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Aperture Photometry

The DAOPHOT aperture photometry of the M92 fields was carried out using an 8 diameter aperture and 5 wide sky annulus for each source. This is a relatively large aperture and is thus influenced by more noise in the background sky than is desirable. If the image quality is good enough, better signal-to-noise measurements can be obtained using a smaller aperture and an aperture correction term that corrects to an effectively infinite sized aperture. This correction factor is traditionally measured from the photometric curve-of-growth taken from images of relatively bright, high-signal-to-noise points stars in uncrowded regions. The use of small apertures plus correction terms also makes it possible to use aperture photometry in more crowded regions.

Gaylin Laughlin
Wed Feb 22 09:42:23 PST 1995