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Hunting for Meteors in Your Night Photos

The standard procedure for photographing a meteor shower is to photograph as wide a swath of the night sky as possible all night long. With modern digital cameras, this usually means setting a camera to shoot 15-30 second exposures at around ISO 1,600, with a 2-5 second pause between frames, resulting in a night’s haul of more than a thousand frames! While this photography can be fully automated, allowing you to sleep overnight, the real work of finding the meteors in your shots starts in the morning! We’ve cast our fishing net out, and now, it’s time to haul it back in to see what we’ve found.

Of course, we’re all hoping to catch a really bright meteor, so the first task is to do a quick scan of our shots. If you’ve followed my earlier recommendation on taking the photos (Tips for Photographing a Meteor Shower), you should now have a collection of JPEG files along with your raw files. The smaller JPEG files should load quickly with any decent image browser. Be sure to view the files in full-screen mode, relaxing your eyes to take in the full view of your screen as you page through the shots. Any truly outstanding meteors should jump out at you.

Finding the Needle in the Haystack

Sadly, most nights will yield only dim meteors, making it necessary to take a closer look at your images. For this task, a more capable image browser/editor/organizer such as Lightroom is required. With Lightroom used as the tool, here’s a list of steps:

  • Import the shots into Lightroom.
  • Pick a shot from the middle of your sequence and adjust settings (brightness, contrast, sharpening) to maximize visibility of dim streaks. Don’t worry about the aesthetic appearance of the shot for now.
  • Apply (sync) the settings of your selected frame to all of the night’s shots.
  • Step through all of the frames again in a full-screen view using the left/right arrow keys, marking frames with meteors with a flag of your choice (e.g. rating 1 star). For a close look at a questionable streak, left-click the image to zoom in temporarily.

Eliminating the False Needles

One thing you will certainly find is that the sky is covered with streaks of light: airplanes, satellites, lens flares from passing cars, and perhaps even a real meteor! It’s important and often not easy to be able to identify what you see. These days, many media stories about meteor showers appear with photographs that are clearly not meteors, with some going so far as to add random lines to a night photo! Don’t add to the embarrassing bad shots out there! 

So, how do you recognize what is and isn’t a meteor? It’s sometimes easiest to start with what is not a meteor:

  • Lens flares: With really wide lenses, a passing car in the corner of the frame could make a visible transient lens flare, usually on the opposite side of the frame and often dimmer and of a different color. Since the light source is on the ground, this means the lens flare will appear in the sky portion of the frame. This will vary with different lenses, so your experience with your own lenses counts here.
  • Aircraft: These streaks of light are often bright and obvious. Red, green, or white lights on aircraft make it fairly easy to pick out, especially if they follow a curved path across several frames. Use a magnified view to confirm this. A trail of colorful dots may result from the flashing lights on the aircraft.
  • Satellites: These can vary from very bright (brighter than Venus) to barely visible in your shot. Irregular bright knots of light in the trail may be visible as different flat surfaces of a satellite catch sunlight. These can be distinguished from meteors because the trails are colorless (just sunlight reflections), and they are slow-moving. If you are shooting with, say, 20-second frames plus three seconds between frames, if a trail is visible in more than one frame, that is probably a satellite. Catching the same trail in three consecutive frames clearly indicates a slow-moving satellite. Low-earth orbiting satellites are most likely to appear within an hour or two of sunset and sunrise. Check the website (or app) for Heavens Above to see just how many satellites are visible from your shooting location.

Once you’ve eliminated the false alarms, you have a real meteor shot! These should have some color to them, caused by the heating of the meteor to incandescence as well as the ionization of atmospheric molecules. If the meteor is really bright, be sure to check the frames after the meteor appears. You may have also caught an ionization trail lingering in the upper atmosphere. These can last for several minutes (appearing on several of your frames) and twist into interesting shapes, depending on the upper-level winds.

Sorting the Needles

When you’re out to shoot a particular meteor shower, although the meteors can appear anywhere in the sky, their paths should trace back to a specific area of the sky called the radiant of the meteor shower. This radiant is typically not well-defined and covers an area several times larger than the moon. Think of an orbiting cloud of dust that we, on the spinning Earth, in our own orbit, are running into.

However, we can still get some curveballs thrown at us. There are often multiple meteor showers in progress at the same time, though typically at a much lower rate than our targeted shower. And there are truly random meteors, though at an even lower rate. These will appear at odd angles and have different radiants compared to what we expect for the targeted shower.

Presenting Your Meteor Shot

Because meteors will appear virtually anywhere in the sky, even a frame with a bright meteor will probably end up having to be cropped for framing. Dimmer meteors will require even more cropping in, so a camera with a high-pixel count is best.

In some meteor showers with a high rate of meteors, making a composite may be an attractive final product. However, if you’re shooting with a camera on a fixed tripod, wide-angle lens distortion and movement of the sky are problems. Ideally, a program such as PTGUI should be used to map each individual frame (after applying lens corrections) to the inside of a sphere before the frames are composited. But in many cases, simply using Photoshop is adequate with the following steps:

  • Choose a base frame, usually in the middle of the collection of frames to be composited.
  • Open the frames as layers in Photoshop, with the base frame in the bottom layer.
  • Disable visibility of all layers except the base and the layer to be adjusted.
  • With transparency set to about 60%, manually adjust the frame using the Free Transform tool (Edit > Free Transform, or ctrl-T). Rotate, translate, and scale the frame so that the stars closest to the meteor match the base frame as closely as possible. Don’t worry about matching stars far from the meteor track.
  • Set the transparency of the updated frame back to 100%.
  • Add a mask to each transformed frame, allowing visibility only for the meteor trail (black mask everywhere except for the meteor streak).
  • Adjust the color and brightness of the background adjacent to the meteor trail in the transformed frame to closely match that of the base frame.
  • Repeat the processing for each meteor layer.
  • Once all transformed layers are ready, turn on visibility and set them all to blend using Lighten mode.

An alternative to a composite shot is to turn your night’s sequence into a time-lapse movie. If you have a typical haul of 1,000+ frames, you can turn this into a 20-30 second clip at the cinematic rate of 24 frames per second using just Lightroom and Photoshop:

  • Assuming you have your frames in Lightroom, make your aesthetic adjustments (color, exposure, etc.) on a typical frame in the sequence, and sync the adjustments to all of the frames.
  • Crop the view down to a suitable aspect ratio (usually 16:9) and sync this adjustment to all frames.
  • Export the frames as JPEGs into a subdirectory or other empty directory, downsizing the frames to a video-compatible frame size (e.g. 3,840×2,160 for 4K, or 1,920×1,080 for HD).
  • Start Photoshop and use File > Open, navigate to the exported files, and click on the first file in the sequence. Then, click on the check box which says Image Sequence. Photoshop will then ask you for the desired frame rate (use 24 frames per second), and then open all of the images, placing them into a video Group. You may have to explicitly use Window > Timeline to open the video editing window below your image view.
  • To create the video file, use File > Export > Render Video to open the dialog window to set the video options such as where you want the output placed and the format you want. I stick with the relatively standard H.264 encoding in MP4 file format.

Above is an example of a Perseid meteor shower time-lapse movie (August 2020). Meteors flash by in a single frame (watch carefully), while aircraft and satellites are visible in several consecutive frames.

Consolation Prize Options

It’s unfortunately common to come back emptyhanded when trying to photograph meteors. But don’t just erase all of your files. You can still create an all-night time-lapse movie. If you had clouds blowing through, this enhances the drama of the night sky.

If you had clear skies during your meteor drought, consider creating a star trail composite from your frames. Hint: These look best if you remove the airplanes from your frames.

At the very least, it’s a warmup to practice your skills in sorting through your frames and post-processing for the next meteor shower. The Perseid meteor shower in August 2021 is a good opportunity, as the moon phase is favorable this year, and this is one of the more active annual showers.

— to fstoppers.com

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