If I'd like to watch star like Betelgeuse that has coordinates - right ascension 05h 55m 10.30536s and declination +07° 24′ 25.4304″.

  • If my local sidereal time is 05h 55m 10.30536s does it mean that Betelgeuse crossed my meridian?

  • And if I want to track it with right ascension on the telescope I can define it as LST - RA of a star take this number and put it on the RA axis of a telescope and see a star?

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    $\begingroup$ LST - RA is better known as the "Hour Angle" of an object. It is 0 when the object is on the meridian, and increases for every hour of RA past that time. en.wikipedia.org/wiki/Hour_angle $\endgroup$ Feb 28, 2023 at 14:13

1 Answer 1


If your local sidereal time is 05h 55m 10.30536s, then Betelgeuse is on the meridian. The local sidereal time is always equal to the right ascension of a point on the meridian.


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