It took ninety minutes of sitting in the cold to get the shot. Every minute the camera took another exposure. Sitting on the summit ridge overlooking Keck, it was a very dark night with three lasers working the sky, Keck 1, Keck 2 and Subaru. The tripod was set up as close to the vehicle as I could get it to shelter the camera from the wind. Ninety minutes of shivering in the front seat of the truck, playing cribbage on my phone, and fervently hoping that the gusting wind was not shaking the camera enough to destroy the images.
The result was ninety frames on the memory card. When downloading the material I knew that my time spent in the cold at fourteen thousand feet had been worth it.
Material like this can be used a couple different ways. You can stack the images together to create a single shot equivalent to one exposure 90 minutes long. Taking single long exposures is problematic on a digital camera, a leakage signal called dark current will swamp the image. Better to take many short exposures and add them together in processing.
You can also play the images sequentially, creating a few seconds of video. In this case I assembled all ninety images as nine seconds of video when played at ten frames per second.
I found that the best single frame was assembled from only 23 of the original images. Keck 2 changed targets during the session, creating a confusion of beams over the telescopes when I added all ninety images. The 23 frame version is the definitive version that has been widely distributed. During this slice of time the Keck 2 laser was aimed at the galactic center in Sagittarius, the beam aimed right over me and the camera.
I released the photo as a PR photo for Keck, only fair as I had been on the mountain to work that night, taking the photo before driving down from the summit in a Keck vehicle. The PR folks have used the photo for a number of press releases and observatory literature including the 2011 annual report. You can even download it from the Keck website photo collection.
This particular photo can now be found on websites across the net, has been featured in the Honolulu Daily Star, West Hawai’i Today and other local papers. It has also been used for numerous professional presentations by Keck affiliated astronomers and staff.
I understand that this month it is in Hana Hou! the inflight magazine for Hawaiian Airlines. (Somebody get me a copy. Please! I am not flying anywhere in the next month.) Not the first magazine appearance, you can also find the shot in an issue of Astronomy magazine.
It can be a lot of fun seeing an image I created become something of an iconic image of the observatory.