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Mike Olason

Location of Photo:

Tucson, Arizona

Date/Time of photo:

4 August 2021, 0910 UT


11" SCT and STF-8300M CCD Camera


Comet C/2020 S3 (Erasmus) in these images appears to have 2 tails. The comet was magnitude 16.7 with a coma 40" wide and was 298 million miles from Earth. The main tail extends beyond the field of view of these images to the right of the coma and in the images is 0.2 degrees long at a position angle of 257 degrees from the coma, this tail is at least 0.03 degrees wide. The second tail is only 80 arc seconds long (0.02 degrees) and is above and to the right of the coma at a position angle of 319 degrees, it is a thin tail which shows best in the 2 insets at the lower right of the images. Yes, the tails are faint in these images. Comet C/2020 S3 (Erasmus) brightened to magnitude 3 as seen in SOHO images when it reached perihelion in it's refined 2588 year orbit as it passed 37 million miles from the Sun in December 2020. The comet made it's close approach to Earth in November 2020 at 96 million miles and it was observed at magnitude 5 before being lost in the Sun's glare last December. It appeared out of the Sun's glare in the morning sky this past spring at about magnitude 15 with a much brighter and slender tail as can be seen in the 20 May 2021 image submitted to Sky&Telescope earlier this year. There did not appear to be a second tail at that time.