Right ascension converter
Convert a star’s right ascension between hours, minutes and seconds and decimal degrees, or back.
That's about the same as the Orion Nebula.
What it means
Where is that on the sky?
Star positions are J2000. Right ascension minutes and seconds are time units, 15 times larger than arcminutes and arcseconds.
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That position in every unit
Learn
Three things worth knowing
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Hours × 15
RA 5h 35m is 5.583 h × 15 = 83.75°. Degrees ÷ 15 gives hours.
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Clocks and stars
Telescopes on a meridian circle timed stars as they crossed the meridian, so a star’s position was recorded as the clock time of its crossing.
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RA seconds are not arcseconds
One second of right ascension is 15 arcseconds (at the equator). Mixing them puts a star 15 times off.
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Background
About right ascension
Right ascension is the sky’s longitude. Because the sky turns once a day, astronomers measure it in time: 24 hours make the full circle, so 1 h = 15°, 1 minute = 15 arcminutes and 1 second = 15 arcseconds.
A star with RA 6h is overhead six hours of sidereal time after one at 0h. The other coordinate, declination, is ordinary degrees north or south.