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More About Parallax

Astronomers can measure parallax by measuring the position of a nearby star very carefully with respect to more distant stars behind it, then measuring those distances again six months later when the Earth is on the opposite side of its orbit. The shift is tiny... less than an arcsecond even for the nearest star (an arcsecond is 1/60 of an arcminute, which is 1/60 of a degree).

Info Tell me more about finding distances to stars

parallax diagram

The formula for finding the distance to a star, measured in parsecs, using the star's parallax, measured in arcseconds, is:

parallax formula

Info Tell me how to derive the parallax formula.

Return Click here to return to finding the distance to HT Cas using parallax.

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This page last updated: Monday, 30-Jan-2006 12:11:59 EST