SiderealTime

SiderealTime[]

gives the right ascension of the local meridian for the current date and location.

SiderealTime[date]

gives the right ascension of the local meridian for the specified date.

SiderealTime[loc]

gives the right ascension of the local meridian for the specified location.

SiderealTime[loc,date]

gives the right ascension of the local meridian for the specified date and location.

SiderealTime[{{loc1,date1},{loc2,date2},}]

gives the right ascensions of the local meridians for all specified locations on the specified dates.

SiderealTime[loc,date,func]

uses func to determine what to return for extended locations.

Details

  • SiderealTime[] makes use of $GeoLocation and $TimeZone to determine your location and time zone.
  • Locations can be specified as Entity objects, assuming they represent objects with geographic coordinates or GeoGraphics primitives, or they can be latitude/longitude pairs, assuming degrees as units.
  • Dates can be specified as a DateObject or as a string that resolves to a date.
  • loc and date can be either individual items or lists of them.
  • If datespec is a list of dates, then the results will contain TimeSeries objects.
  • datespec can be specified as {start,end,increment} for compatibility with DateRange specifications.
  • SiderealTime[,func] is used to specify the format of output when extended locations are specified.
  • Possible settings for func include:
  • Automaticreturns intervals for extended locations only
    Intervalreturns intervals for all specified locations
    Meanreturns mean value for extended locations
    Minreturns minimum values for extended locations
    Maxreturns maximum values for extended locations
    StandardDeviationreturns standard deviation for extended locations

Examples

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Basic Examples  (5)

Compute the sidereal time for your current location:

Compute the sidereal time for a specified date:

Compute the sidereal time for a specified location:

Compute the sidereal time for a specified latitude/longitude and date:

Compute the sidereal time for a specified city and date:

Scope  (8)

Dates  (3)

Dates can be specified as a DateObject:

Dates can be specified as a date string:

Generate the sidereal time for a range of dates:

Locations  (5)

Locations can be latitude/longitude pairs:

Cities are treated as single, specific locations:

Results for extended locations are intervals, by default:

The form of the results for extended locations can be overridden:

Generate the sidereal time for multiple locations:

Applications  (1)

Plot the equation of time by finding the difference between the Sun's right ascension at noon and the sidereal time at noon:

Properties & Relations  (3)

The output of SiderealTime is an angle, not a time:

SiderealTime tracks Earth's rotation with respect to the fixed stars, with a full rotation taking one sidereal day:

Earth rotates with respect to the fixed stars in less than one day, and it needs to rotate a bit more to complete a full (solar) day:

The effect accumulates during one year and hence Earth rotates 366.242 times with respect to the fixed stars in 365.242 days:

Equivalently:

Possible Issues  (1)

Although it looks like a time-based concept, SiderealTime is actually an angle:

Neat Examples  (1)

Choose a location and a date:

This is the sidereal time of that location at that time:

Take the right ascensions of the Sun, the Moon and the planets:

Construct text labels for them:

Plot the directions of the Sun, the Moon and the planets as viewed from the South Pole, with respect to the fixed stars:

Introduced in 2014
 (10.0)