Capturing the International Space Station: An Astrophotographer's Guide to Tracking and Imaging

A recent triumph in astrophotography showcases the power of dedication, specialized equipment, and open-source software in capturing stunning celestial events. The International Space Station (ISS) was recently imaged during an impressive 80° high pass near Cape Canaveral.

The Setup and Process

The remarkable feat was achieved using a combination of high-quality gear and meticulous processing:

Telescope: 11" Celestron NexStar GPS
Camera: Blackmagic Pocket Cinema 4K
Barlow Lens: 2.5x Luminos
Software: Open-source SatTraker software

The tracking process was detailed by the astrophotographer: "SatTraker gets it in the finder camera right away. I only did a 1 star alignment and a rough bubble level of the tripod, but that's enough to guarantee it will be in the 50mm lens finder camera I use. Then I just click on ISS as soon as it gets above the trees and the telescope centers up on it, even with a 2.5x barlow and a camera with a 2x crop factor (micro 4/3rds format). I calibrate the finder camera with the 'calibrate camera' button after clicking on a star before tracking the satellite. It moves the telescope in declination until the star has moved 100 pixels and then calculates how far the telescope had to move to displace it by that amount. Then during tracking I use the arrow keys, if needed, to adjust the centering in the main camera frame. Usually just a single keypress here or there is good enough if it starts to drift to one side of the frame. The program doesn't talk to the main camera though, just the finder camera, I'm just checking the main camera visually in a separate window."

Image Processing

After acquiring the raw footage, the processing steps were as follows:

Export: 10 frames were exported from Davinci Resolve.
Stacking: The frames were then stacked in Registax.
Sharpening: Wavelet sharpening was applied.
Cropping: The final image was cropped.

Exposure Settings

Optimizing exposure is crucial for capturing the ISS. The astrophotographer noted, "I usually start at about 1/250th of a second at ISO 8000 and go down or up from there. When the sun is on the opposite side of the sky from ISS, reflectivity is high so I drop it down to 1/500th or even 1/1000th. When it gets to the same side of the sky as the sun, the panels are dimmer so I raise it back up to 1/250th or even 1/120th of a second."