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How to Find, Photograph, and Process an ISS Pass

Photographing the ISS

Photographing an International Space Station (ISS) flyover is not as difficult as it may seem.

You don’t need fancy imaging software or top-of-the-range photographic equipment. All that’s required is a DSLR & lens, remote shutter control or intervalometer, sturdy tripod, free stacking software (or whatever your software choice may be), and some patience and planning.

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…and of course a good working knowledge of your camera!

Finding the ISS

Start by researching when the ISS will be visible over your area, and familiarise yourself with the coordinates and other information supplied.

You can find out about sighting opportunities in your location on websites like www.heavens-above.com or  spotthestation.nasa.gov.

Heavens Above

Once your observing location is selected on heavens-above.com, you’ll be presented with ISS pass details.

Definitions

Brightness / Magnitude
How bright the ISS will appear. The brighter the object, the lower the value. Our sun is magnitude -26,74; full moon is -12,92; and the bright star Sirius is magnitude -1,47.

Start / Highest point / End
These are the details about the pass will start, where it will be mid point and and where it will end. By using this information you can calculate where the ISS will appear and frame your composition.

Time / Alt / Az 
The exact time it will pass through the Alt (altitude: degrees above the horizon) and Az (azimuth: the direction, SouthEast or NorthWest, etc.) Note that if a pass is low (maybe 20 degrees and below), it might be obscured by surrounding houses and trees.

Some ISS passes are short, others long. Take note of how long the ISS will be visible in the sky before it passes into the earth’s shadow, that can help compose your framing.

Photographing the ISS

Look for interesting foregrounds, maybe a tree or building, or impressive night landscape. Be careful to not choose something that emits too much light (like streetlights or a fully lit house), as you’ll have the shutter open for a few seconds gathering light, and wouldn’t want to blow the photo out.

Set up a little while prior to the pass to take some test shots. You need to find the right exposure settings before the ISS comes around.

To capture the ISS you’ll need to take a series of photos on the flyover to layer into 1 final photo, not one continuous photo (with the bulb function of your camera)

Why? Layering the exposures give you more control over lighting the foreground and composition. Depending on your location and environent, it may be ideal to have an 8-15 sec exposure length for each exposure.

ISS Flyover
Photo: Tanja Schmitz

1. Frame your shot.

Including terrestrial objects are visually more interesting.

2. Take a series of test exposures.

The settings will be location dependent.

Keep your aperture setting low to allow your lens to collect enough light.
Example: If you have a lens of F/4 then you might want 12-15sec exposures. Shooting at F/2,8 will be 10-13 seconds.

Shutter Speed: 10-15 seconds, depending on your surroundings.
Continuous shooting enabled, and use your remote shutter release pressed and locked in to have the camera continuously taking exposures.

ISO: Location dependent, 400-800 in urban skies and 800-3200 in dark skies.

Capture to RAW and small Jpegs for quick previews.

White balance set for your location.
Daylight WB is too warm. Try a custom setting anywhere from 3500 – 4500, it will all be dependent on the amount of light pollution in your shoot location. However, if you intend to work with the RAW files you can change this in post production.

TIP: If the moon is out, you’ll have to shoot multiple shorter exposures to not over expose the landscape.

3. Focus!

Don’t forget to focus! Use the stars to focus on.

A popular technique is to test with setting focus around the infinity mark. Take short exposures after making tiny changes to the focus ring, and zoom in at highest magnification on the LCD to see which focus is the sharpest (autofocus and lens stabilisation should be switched off).

Once you’re happy with the composition and amount of lighting in your image for the shutter speed you have selected – you’re ready to go!

The ISS is always on schedule

Initiate your shooting before the arrival time, you can always delete unused frames. Keep shooting until the ISS pass is completely finished or you’re 100% confident it’s out of view.

If you want a well-composed, correctly-lit, impressive ISS pass, be prepared to spend time testing out various aperture and exposure settings.

Processing your ISS images

You’ve captured an ISS pass, and now you’re sitting with a bunch of photos that look like a whole lot of nothing.

The goal is to combine all these photos into one, and you do that by “stacking” them on top of each other, the same method is used to create star trails.

We’ve documented 2 ways of stacking an ISS pass. One using freeware called StarStax and another in PhotoShop. 

Preview your images and delete the frames prior and post the pass so that you’re only working with relevant photos.

Before you start

If you’re familiar with editing/opening RAW files you can adjust white balance, exposure, etc., prior to stacking. Make the changes you want to your RAW images, and then output them to JPEG to be stacked.

editing the ISS
Editing the ISS single frames in Lightroom

Option 1: Stacking In StarStaX

  1. ISS Stacking in Star Stax
    Stacking in StarStax

    Open / drag and drop your images.

  2. Select start processing. By default the settings in preferences should be set to blending mode: lighten. If your photo does not look like expected, make sure to revert back to the default settings.
  3. Once the stacking process is done the finished stacked file is displayed. Save the stacked file (File / Save as).
  4. Take your final image and adjust further light, contrast and saturation if required in your image editing software of choice.

Option 2: In PhotoShop

  1. ISS Stacking in Photoshop
    Stacking in PhotoShop

    Open all the image files

  2. Cut and paste each photo into into the same image file, layering all the photos on top of each other.
  3. Select all the layers and set the blend mode for each layer to lighten.
  4. Once stacked you can either save a JPEG, merge all the layers down or even add adjustment layers to your image for colour/saturation etc.

With all the effort placed in capturing and stacking your images, take care to edit the finer details!

The ISS photographed through trees
Photo: Tanja Schmitz
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About the author

Tanja Schmitz

Tanja is the co-founder of PhotographingSpace.com with her husband, Cory. She is also the co-owner of several telescopes and Celestron mounts, too many cameras, and not enough hard drive space.

An internationally commissioned and published astrophotographer, her work has been used in multiple online and print publications. Tanja was also shortlisted for the Astronomy Photographer of the Year award.

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