I’m spending a week in Connecticut visiting my parents. We are expecting hurricane Irene to come barreling through over the weekend, mostly on Sunday, but in the meantime, the weather has been quite pleasant. After a 22 mile bike ride this morning through the woods, followed by a trip to Foxwoods Casino in the afternoon, I spent an hour or two this evening standing outside in the dark trying to capture the night sky. Busy day.
Around here, which some might consider “deep in the woods”, there is not much ground light, and plenty of stars as a result. I decided to use tree silhouettes as an anchor point, to give the images some frame of reference. Trees are abundant here, and this also then serves as my entry into this week’s DPS Assignment, conveniently themed “Trees”.
With camera mounted securely to my tripod, and using a remote shutter release, I tried a variety of camera settings, including long exposures and high ISOs. With the high ISO, you of course get higher sensitivity (requiring less light to make the image), but more noise. On the other hand, keeping the shutter open longer means more total light hitting the sensor, allowing for lower ISO, but also results in star smudging as the stars move through the image due to the Earth’s rotation. Even with a 30 second exposure, the movement is quite noticeable.
So in some cases, I tried to keep the smudging to a minimum with exposures as “fast” as 8 to 10 seconds. In others, I went the opposite direction and let the streaking be part of the image, using a 4 minute in one case and an 8 minute exposure in another. For these ultra long exposures, I put the camera in “bulb” mode and made use of the remote shutter release which offers a means to lock the shutter open. I used a timer to decide when to end the exposure, but getting the time exact is not too critical. At 8 minutes, a couple seconds one way or the other is not going to make much difference.
In these cases, I am also using a fairly wide aperture (big opening means lots of light), but that is not the greatest for keeping both the tree and the stars in perfect focus. Still, it helps keep the other parameters at reasonable levels, and with a 35mm lens, the effect is not too bad. Would be even better at 14mm (as would the view of the sky), but unfortunately I did not bring my wide angle lens on this trip.
I do like how the clouds show up with a bit of a reddish tinge. They do not appear that way in real life, at least to my eyes. I presume the tint has to do with the sunlight reddened by the long trip sideways through the atmosphere, as during sunset. In this case, the light is coming from beyond the horizon, but the tint has not changed. Still, at night, the light is so minimal that the clouds are themselves barely even visible to the naked eye, but show up nicely in the long exposed image.