Capturing Neowise 2020

July 22, 2020  •  Leave a Comment

The TravelerThe TravelerComet (C/2020 F3) (NEOWISE), over Butte, Montana, July 14, 2020. July 2020 seemed occupied by tracking and photographing Comet Neowise as it swung by the earth and sun. In defiance of fears that it would disintegrate, the comet came from behind the sun and became visible to our eyes.

I ended up taking a lot of photos (trust me, you will never see most of them) and in the process learned more about how to capture images of celestial objects, while preserving smooth, blue, night-sky gradients.

It seems to be troublesome: 

  • You want stars as points of light, so you cannot push your exposure too long. Yet you need to capture enough light to populate magenta, purple, blue, and cyan (the likely colors in the sky) in your capture. If you don't, the sky may become posterized (or banded).
  • You want to control sensor noise -- so you cannot push your ISO (sensor sensitivity) TOO high.
  • You need sharp focus -- so something somewhere that is bright enough to set the lens at infinity is necessary (auto focus will likely not work, so you must focus manually).
  • You want a pleasing composition -- context for the comet (the horizon or another object) really helps.

To create this image, I aligned five images (each taken at ISO 3200, f5.6, and 4 seconds) to sharpen the comet and control sensor noise. Keeping the sky smooth was difficult, because that part of the image was still short on the information needed to produce its colors. Increasing the ISO and/or lengthening the exposure would likely have helped.

I like this image because I managed most of the exposure issues and captured some detail in the comet's tail. However, the endmost parts of the tail likely extend off the image to the right. I wish I had moved the comet a little to the left and down so that it didn't crowd the right side.

On the bright side, I have lots of time to learn more about night sky photography; Neowise is not scheduled to return for about 7,000 years. I might have it down by then.




No comments posted.