The North polar sequence is a group of 96 stars that was used to define stellar magnitudes and colors. The cluster of stars lies within two degrees of the Northern Celestial pole

Celestial pole

The north and south celestial poles are the two imaginary points in the sky where the Earth's axis of rotation, indefinitely extended, intersects the imaginary rotating sphere of stars called the celestial sphere...

, which makes them visible to everyone on the northern hemisphere

Northern Hemisphere

The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

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Originally proposed by Edward Charles Pickering

Edward Charles Pickering

Edward Charles Pickering was an American astronomer and physicist, brother of William Henry Pickering.Along with Carl Vogel, Pickering discovered the first spectroscopic binary stars. He wrote Elements of Physical Manipulations .Pickering attended Boston Latin School, and received his B.S. from...

, the system was used between 1900 and 1950. Today it has been replaced by the UBV photometric system

UBV photometric system

UBV photometric system, also called the Johnson system , is a wide band photometric system for classifying stars according to their colors. It is the first known standardized photoelectric photometric system. The letters U, B, and V stand for ultraviolet, blue, and visual magnitudes, which are...

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External links

• Data at Google books
• Schematic images