Sunrise from Mt. Shavano

I had lost the previous night’s sleep hiking up Tabeguache Peak in the dark and shooting sunrise from its summit, so I was feeling rather weary when the alarms went off at 11:30 p.m., signaling the beginning of my ascent of Mt. Shavano. By now the trail was familiar, and I summited Shavano in time to photograph a beautiful display of crepuscular rays to the east just before sunrise. Crepuscular rays, also called god beams, form when shafts of sunlight shine through holes in dense clouds. In this case, the clouds forming the rays were out of sight below the eastern horizon. We see the shafts of light only because the dusty air scatters some of the sunlight to our eyes. The long path the sunlight takes through the atmosphere at sunrise causes the blue light to scatter out of the beam. The reddish light that’s left goes straight ahead, causing the shafts of light to take on a reddish hue. The sun is so far away that its rays are essentially parallel. The beams apparently converge at the horizon for the same reason that railroad tracks, which are actually parallel to each other, appear to converge when we stand between the tracks and sight along them.

During my nighttime ascent I had noticed a jewel-like patch of alpine wildflowers just below the summit. Now, as I was descending, I retraced my steps with the help of my GPS receiver and relocated the flowers. I set up and tried to photograph them, but discovered to my annoyance that auto-focus had apparently stopped working. Repeatedly I pressed the shutter release halfway down, (the default technique for starting auto-focus) but the lens wouldn't respond. I checked the auto-focus switch on the lens. It was set to auto. I checked the camera body. Auto-focus was enabled there. I switched lenses, but got the same behavior. Again and again I pressed the shutter release halfway down, hoping the camera wasn’t broken, but still nothing happened. After puzzling over this issue for a good five minutes, I finally remembered that a year and a half earlier I had removed the auto-focus function from the shutter release and assigned it to a button on the rear of the camera. For the past year and a half, I had always focused with the button on the rear of the camera, not the shutter release. Just half an hour earlier I had been pressing that rear-mounted button every time I wanted to focus. Granted, I was at 14,000 feet. The night before last, I had gotten up at 10:30 p.m. so I could summit Tabeguache at 4 a.m. Last night I'd gotten up at 11:30 p.m. so I could summit Mt. Shavano at 4:30 a.m. So I had hypoxia and sleep-deprivation as excuses, but forgetting how to auto-focus? Sheesh!