Calendars and time
Local Sidereal Time
Direct answer
Local Sidereal Time is sidereal time adjusted for an observer's longitude, indicating the right ascension on the local meridian.
Local Sidereal Time tells which right ascension is crossing a site's meridian.
$0 today, then $12/month after 7 days. Cancel anytime.
At a glance
- Found in
- Calendars & Timekeeping
- Related
- Greenwich Sidereal Time, Dynamical Time, Calendar, Julian Date
Local Sidereal Time tells which right ascension is crossing a site's meridian.
A cycle or timeline schematic for comparing the named timekeeping concept.
What does your own chart say about you?
Choose love, work or purpose. Your reading is written from your chart. Your reading uses your own birth details.
Walk through Alex’s whole example first
The Road of AgesSee the turning points of your whole life, from your birth date
See your road's shape
Prefer to explore first?
The Road of AgesThe turning points of your whole life, from your own chart
Walk my road
Free, by email
Your daily Almanac letter
One short letter at 7 each morning: the day’s theme read for your own chart, and one thing to do with it.
The story behind Local Sidereal Time
Local sidereal clocks were standard observatory instruments before computerized mount control.
Why Local Sidereal Time matters
Local Sidereal Time connects a celestial catalog to the sky currently overhead at a particular observing location.
How to read Local Sidereal Time
Local Sidereal Time for telescope alignment, hour-angle calculation, and planning applies when an object culminates.
Local Sidereal Time in practice: an example
An object culminates near the moment its right ascension equals the observer Local Sidereal Time.
Sources and editorial method
Research references used for this entry include:
- U.S. Naval Observatory Circular 179: The IAU Resolutions on Astronomical Reference Systems, Time Scales, and Earth Rotation Models - Technical reference for TAI, TT, TCG, TCB, TDB, UT1, sidereal time, epochs, and Earth rotation.
- IAU SOFA: Time Scale and Calendar Tools - IAU-standard algorithms and guidance for civil calendars, Julian dates, and seven recognized astronomical time scales.
- Source
- The Great Almanac Dictionary
- Category
- Calendars & Timekeeping
- Last updated
- 2026-09-26
Calculate what crosses your meridian
A definition tells you what it is; your own birth chart tells you what it means for you. The Oracle casts your real chart and answers for your love, your work, and your year ahead, in conversation. It opens with the 7-day Seeker trial.
Speak with the OracleRelated terms
More in Calendars & Timekeeping
- Proleptic Gregorian Calendar
- Solar Calendar
- UT1
- Astronomical Year Numbering
- Civil Day
- DUT1
- GPS Time
- ISO Week Date
From the reference page to your own chart
Every word here
is in your own chart.
- A personal reading about love, work or purpose, written from your chart
- A practical next step to consider
- It opens with 7 days free, with the AI Oracle and daily guidance
$0 today, then $12/month after 7 days. Cancel anytime.
Common questions
What is local sidereal time?
Local Sidereal Time is sidereal time adjusted for an observer's longitude, indicating the right ascension on the local meridian.
Why does local sidereal time matter?
Local Sidereal Time connects a celestial catalog to the sky currently overhead at a particular observing location.
Free, by email
The Almanac, in your inbox at 7
One short letter at 7 each morning: the day’s theme read for your own chart, and one thing to do with it.
