Picture of the week

Transit of Mercury

The transit of Mercury across the sun.  This is a partial capture due to being on the west coast as taken between 7:00 and 10:00 AM. 

It is a composite from multiple images captured at 10 minute intervals using a Canon EOS 90D, EF 500mm L f/4 lens, and a solar filter I have hand made and adapted for mounting to this lens.  An intervalometer was used to automate the triggering of the shutter. To track the sun, I manually adjusted the aim of the camera on a regular basis, keeping it in the rough center of the frame.  I then imported the multiple images into Photoshop CS6 as separate layers, manually aligned each, used a blend mode of darken to combine them, along with a manual mask around the perimeter of the sun to tweak some errors caused by atmospheric distortions on the edge.  I found the best settings to have the camera in manual focus, with a manual mode of ISO 400, 1/500th sec, and f/8.  Because I am manually pivoting the camera to track the path of the sun through the sky and without any rotation of the camera, the path of mercury reflects the same arc that the sun has traveled through the sky from my viewpoint.