet are frozen.

You might be able to see the tail better in the monochrome reverse-color image:

Image Capture Data:

  • Date and time: December 07, 2021, 4:55 AM to 5:45 AM EST
  • Location: Southold, NY
  • Telescope: Borg 90mm, f/4 doublet fluorite refractor
  • Camera: ZWO ASI 183MC cooled to -15C
  • Integration: 45 x 60 seconds.
  • Conditions: 5 Celsius with nearly overcast skies, except around the comet for 45 minutes
  • Transparency: 1/10 for most of the sky, but 5/10 to 8/10 near comet
  • Seeing: 2/5 with strong winds