Astrophysics (Index)About

north polar sequence

(set of stars previously used to define magnitudes)

The north polar sequence (NPS) is a set of stars that were used to calibrate magnitudes before the adoption of the UBV photometric system. The stars were all close to the celestial north pole (within about two degrees), making them observable any (clear) night from northern hemisphere sites, convenient for calibration of other observations. It numbered roughly a hundred stars at its largest, having been expanded over time.

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