airplane trails

How to tell the Difference Between Planes, Satellites and Meteors

Look! Up in the sky! It's ...

Sometimes, you just want to know what kind of object is passing through your star trails or star stack. Why? Could be for any reason, but the most obvious is that in post-production you might prefer eliminating one type of streak in the sky while not eliminating another. Or, you might just be curious.

Fear not, astral observer and recordist! I will guide you in how to identify and classify plane trails, satellites and meteors.

Planes

First up! The bane of of my existence. Plane trails. (I’m just kidding. Without those wonderful airplanes, I couldn’t go to all these wonderful places!)

Plane trails are easily identified by the following characteristics:

  1. They are almost always solid lines with hashed or dotted lines on either side.

  2. They travel at a predictable rate, often spanning many frames in an exposure stack.

  3. Usually, they travel in a predictable path. But, they are not always straight! You may see course changes that curve away from the initial heading.

This example spanned six frames:

Nikon D750 with a Zeiss 15mm Distagon f/2.8 lens. Six exposures at 30 seconds, f/5.6, ISO 6400.

Want to eliminate plane trails? See “4 Ways to Remove Airplanes from Star Stacks.

Satellites

Satellites are even more fun to identify, and tricksy like Hobbitses. You may want to think they are meteors, but they aren’t! Here’s what to look for:

  1. Satellites are very thin and often dim paths with no other markings alongside.

  2. In my experience, they move slower than planes, and so they also can span more than one frame in a star stack.

  3. The trails from satellites are solid lines that are the same brightness from one end point to the other. They do not taper in and out like a meteor (keep on reading for details).

This example spanned ten frames:

Nikon D750 with a Zeiss 15mm Distagon f/2.8 lens. Ten exposures at 30 seconds, f/5.6, ISO 6400.

If you want to know with certainty (or get notifications) when a satellite or the International Space Station is passing overhead, there are a ton of apps for that. See this article from Space.com for a couple of suggestions. Lance uses Sky Guide (iOS only) with great success.

Meteors

Meteors are the “holy grail,” right? We all want some meteor love in our frames. Here is how you discern meteors from the other sky objects mentioned above:

  1. Meteors taper in from nothing or a very thin path at the start point and taper out again at the end of the path.

  2. They move faster than planes and satellites, and thus often appear in only one frame, possibly two (depending on your exposure length).

  3. They can be many different colors, depending on if they flare up during entry.

  4. They almost always appear in only one frame, because they move fast and burn out quick!

Here’s an example of a whole bunch of meteors at Great Sand Dunes National Park, shot during the Perseids:

Great Sand Dunes National Park, Colorado. Nikon D750, 15mm Zeiss Distagon f/2.8 lens. 234 images at 22 seconds, f/2.8, ISO 6400, plus a single exposure at 382 seconds, ISO 2000 for the landscape after moonrise.

Iridium Flares

Bonus! There’s something else those night streaks might be. Iridium flares.

Iridi-what, you might ask? Yeah, I kinda asked the same thing when Gabe and Lance mentioned them to me while looking at the photos I pulled for this post.

Iridium flares are the reflections from a certain set of communication satellites with highly reflective antennae. When they line up properly with sunlight streaming past Earth, they glow while traveling through the night sky for up to 20 seconds.

In a photo, they look much like a meteor—a long, bright streak with tapered ends. But because they last much longer than a meteor, their trails can appear longer, and can even last through multiple frames (as in the stacked image above—you can see the gap from when the shutter was closed). Here’s another example:

Nikon D750 with a Zeiss 15mm Distagon f/2.8 lens. Two exposures at 30 seconds, f/5.6, ISO 6400.

Alas, as cool as these can be to shoot, they won’t be shooting through our skies much longer. Iridium, the company that put them up there, is taking them down. For more info, see their brilliantly titled “#Flarewell” webpage.

Wrapping Up

Now that you know which is which, I hope deciding which to eliminate or enhance will become easier during your post-processing.

Stump the Chump

Got a mystery? Post your photo (either in high resolution or cropped close to the object) in the comments section or on our Facebook page and I’ll help you identify it. I’m looking forward to sleuthing out some mysterious sky events with you.

Matt Hill is a partner and workshop leader with National Parks at Night. See more about his photography, art, workshops and writing at MattHillArt.com. Follow Matt on Twitter Instagram Facebook.

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4 Ways to Remove Airplanes from Star Stacks

When I make a star stack sequence, I’m at a crossroads for my editing choices.

Do I remove the plane trails? If so, do I live with the tiny gaps in those star trails left behind by the removal process?

It’s a hard decision. On the one hand, the journalistic approach is, “That’s what happened in front of my camera—it’s the truth.” If that’s your creed ... you’re done! Make whatever levels and color adjustments you want and move on.

But when I desire to have a final image without plane trails, I spend some time to make sure it’s done right, and that I’m making a quality photograph.

Want to learn some techniques on how to do this? Is there a method—without having to be a professional photo retoucher—that doesn’t leave gaps? Read on, my fellow night photographer.

Note:

If you are unfamiliar with how to create a star stack, see these previous blog posts:

Prep: How to Find Which Layers Have Plane Trails

I used the same image stack for all the demos below. Shot in the Fruita Orchard of Capitol Reef National Park during our workshop in June 2018.

Gear:

Exposure details:

  • 63 images shot at 30 seconds, f/5.6, ISO 6400
  • total exposure duration: 31.5 minutes

I knew I wasn’t going for star points, so I chose a 30-second exposure to keep long exposure noise down in the high desert summer heat. The temps weren’t that bad, but I wasn’t taking any chances.

For expediency, I exported full-resolution JPGs from Lightroom to Photoshop. Stacking TIFFs straight from Lightroom with this many files can really choke a computer. As it was, the PSB file was 4.2 GB when saved.

Note:

Do not apply lens profile corrections before making a star stack. It can lead to irreparable moire in the final stacked image. If you want to do apply lens corrections, do so after stacking and flattening.

How to Find the Planes

  1. Create your image stack in Photoshop and save as a PSD or PSB file (the latter when the file is over 2 GB—don’t worry, Photoshop will prompt you if it’s needed).
  2. Identify which layers have plane trails. But how, you ask?
  3. I like to turn on all the layers and apply the Lighten blend mode to each so I can see everything.
  4. Then I click and hold on the eyeball icon at left of each layer and drag downward in groups of ten or so, while staring at the image. This gives me kind of a faux animated preview of the layers being added one by one. (See video below.)
  5. If I see plane trail (or a portion of one) disappear, then I click the eyeball on each layer, one by one, upward from the bottom until it disappears. That’s how I know I found the offending layer.
  6. I make that layer a color to identify it for further work later.

An alternative way to do this is by revealing only one layer at a time, from top to bottom. Which strategy to use is just personal preference. Unless you’re on a PC, apparently. Chris is a PC user, and the trick I detail above and in the video doesn't work for him. What he does is group the layers ten or so at a time, changes the blend mode of all the groups to Lighten, then hides each group one by one, which helps him narrow down the locations of trails more quickly. Finally, he goes into the offending groups and finds the offending planes.

Either way, this process is time-consuming. So be patient. Find those planes. For the photo in the video below, the process above took me about five minutes. (I made it faster for you to watch.)

Note:

You may also find meteors and satellites in there. We have another blog post coming soon on how to identify the differences between them.

4 ways to remove plane trails in a star stack with Layer Masks

  1. Remove plane trails in a flattened image in Lightroom.
  2. Use the black paint brush in Photoshop.
  3. Use the spot healing brush in Photoshop.
  4. Use layer masks in Photoshop.

Which one is best? I am going to explore all four and compare them, so you can decide which works best for you. And, you can bet that I will have an opinion about what works best for me, too. ;-)

Removing Plane Trails in a Flattened Image

This is the fastest method, but also the least likely to be effective in terms of quality. If you must have it fast, try this first. If you don’t like the results, try one of the options that follows.

  1. Open your flattened image with plane trails in Lightroom.
  2. Select the Spot Healing Brush.
  3. Click once at the beginning of the trail. (See note below.)
  4. Hold Shift on your keyboard.
  5. Click once again at the end of the plane trail.
  6. Repeat for every plane trail on every layer.

NOTE:

You can paint freehand with the trackpad on your laptop (most awkward), with your mouse (somewhat awkward) or with a tablet like a Wacom (hardly awkward at all). This applies to subsequent techniques too.

I find that using keyboard arrow keys to move the healing brush target around is easier to manage than just using a mouse or trackpad. But it causes “jaggies” (below) more often than not, no matter how precise you are.

Using a Black Paint Brush in Photoshop

Since the Lighten blend mode for layers reveals the brightest pixels in a scene, painting with a black brush right on the image layer will make trails (which are bright) disappear.

  1. Select the Brush Tool with these settings: Opacity at 100 percent, Flow at 100 percent and Color at 100 percent black.
  2. Make your brush slightly larger than the width of your plane trail. (You may have to adjust this up and down, depending on the trail.)
  3. Paint over the plane trails. But only over the plane trails.
  4. Repeat for every plane trail on every layer.
  5. Merge layers or flatten when done with all.

Resulting image after using black brush to remove plane trails. Click to enlarge.

100 percent zoom crop to an area where a plane trail was removed.

In this video, I used the process of identifying layers first and then color-coding them before blacking out the trails. Even then, I discovered more along the way.

Note:

This is a destructive process. No going back. Unless you duplicate each layer you paint on and turn off the duplicate, but that increases your PSD/PSB size.

Using the Spot Healing Brush in Photoshop

I recently discovered this. While mucking about in Photoshop, editing my star stacks from Capitol Reef National Park earlier this year, I had a What If? moment. …

I asked myself, “What if I try using a different tool to remove star trails?” (I usually use layer masks, which we’ll get to in a little bit.)

  1. Select the Spot Healing Brush tool, and change the Type to Content-Aware.
  2. Make your brush slightly larger than the width of your plane trail.
  3. Click once at the beginning of the trail.
  4. Hold Shift on your keyboard.
  5. Click once again at the end of the plane trail.
  6. Repeat for every plane trail on every layer.
  7. Merge layers or flatten when done with all.

It works. I love this method, despite it being a destructive process.

Resulting image after using Spot Healing Brush to remove plane trails. Click to enlarge.

100 percent zoom crop to an area where a plane trail was removed.

In this video, I simply went from top to bottom to eliminate trails in each layer without color-coding them. I missed one plane trail, because I was kinda tired doing both back to back.

Note:

As mentioned, this is also a destructive process. No going back. Unless you duplicate each layer you paint on and turn off the duplicate, but that about doubles your PSD/PSB size.

Comparing the Methods

Let’s take a look at how the methods stack up against each other. (See what I did there?)

The edit in Lightroom of a completed, flattened stack? I immediately abandoned it. It was janky to complete, and undesirable:

And when your stars go the wrong way, it’s really hard to make it match:

So, all that’s left are the two competitors we’ve looked at so far. Below you can see the final images from each:

And here are some comparisons I made while viewing both simultaneously in Lightroom:

Above you can see that there isn’t really much difference between the two methods. At least in terms of image quality.

But … what did my time cost?

Painting Black

Pros: Easy to see if you covered a plane trail.

Using Spot Heal Brush

Pros: I just feel better seeing an image versus black lines all over. The trails are gone, and the layers still looks like a photograph.

Both methods have the same cons:

  • destructive to pixels
  • makes some gaps in the trails (thought remarkably few)
  • no way to go back on edits unless you duplicate your PSD/PSB beforehand

To Identify or not to Identify

I spent eight minutes identifying layers with stuff to eliminate.

I spent 30 minutes using the black brush on those layers I identified.

I spent 27 minutes using the Spot Healing Brush, layer by layer, without color-coding or pre-identifying layers.

It’s up to you which method helps you get through the process better. I can operate without color-coding in the future. One-by-one is the way for me.

Conclusion: Which Method Wins?

Guess what? Both strategies are just as effective. Yay!

And here is the proof: When gaps appear, they do so in the same places using both methods.

The above were from testing my own hypothesis that Spot Healing would work better. Surprise! I’m delighted to discover that for this test, both techniques performed the same.

Both methods create gaps. But you can meticulously fill them in with Photoshop prior to flattening. Use the clone tool, if you have the extra hours. ;-)

The Fourth Way—Using Layer Masks in Photoshop

This is how I’d always done it before my recent discovery. This method is non-destructive—if you save your PSD/PSB, you can always roll back the edits or modify them. (The downside, of course, is that an unflattened, many-layered file could be downright huge. If you’re not planning to save an unflattened file, this doesn’t provide much benefit.)

  1. Add a mask to a layer with a plane trail.
  2. Select the Paint Brush tool with these settings: Opacity at 100 percent, Flow at 100 percent and Color at 100 percent black.
  3. Make your brush slightly larger than the width of your plane trail.
  4. Click once at the beginning of the trail.
  5. Hold Shift on your keyboard.
  6. Click once again at the end of the plane trail.
  7. Repeat for every plane trail on every layer.
  8. Make your final contrast, color and other finish adjustments.

Give it a shot. You may like this better, especially if you are already masking out other things in your scene.

Et al.

Here are some examples of other stacks I’ve done using these techniques:

So go forth and capture, my fellow lovers of the night sky. And fear not the airplanes arcing across the heavens, for you can make their presence just a memory.

Matt Hill is a partner and workshop leader with National Parks at Night. See more about his photography, art, workshops and writing at MattHillArt.com. Follow Matt on Twitter Instagram Facebook.

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Finishing Touches: 3 Killer Post-Production Tips for Night Photography

In the whole history of photography, at least half the magic of creating images happened after the shoot, in that period of prestidigitation known as “post-production.”

In the film days, post happened in the darkroom, where many of us got stinky hands and forgot how to socialize with people who lived on the other side of the door in light. These days, post happens mostly on a computer, in which the millions of data points that make up our image are rearranged and altered in a way that produces the final photograph as our minds saw it in the field.

And when it comes to night photography, post-production tools can be used in all sorts of unique ways to help us seize the night exactly as we see fit. Below are a few of the techniques a few of us here at NPAN use to bring the image down the homestretch.

Working through post-production on a 27-inch  BenQ SW2700PT  monitor at our workshop in  Cuyahoga Valley National Park .

Working through post-production on a 27-inch BenQ SW2700PT monitor at our workshop in Cuyahoga Valley National Park.


Chris Nicholson

Making Planes Disappear

Remember when David Copperfield made a Learjet disappear on national TV? I do that trick too.

If you have photographed anywhere within the region of a major airport at night, or even just along major flight paths, then you know how conspicuous planes can be in an otherwise pristine dark sky. Many star trail photos have been bisected by plane trails.

Some photographers don’t mind that, and some do. Even among us five NPAN instructors you’ll find varying opinions. I, for one, don’t want planes in my sky shots, so I usually remove them in post-production.

Fortunately, Adobe has made this really easy to do, in both Lightroom and Photoshop. In the old days of digital darkrooms (as in, like, five years ago), to clone out a plane trail could take a fair amount of effort—it generally involved stamping over the offending pixels with the Clone tool while sourcing various other spots in the sky to avoid telltale digital artifacts, and then doing some cleanup work to make things look normal. But these days you can use the Spot Removal tool in Lightroom or the Spot Healing Brush (in Content Aware mode) in Photoshop to do most of that work for you.

But that’s not the tip, as many people reading this already know what a great job those tools can do to quickly and effectively remove unwanted elements of a photo. The tip is something that many photographers don’t know: You can draw a perfectly straight line with either the Spot Removal or Spot Healing Brush tools by shift-clicking on two points. This is enormously useful for quickly wiping out a straight unwanted element—such as an airplane trail in a night sky!

Simply zoom in on the airplane trail you want to remove, hold down the shift key, click once at one end of the trail, then once more on the other end. The trail will disappear from your composition, almost always without any artifacts to clean up afterward. It’s like magic. Like David Copperfield.


Matt Hill

Blending a dusk shot with star points

When you shoot on new moon nights, shadow detail is pretty hard to come by. One way to fix this—to add detail in the shadows, to mask high ISO noise and to add a “fantastic” sparkle to your image—is to blend in a photo that was shot during the tail end of dusk.

Of course, this requires patience. But trust me, it’s worth it.

Owachomo Bridge in  Natural Bridges National Monument , as photographed during our workshop there this summer.

Owachomo Bridge in Natural Bridges National Monument, as photographed during our workshop there this summer.

When I see the light turn that special indigo color, I set the camera on its tripod and go through all the motions of composing and getting ready for my night photo. Then, with twilight light still in the air, I shoot (in RAW, of course) one to three photos at a low ISO, with a white balance of Daylight, to faithfully render that delicate color.

Then I wait patiently until all twilight has left the sky (which happens faster if you face east) and then take a high ISO photo for star points, preferably with the Milky Way in plain view, and even better if the galactic core is in your frame.

During post-production, I cook the two images to taste, being careful to not accentuate the shadow details on the star points photo. Then I select the two images in Grid view, right-click one of the chosen thumbnails, and choose Edit In–Open as Layers in Photoshop. I put the dusk photo on the top layer, add a layer mask, and then mask out the sky (Figures 1 and 2).

Figure 1.

Figure 2.

Finally, I reduce the layer opacity to taste (Figure 3). I usually use anywhere tom 10 to 20 percent. The more you show, the more the final image looks more like fantasy. My ideal effect is to simply add a little sparkle to those dull shadows with color and quality.

Figure 3.


Gabriel Biderman

Creating and Saving a Milky Way Brush in LR

The great thing about our latest batch of digital cameras is how sensitive they are to light and how much better they can see than our own eyes. Take a look at the multitude of Milky Way photos populating the World Wide Web. Unfortunately most of them are a bit too over-processed for my taste. In their understandable enthusiasm, many photographers push the  Clarity and Dehaze sliders too far to the right so that every pixel is sharpened and we are seeing a very unnatural shift in the colors of the night.

A more subtle way to “treat” the Milky Way is by locally applying a gentle brush adjustment. I do my global adjustments and general processing first, but I do like the Milky Way to stand out a bit from the background of all the other stars, which is when the brush comes into play (Figure 4).

Figure 4.

To achieve this, start by clicking on the Brush tool and selecting a default Effect, such as Highlights. To aid me in seeing where I am brushing, I will generally adjust the brush to the extreme—like +100 highlights (Figure 5). Once I have brushed in the appropriate places, I start bringing back the effect and finessing the look.

Figure 5.

In Figure 6, you can see the adjustments I made to make the Milky Way, which make it pop a little bit more.

Figure 6.

That general separation between Milky Way and sky is created by adding contrast and clarity. I like to adjust contrast by not only using the Contrast slider, but also by raising highlights and lowering shadows. Clarity is a slider you need to respect though, as too much clarity creates noise and a halo effect along the edges of the contrasty regions of the image. That’s why it is so important to first apply any clarity and sharpening globally. Then you can really see how much, if any, is needed for the Milky Way.

Here’s the fun part—the real core of this tip. Those adjustments probably took a solid 5 minutes to make. But you don’t need to take 5 minutes to make them next time, or any time after that. Why? Because you can save those adjustments as a permanent brush that you can use at any time.

If you look at the top of the Brush panel, in the Effect drop-down menu, you’ll see an option called Custom. Click on Custom and a scroll-down menu of brush options will appear. Go to the second to last option and select Save Current Settings as New Preset (Figure 7).

Figure 7.

You’ll need to enter a title for your preset (Figure 8)—“Milky Way” makes sense, but you can call it whatever you want. Once you’ve entered your title, click the Create button.

Figure 8.

Now you have a Milky Way brush that you can paint onto all your dark sky shots! Any time you edit a Milky Way photo, make all your global adjustments first. Then select the Brush tool, choose “Milky Way” (or whatever you named it) from the Effects drop-down, and paint in your home-cooked adjustments.

Chris Nicholson is a partner and workshop leader with National Parks at Night, and author of Photographing National Parks (Sidelight Books, 2015). Learn more about national parks as photography destinations, subscribe to Chris' free e-newsletter, and more at www.PhotographingNationalParks.com.

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