Last week, I went out to photograph the comet NEOWISE before it disappeared. I had never seen or photographed a comet before, and it far exceeded my expectations! I filmed my process along the way, including several tips for star photography (and of course comet photography too).
Here’s the video, which we just published on YouTube:
I’ve gotten questions about how much image quality improvement this stacking technique can produce. Technically there’s no upper limit, but the idea is that each time you double the number of photos that you stack (i.e., 2, 4, 8, 16, 32, 64, and so on), you’re going to improve your image quality by about one stop. Because I stacked 53 images in this case, it’s about 5.7 stops of image quality improvement over a single photo. Because my single photos are at the high ISO of 16,000, the final image works out to be roughly equivalent to ISO 320 in image quality.
If you prefer the visual explanation – who wouldn’t!? – here’s a comparison between a single image and the final stack (with heavy noise reduction applied to the single image):
It’s a massive difference, and these aren’t even 100% crops. Image stacking (or a star tracker) is the way to go when you need to shoot any deep-sky astrophotography subjects.
One thing I mentioned in the video but also want to point out here is that the bluish-green bit at the bottom of the comet is called the “coma” (not to be confused with the lens aberration coma in photography), and it’s actually the comet’s atmosphere! One of my main goals was to capture that in a photo, and I almost jumped for joy when the final image stack showed it so clearly.
If you want to photograph NEOWISE too, you’re definitely running out of time, although it should still be visible about 1.5-2 hours after sunset if you can find an area without too much light pollution (and you live in the Northern Hemisphere). Bring binoculars! Finding NEOWISE should still be pretty easy; it’s a bit below and to the left of the Big Dipper. But it’s getting dimmer each day now, and before long you’ll only be able to see it with your camera or binoculars, and not the naked eye.
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