I drove home via Cathedral Rock hoping to see something difference, and it seems I did!!! I saw this Western Rattlesnake (according to my book) about to cross the track I was on, so I slammed on the brakes, grabbed the camera and spent about 20 minutes taking 250 shots!! I was so excited, as it's the first rattlesnake I've seen in almost 4 years in Colorado, that I neglected to check my ISO, which was set to 400 :-(. To be honest I didn't care what the pictures turned out like because the whole experience was so thrilling and satisfying, being able to get so close to something so potentially dangerous and yet it was so calm and a pleasure to be with. It was about three foot long and I counted 11 'segments' on its rattle. If I hadn't wandered so far from my running car (!!) I would have gone back for my macro lens as I was getting closer than my 300mm would focus, and yes, I'm being serious!!! For once this is the full frame as I decided it didn't need cropping. What a rush - I loved every second!