Comet NEOWISE

Comet C/2020 F3 NEOWISE

The comet became circumpolar for us on about July 14 or so, and on the 17th we had a nice clear night to shoot all night. This time-lapse begins at about 9:00pm and runs until about 4:30am on July 17/18. I took about 1700 frames with a DSLR and a wide-angle lens all on a pan tilt head, which moves across the horizon following the comet. It shows the comet setting just after sunset, then it skirts the horizon, and rises into the dawn. As the comet skirts the lake, you see its reflection in the water. I used the same exposure for the entire sequence, so the brightness changes of the comet are due to its lowering and rising in altitude. One can imagine a rope attached to Polaris as the comet swings above the horizon, pendulum-like. There were three or four ISS passes on the night and I captured at least two, along with planes, satellites, fireflies and even ATVs on the other side of the lake. A little airglow near the end of the night put some colour in the sky just before dawn.

NEOWISE

When I got there, there was still hope that it could clear off so I set up and started the timelapse. Despite the increasing clouds I let it run away on the off chance that the cloud might reverse itself, and well, thats what you want in a timelapse. Although that did not happen, I captured an ISS transit, a little bit of the comet rising when the clouds were thin, and a lovely, colourful sunrise. I chose a 5 second interval, and I started the sequence when the comet was at about -3 degrees, hoping to catch the tail rise. The settings at that time were iso 5000 and 3s exposures @ f/2.8. I leave a 2s gap for processing. The camera has to send a jpg to the iphone/app for analysis via wifi, then the app may adjust the settings and send the camera new instructions in that 2s gap. As the dawn progressed those settings were adjusted to keep the same brightness per frame, ultimately ending up at exposures of 1/2000s iso 500 and f/3.5 (still being taken in 5s intervals). I took my Honda generator down to the lake, its fairly light and quiet. Mark helped me a lot with Orienteering. But at the end of the day I used an app called Spyglass to determine my camera position vs the horizon. I noted that when the comet was at -3 degrees altitude it was at 19 degrees azimuth. And the field of view of my camera/80mm lens is 24 degrees x 17 degrees. 19 +24 = 43 so I took the easy way and put the right edge of the frame at 45 degrees east, with a little foreground but mostly sky.