SUNSET: 
0
Photographer:
Mike Olason
Location of Photo:
Tucson, Arizona
Date/Time of photo:
4 August 2021, 1124 UT
Equipment:
11" SCT and STF-8300M CCD Camera
Description:
These images show Comet C/2021 O1 (Nishimura) on August 4 one day before it's close approach to Earth on August 5 when the comet will be 158 million miles from Earth. The skies were clear which was a good thing since the images had to be collected above the eastern horizon in brightening morning twilight. The images showed a visible comet coma at least 0.03 degrees wide and a fan tail to the west of the coma. The software calculated a magnitude of about 9 for the comet in the clear skies. The image insets to the right were computed by Astrometrica which used stars visible in the images to calculate the magnitudes and position of the comet for the times shown in the insets, G is the calculated magnitude for each inset image. The comet will reach perihelion in it's orbit on 12 August 2021 when it will be 74 million miles from the Sun.
