Watching Comet NEOWISE

On July 20 and 21, I was able to take the telescope out and try catching Comet NEOWISE. Weather has been a challenge in Boston Metro West, but it cleared out enough to let the comet be naked-eye.

The coma and tail looked clearly visible through binoculars and the telescope. I was especially surprised to notice the greenish color of the coma through the telescope on July 20. Before heading out on July 21, I setup the 12mm eyepiece with the camera adapter to try capturing a glimpse of the comet with an Android phone. And it worked!

The image shown in this slice is one of the photos I took. You can see the star HIP49576 on the left at apparent magnitude 9.28 (flipped horizontally by diagonal mirror). The comet looks way brighter than the star at about 3.5 or 4th magnitude. And what I keep finding most interesting is how easy it is to distinguish the green color of the coma, visually and on the photo.

The green color is said to be caused by light emissions in high concentrations of cyanide (C-N) and diatomic carbon (C-C) molecules present in the sublimating gases, which are being energized (excited) by the ultraviolet radiation of the Sun.

Comet NEOWISE imaged from Norfolk county in Massachusetts on July 21, 2020 at 21:26 EDT. Image taken through a Nexstar 6SE, with 12mm eyepiece, and a Moto G7 Power smartphone at 3/10 sec, and ISO of 26334. HDR+ using 100 frames and EV +2.0. No additional post-processing.