Differential photometry - not color index corrected - was attempted as an experiment on Comet 17P on 2007-10-27 9:15 UTC. Using a wide-field camera consisting of a Meade DSI adapted to a fish-eye lens, a wide field (~14 deg) image of the region of Perseus around Comet 17P was taken. The image was dark flatted but not white flatted. Using lam Per as a reference star and AIP4WIN's single star photometry tool, a zero-point was adopted that yielded the Tycho V catalogue magnitude for lam Per. Using lam Per as the reference magnitude, differential photometry was tested on del Per and V 48 Per (MX Per). Estimated magnitudes were within the range of the small variation known for those stars. Differential photometery was then tried on Comet 17P resulting in an estimate of 2.59v+-2%. The comet is probably dimmer than this estimate as color index correction could not be included. There is no internet published color index for the comet. This experiment illustrates how wide-field digital SLRs might be used to prepare a time-series of differential photometry for Comet 17P. Comments and corrections to the above are welcomed and appreciated, as I am doing this as a hobbyist learning exercise. - Kurt Links - Image with data annotations http://gallery.utahastronomy.com/d/10501-2/20071027_17P_Photom.PNG (image with explanation) http://gallery.utahastronomy.com/v/kurt/solarsystem/Comet+17P+Holmes/2007102... Photos about the adapted Meade DSI used to take the image http://gallery.utahastronomy.com/v/kurt/Meade+DSI+Studies/ResolutionTest/?g2... _______________________________________________ Sent via CSolutions - http://www.csolutions.net