Last light over Green Bank

Green Bank, West Virginia has no towering waterfalls nor astounding  geologic formations. Its vistas are upwards through the atmosphere.  Located in the heart of the US National Radio Quiet Zone, its main  attraction is the National Radio Astronomy Observatory, which aims its  radio telescopes towards the very clear radio skies. The view at optical  wavelengths is impressive too, though a far cry from the exotic  pulsars, molecular clouds, and active galactic nuclei that dominate the  radio sky.

After flying into the regional Charlottesville Airport  and driving two and a half hours to the the observatory campus, I spent  several days working on radio astronomy instrumentation in the shadow of  the Green Bank Telescope and the Little Mountain ridge. In addition to  the obvious modern radio emitters, like Wi-Fi and cell phones, which the  surrounding towns must live without, the observatory bans  gasoline-powered cars on the site due to the strong, broadband radio  noise generated by spark ignitions. Reaching our experiment site  requires a diesel car.

The fortuitous conditions which made the  above photo possible occurred on my second night. Most of my  instrumentation work and nearly all analysis work is done from MIT. As I  make only a few site expeditions each year, I always feel I have to  make the most of them, and I usually try to return to work after a quick  dinner. The fantastic Starlight Cafe in the Science Center closed at  six, forcing me to have an early dinner, after which I returned to the  site. I worked quickly, tidying up wiring and disassembling an antenna,  trying to finish my outdoor work before dark. Slightly after seven, I  walked back to the lab in search of a pair of pliers, and returned after  twenty minutes of searching in the basement. Heading back outside, I  glanced through the window, upset that it appeared nearly dark.

Outside,  though, some light remained. The sunset was blocked by Little Mountain,  a large ridge that towers over the observatory, and so was apparent by  the slow dimming of the sky. As I returned to the antenna assembly to  finish my work, I noticed the silhouette of the ridge in the sunset. As  the sky dimmed, the ridge became darker and darker, outlined by a  shrinking patch of light sky containing the crescent moon. Above that  patch, Jupiter, Orion, Betelguese, Rigel, and Sirius shone brightly  through the clear twilight. I pulled my camera out of my bag, only to  realize that I’d left my tripod in my room in the residence hall. To  retrieve it would take at least twenty minutes, by which time the scene  would be gone. Hoping to do some photography near Green Bank, I'd taken  care to bring along my portable tripod avoid exactly this situation. Oh well. I’m sure it was having fun in my room.

Wanting  to stabilize my camera, but also elevate it to place the ridge near the  bottom of the frame, I climbed on top of the observatory Jeep and  propped up the camera lens on the roof rack. The scene was already too  dark for auto focus and exposure control, so I focused to infinity, set  the shutter to open for five seconds, activated the exposure timer (to  avoid shaking the camera whole pressing the shutter button), and tried  to lie as still as possible on the roof. The photo was a bit dark, so I  took a few longer exposures. Looking at the photos later, I liked the 10  second exposure at 8:42pm best. Indeed the unexpected can be very  rewarding.

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