Photoelectric Photometry Newsletter

Photoelectric Photometry Programs: General Considerations

• Photoelectric photometry - by amateurs or professionals - can contribute signific- antly to astronomical research. Make sure your program is scientifically worthwhile. Amateurs can make an especially valuable contribution by making systematic observations over a long period of time: months and years.
• Photoelectric photometry should be enjoyable as well as satisfying. Don't forget what the word "amateur" means.
• Consult with the AAVSO, the IAPPP or your local professional astronomer for advice in choosing a program and carrying it out.
• There are definite advantages to working with a group, on an established program or campaign. You get more feedback that way.
• Choose a program which fits your equipment, site, ability and time available. Even if your site is mediocre, a few well-chosen observations in a night are quite worthwhile. Choose stars with relatively long periods.
• It may be difficult for the program coordinator to combine observations of one star by very many observers, especially if they have not all been careful in correcting and transforming their observations. Consider "adopting" a few stars and observing them regularly.
• Don't over-extend yourself. Bite off something you can chew. Strive for the greatest accuracy you can attain, by making your observations carefully and correcting carefully for extinction, gain settings and color effects. Don't observe on cloudy nights. A dubious observation is worse than no observation at all.
• Computer acquisition and reduction of data is acceptable, but is no substitute for careful observation.
• If your sky is non-uniform or otherwise imperfect, concentrate on differential photometry, with comparison stars close to the variable.
• If your telescope is small, your photometer insensitive or your sky bright, stick to bright stars. There are over 1000 stars in the Bright Star Catalogue which require photometry.
• Don't observe variables and comparison stars of different colors unless you are sure of your transformation coefficient. Don't observe variables and comparison stars on different gain settings unless you are sure of your gain setting calibrations.
• If you are really confident of your equipment, your sky and your data reduction procedures, you might want to try absolute photometry. Many of the comparison stars on the various AAVSO charts are in need of accurate magnitudes and colors. For many purposes, it is adequate to observe in one filter only: usually V. Follow standard procedures for reducing data: correcting for extinction, color effects and gain settings.
• You will get more satisfaction from your observations if you see them published or made available to the astronomical community. Make sure that this is being done
• Observe at least two comparison stars, and calculate and publish delta m(Cl-C2).
• Keep detailed, adequate records.

John R. Percy Department of Astronomy Toronto, Canada M5S lA7