Wednesday, August 3, 2016

Cloud Movement Time-lapse

It's been five years since we created a time-lapse of the clouds over Caesar Pond, and today we decided to give it a go again. I am fascinated by the changes that the clouds go through, over time, as illustrated by the clouds in the foreground, versus the clouds in the background, versus the clouds that were at a higher altitude. The clouds build up, break down, and have tendrils that evaporate, etc. The dynamics are incredibly intriguing, and I find that when we look at clouds, we usually just give them a quick glance. We miss the details that the camera picks up over time. (By the dynamics are complex. I found this article on the amount of moisture in clouds to be rather dense with information. The last paragraph, "Cloud Cohesion and Dissolution", of this Wikipedia Cloud Physics article was illuminating as well;-)

We left the camera on for 1 hour and 50 minutes. Drew set the intervalometer to take a photo every 5 seconds as the clouds were moving extremely slowly. This video contains 1,331 jpeg photos. Interestingly, the camera only used 5 out of 16 gigs of the memory card, and the camera battery was at 1 bar when done. If we had done it in RAW, we would have used up our battery rather quickly.

There are several steps to take in setting up the camera. We used the Canon 50d camera with a Canon EF 17-40mm f/4L USM wide angle lens. It was put into AV mode at F13, ISO 100, EV -0.33. First, Drew focused on the clouds across the pond, using auto focus to Infinity, then he switched the camera to Manual Focus to lock the focus in place. The shutter speed varied from 1/400, to 1/500, to 1/640 over the course of the shooting session. (We now think that this variability occurred due to uneven light through the eyepiece. Maybe taping over the eyepiece during the session will alleviate this problem.)

We've got a lot more learning to do before we perfect the process. We also found that our sensor is dirty again, and Drew is going to clean it before we attempt this again. (Note to self: Clean the camera sensor before photographing the sky;-)

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