SolarTime
gives the angle on the celestial equator between the Sun and the local antimeridian for the current location and date.
SolarTime[loc]
gives the solar time angle for the specified location and current date.
SolarTime[date]
gives the solar time angle for the specified date and current location.
SolarTime[loc,date]
gives the solar time for the specified location and date.
SolarTime["MeanTime",loc,date]
gives the mean solar time for the specified location and date.
Details
- Solar time is typically used when precise orientation with respect to the Sun is required, for example, in applications of solar energy, solar trackers and heliostats.
- SolarTime gives an angle determined by a sundial from the given location at the given date.
- SolarTime returns a Quantity angle expressed in mixed units of hours, minutes and seconds of right ascension, as traditionally done with angles measured along the celestial equator.
- SolarTime[loc,date], equivalent to SolarTime["ApparentTime",loc,date], computes the local apparent or true solar time, based on the celestial position of the true Sun, which moves at irregular speed along the celestial equator.
- SolarTime["MeanTime",loc,date] computes local mean solar time, based on the position of the fictitious mean Sun, which moves at constant speed along the celestial equator.
- SolarTime[loc,date] is equivalent to the difference between the sidereal time of the antipode of loc at date and the right ascension of the Sun for the same date.
- SolarTime[] makes use of Here and Now to determine your current location and date.
- Locations in SolarTime[loc,date] can be given as {lat,lon} pairs in degrees, GeoPosition objects or Entity geo locations.
- Date specifications in SolarTime[loc,date] can be given as DateObject expressions or date strings. Input dates are assumed to be given in Universal Time, modified by your local time zone as given by $TimeZone.
Examples
open allclose allBasic Examples (2)
Scope (3)
Find the solar time for your current location and date:
Use locations in different formats:
Specify dates as DateObject expressions or date lists:
Applications (3)
The difference between apparent and mean solar times varies during a year:
This is the so-called equation of time, given in minutes:
Find the minimum and maximum of the values of the equation of time:
Construct a function that finds the civil time of solar noon:
Take all civil noons during a year, ignoring daylight saving changes:
Compute the corresponding solar noons for your location:
Find the durations of all solar days during a year:
The duration varies during the year, with longer days in June and December, and shorter days in March and September:
Properties & Relations (6)
For a given location and date, solar time can also be computed from AstroPosition:
Locations with the same longitude have similar solar time:
Each 15 degrees of longitude correspond to about one hour of solar time:
Solar time is not defined at the poles, because longitude is not uniquely defined at the poles:
Mean solar time for Greenwich was the basis for GMT time:
However, it does not coincide in general with true solar time at Greenwich:
This is the current time at that location, with the unique time zone GMT+8 used in China:
It is shifted by more than two hours with respect to the corresponding solar time:
Compute the sidereal time of the antipode of that location, for that date:
Compute the right ascension of the Sun for that location and date:
Then the solar time is equivalent to this difference, modulo full angles:
Text
Wolfram Research (2021), SolarTime, Wolfram Language function, https://reference.wolfram.com/language/ref/SolarTime.html.
CMS
Wolfram Language. 2021. "SolarTime." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/SolarTime.html.
APA
Wolfram Language. (2021). SolarTime. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/SolarTime.html