photographic photometry
Quick Summary
Photometry in astronomy is the measurement of the brightness of celestial objects. This measurement provides crucial information about an object's structure, temperature, and distance. Historically, stars were classified into magnitudes, with the brightest being first magnitude and the faintest visible to the naked eye being sixth magnitude. This system was refined to use a constant ratio for brightness steps, where a five-magnitude difference equals a 100:1 ratio in light intensity.1
The advent of photography introduced a more objective method for measuring star brightness. However, photographic plates are sensitive to different wavelengths than the human eye, leading to distinct visual and photographic magnitude scales. The difference between these scales, known as the color index, indicates a star's surface temperature. Modern photometry utilizes more sensitive photoelectric detectors and CCDs, allowing for precise measurements across a wider range of the electromagnetic spectrum. These advanced techniques enable detailed analysis of stars, including their classification and the effects of interstellar dust.123
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