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All blog post images copyright by Edwardson Tan unless otherwise noted

Thursday, October 18, 2012

Orion and the Pleiades

Last night was probably the clearest in many week. Be that as it may there was still a veil of perceptible haze, and soon after taking the shots I could actually see puffs of clouds beginning to roll in.

I set the Canon T3i to manual mode and dialed in ISO 800. EF-S 18-55mm was zoomed out to 18mm with aperture set to f/5.6. According to photozone at 18mm this lens is sharpest when stopped down to this value. Boo-boo: In those images where I zoomed in to 55mm I forgot to stop down to f/8 (it's sharpest at that setting), but given how I was already getting star trails at 10 sec, it's just as well that I had left the aperture wide open. Image stabilization was turned off and focus switch set to MF.

From experience I knew that a 30-second exposure would begin leaving a conspicuous star trail, so I started with a 20-second exposure. After a couple of shots I increased ISO to 1600 and decreased the shutter speed to 10 sec and later to 8.

Took less than a dozen images and I ended up choosing those shot at ISO 1600 rather than 800.

The omnipresent light pollution from streetlights et al. is annoying and detracts from the images. Fortunately, Orion was close to the zenith and the Pleiades was practically right above me. This reduced the influence of the city lights. To try and get rid of the light spill that was inevitably captured in the images I bumped up the contrast and pulled down the shadows to darken as much as I could without severely affecting the points of light. 

10", f/5.6, ISO 1600, 18mm

8", f/5.6, ISO 1600, 55mm

8", f/5.6, ISO 1600, 55mm

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