^{Last Updated: May 2, 2021}

Phil McGrew had an out of this world idea. Capture the International Space Station as it hurtled across the face of the pre-dawn moon.  Great Idea – because it worked! How we figured out when and where to be to make this happen is described in the references below.

We agreed to meet at a spot that fell near the “blue line” (centerline) of the event: Muir Beach Overlook.  I woke up at 3:00 AM and arrived there at 4:45 AM. Everyone showed up on time at 5:00 am and we lugged our equipment into the conveniently located World War Two era machine gun bunkers which kept us out of the wind. There were 3 such bunkers and I took up residence in the closest one since I had the most gear to haul (and am the most lazy).

My companions picked two other bunkers, while Rick headed further North along the coast highway.  Note: Don’t let the term Highway confuse you it is a tortuous winding road hanging on sheer cliffs above the Pacific Ocean.

 

Resources and References

• ISS Predictions (Includes the Android tool from Ed Morana, and another web based tool)
• ISS Transits by Ed Morana
• Prediction Tool by Ed Morana
• ISS Real time track (Nasa)

Notes about the Event

Before we left we had some discussions about whether the ISS would be visible and how to prevent it from “streaking” and smearing. The ISS is moving at  17,800 miles per hour. At its altitude from our location, that means it crosses the ½ a degree wide moon in under two seconds! At minimum I needed to select an fast enough shutter speed to max out the camera’s frames per second (more chances to get at least ONE hit) which on the Canon 50D is about 5.3 fps.  However we weren’t sure about the comparative brightness of the ISS compared to the moon.  If it were sufficiently dimmer then the moon brightness would overwhelm the ISS.

It’s interesting to try to get the ISS against both the lit and unlit portion of the moon – and we indeed got both.  The ISS trajectory and where you choose to go affects what you will see.  One of our group went farther north and got the ISS brushing the lit edge of the moon, though not crossing it.  This proved to be a quite interesting shot as it is definitely true that the ISS does not stand out well against the moon.

I went with about f/9. This is a rough calculation factoring the f/7.5 refractor  [80mm aperture with 600mm focal length], and a 1.4 teleconverter.  I had to tape over the pins on the camera-teleconverter or it would not let me take the shot “cannot communicate with lens” well – duh, the lens in this case is a TELESCOPE.  ISO 800, speed 1/500th of a second and the camera in BURST (continuous high speed exposure) mode.

We were not expecting a whole lot but were all high fives and thumbs up afterward.  Now that I’m groggy from sleep deprivation I’m wondering if driving about 4 hours round trip was worth 3 seconds of glory.  Yeah, I think so.

If you’re interested in catching the moon near your favorite STATIONARY object, I’ve got a well reviewed, well attended webinar on that.  Want to try some Astrophotography? I’ve got webinars and field shoots for that, too.  Join me and let’s do something unusual with night and low light shots.

For the latest predictions for the San Francisco Bay Area, Yosemite National Park, and Research Triangle North Carolina see this page.