Comet NEOWISE has been hanging around in night skies around the world for a little while now, and most photographers who have been blessed with clear skies have captured at least one shot of the comet. Beyond getting a good exposure, how do you process your astro shots for the best effect? In this tutorial, I'll show you how I edit mine.
Astrophotographs are hard to edit because they're dark and noisy. Low light means long shutter speeds and high ISOs are needed to get a balanced exposure of the stars, and that goes for photos of Comet NEOWISE, too. We all know what a field looks like at midday, and that sunrises and sunsets are golden and rich with warm tones. However, it's difficult to get a handle on the right color balance for night shots. That's mainly because of how our eyes work.
In our eyes we have two types of light cells: rods and cones. The cones aren't very sensitive to light, so require a lot of it to work. But they are capable of recognizing color. Whereas, the rods — more sensitive to light — aren't very good at color.
In fact, head outside tonight and you'll see that things are quite monochromatic. That's why it's hard to judge how to process night shots — because we're not used to seeing the light and landscape in great detail. But there are a few things that can help, so let's take a look at how I edited my photograph of Comet NEOWISE appearing above Stonehenge, in England.
1. Shoot in Raw
2. Reduce the ISO Noise
Comet NEOWISE has great definition in its tail, and when it's dark you can see the huge length of it, and the split in the middle from where it got boiled going round the sun. So it's best to capture it with a relatively fast exposure of just a few seconds. That means ISO has to be boosted up high, but with high ISO comes noise. This is the same when shooting during a new moon (i.e. when the moon isn't shining in the sky) the scene is noticeably much darker than when the moon is out. That's when I find myself boosting the ISO up high. But with that comes dreaded ISO noise, which can spoil an otherwise excellent photo, with its gritty bad looks.
3. Remove Light Pollution With White balance
That's because this white balance is designed for the warmer interior lights you'd find in your home, so it drops the white balance low to around 3,000 K to compensate and keep colors looking natural (when compared to daytime shots). That's exactly what it does here, enhancing blue and purple, and reducing orange and yellow. I recommend shooting in raw format so that you can tweak this after in editing software, and that's because I sometimes prefer to adjust the Tint slider to remove the excess magenta that's associated with both white balance presets.
4. Produce Better Contrast
5. Enhance Star Detail
6. Enable Lens Corrections
I'll also tick Enable Profile Corrections to counteract the lens distortion and vignetting characteristics because I want an accurate, undistorted astrophoto. Then, if I want some of that vignetting back I'll either add some Post-Crop Vignetting in the Effects panel, or just use the Radial Filter with the Exposure slider turned down to -10.
7. Boost the Colors
8. Make Several Versions for Comparison
I use the Snapshot feature in the Develop module of Lightroom Classic to do just this. Click the + button in the Snapshots panel, name it and click Create. Then make your adjustments and do the same again to save another snapshot. Now you can flick between the two to compare the edits.
9. Compare Multiple Similar Shots
There's no right or wrong way to process astrophotography shots, unless you're doing it for scientific purposes, but even then NASA false-color images. Experiment with the above until you find what suits you. Sometimes a little more yellow suits the scene, and other times it looks best cool and blue.