When reading the article in the April 2011 Sky & Telescope by Brian Kloppenburg and Tom Pearson about photometry with digital cameras, I was reminded of an article I wrote 5 years ago entitled "Measuring Skyglow with Digital Cameras." (Click here to download the article in PDF form.)
The article is (to my admitedly biased taste) full of good ideas that aren't fully fleshed out. I was hoping that someone would take those ideas and run with them — bring them into a form that's usable by the average amateur. It hasn't happened, so I'm issuing the challenge again.In retrospect, I spent far too much time talking about point-and-shoot cameras and too little on digital SLRs, which are more suitable for this application. At the time, many point-and-shoot cameras still had the manual controls and sensitivity needed for scientific work, while DSLRs were the province of professional photographers and a few serious amateurs. These days, point-and-shoot cameras have become more automatic and les sensitive, and DSLRs have become cheap enough for many people to buy.
Why use DSLRs to measure skyglow when the Sky Quality Meter is so convenient and relatively cheap? Because the SQM measures only the zenith and can't cope with the horizon, where light pollution is at its worst — and most directional. The SQM would probably yield a number around magnitude 19.5 per square arcsecond for the sky at my astronomy club's observing field, hiding the fact that it's overwhelmingly bright to the southeast, in the direction of Boston, and almost tolerable to the northwest, as shown in my digital camera mosaic.
What more needs to be done? A lot! My mosaics are produced with lots of manual labor that could theoretically be made automatic — calibrating the measurement, determining the precise fields of the component frames by matching star fields, and stitching the mosaic together. Software exists to solve each one of these problems separately, but not all together. It's all a matter of computer-programming time — which I don't have. Any takers?