home     galleries     new     equipment     links     about    contact

Night sky, Joshua Tree National Park        Images © Mark A. Chappell

Finding a reasonably clear night sky is a problem in southern California, which is so heavily populated that no matter where you point your camera you're likely to pick up the glow of a town or city on the horizon.   In search of the best night sky within easy reach, a friend and I drove out to Joshua Tree National Park and these images are the result.   The nights were clear with a new moon, so the Milky Way was visible, and it can be seen in most of these photos.   They are, of course, long exposures.   The images with 'fixed' stars were 1-2 min exposures at high ISO (1600-3200) on digital cameras.   The 'star trails' came from 17- 28-min exposure at low ISO (the 'clouds' in the sky result from the rotation of the Milky Way).   I used my headlamp or an electronic flash to 'paint' Joshua trees in the foreground for several of the images.   There was definitely some light pollution on the horizon, but I think it improves some of the pictures (especially the one at upper left, with the Joshua tree on the horizon enveloped in the arched branch of a nearer tree).   What looks like a reflecting lake in the lower right image is the roof of my friend's car, upon which I propped the camera for this shot.           Night sky imagery pushes the limits of current digital SLRs: you need high ISO to 'freeze' the stars (exposures must be a minute or less, even with wideangle lenses), but that generates considerable sensor noise.  Fast ultrawideangle lenses could help, but these are very expensive.   You can use lower ISO for star trails, but again, there is a sensor noise problem resulting from the very long exposures necessary to get good 'trails'.   Battery life is also a problem, especially since a period of 'dark frame subtraction' equal to the exposure duration is needed to reduce sensor noise and yield the best results.  FInally, finding the correct focus is a challenge; autofocus systems are generally useless on a dark night, so it's necessary to switch to manual and prefocus on some distant bright object: the moon (if visible), a sign, anything far away.           For star trails, film in an all-mechanical camera may be a better way to go, although instead of sensor noise, one must content with reciprocity failure and color shifts.

Canon 1D Mk. II, 1D3, 30D, Canon 17-40 lens at 17 mm or Sigma 12-24 lens at 12 mm (2007, 2008)