A note about the ISO setting on digital cameras as applies to night sky photographs: The higher the ISO setting, the more sensitive the camera is, more and brighter stars. But there is a compromise. The higher the ISO setting, the more noise that is generated and appears in the photo. (Click on the following thumbnails and if you can't see stars in the pictures, your monitor settings are in serious need of adjustment. It only takes a minute to change the settings, and it will improve how you see ALL pictures on your monitor, including your own.)


ISO 400
Lots of stars in this picture. The stars standout pretty good against a dark sky background. ISO 200 would probably be too dark for this picture/camera/exposure combination. Some noise is evident, but not too bad (some of it is compression artifacts too).
Shutter speed: 15.0 sec
Aperture: f/2.8
Zoom (Focal length): 33mm (equiv.)*
Exposure bias: +0.0 EV
Original image size: 640 x 480 Pixels
Flash used: No
Date taken: Saturday, May 03, 2008
Time taken: 9:26 PM
Camera make: Canon
Camera model: Canon PowerShot SX100 IS



ISO 800
A lot more stars in this picture. This is brighter yet, and the background sky is still dark enough to provide good contrast for the stars. More noise is evident, but the picture is still very usable. (some compression artifacts too) The ISO 800 setting was about right for this photo.
Shutter speed: 15.0 sec
Aperture: f/2.8
Zoom (Focal length): 33mm (equiv.)*
Exposure bias: +0.0 EV
Original image size: 640 x 480 Pixels
Flash used: No
Date taken: Saturday, May 03, 2008
Time taken: 9:27 PM
Camera make: Canon
Camera model: Canon PowerShot SX100 IS



ISO 1600
Much brighter, but only because of the noise. You can actually see less stars because the noise has washed them out. To me this photo is unusable. The ISO 1600 setting has pushed the sensitivity over the limit, at least for the combinations of this photo.
Shutter speed: 15.0 sec
Aperture: f/2.8
Zoom (Focal length): 33mm (equiv.)*
Exposure bias: +0.0 EV
Original image size: 640 x 480 Pixels
Flash used: No
Date taken: Saturday, May 03, 2008
Time taken: 9:28 PM
Camera make: Canon
Camera model: Canon PowerShot SX100 IS


My next project: Experimenting with taking pictures through my telescope, binoculars, and whatever else I can get my hands on!