Several computer programs that will perform photometric measurements are available to amateur astronomers. Essentially, you load an image from your CCD, designate the variable star, as well at the comparison star and a check star. The computer program will then compare the brightness of each star. When finished, the program will provide a report indicating the difference in magnitude between each star. Programs such as this are absolutely required when using a CCD. When using a photometer, a spreadsheet can be developed to quantify your measurements.
Both of these methods are beyond the scope of this book but there are several books available to assist you should you begin CCD or PEP observations. A few that I would recommend are The Handbook of Astronomical Image Processing, by Richard Berry and James Burnell; Photoelectric Photometry of Variable Stars, by Douglas Hall and Russell Genet; and Astronomical Photometry by Arne Henden and Ronald Kaitchuck, all published by Willmann-Bell. Also, Arne tells me that he has a new CCD photometry book coming out after this one, so keep an eye open for it.
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