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API Reference — Units

When you ask positions to return distances, velocities, or angles, they return instances of the following classes.

class skyfield.units.Distance(au=None, km=None, m=None)

A distance, stored internally as au and available in other units.

You can initialize a Distance by providing a single float or a float array as either an au=, km=, or m= parameter.

au

The distance in astronomical units.

km

The distance in kilometers.

m

The distance in meters.

length()

Compute the length when this is an x,y,z vector.

The Euclidean vector length of this vector is returned as a new Distance object.

>>> from skyfield.api import Distance
>>> d = Distance(au=[1, 1, 0])
>>> d.length()
<Distance 1.41421 au>
light_seconds()

Return the length of this vector in light seconds.

to(unit)

Convert this distance to the given AstroPy unit.

class skyfield.units.Velocity(au_per_d=None, km_per_s=None)

A velocity, stored internally as au/day and available in other units.

You can initialize a Velocity by providing a float or float array to its au_per_d= parameter.

au_per_d

The velocity in astronomical units per day.

km_per_s

The velocity in kilometers per second.

to(unit)

Convert this velocity to the given AstroPy unit.

class skyfield.units.Angle(angle=None, radians=None, degrees=None, hours=None, preference=None, signed=False)
degrees

The angle in degrees (360° in a circle).

hours

The angle in hours (24 hours in a circle).

radians

The angle in radians (𝜏 = 2𝜋 in a circle)

arcminutes()

Return the angle in arcminutes.

arcseconds()

Return the angle in arcseconds.

mas()

Return the angle in milliarcseconds.

hms(warn=True)

Convert to a tuple (hours, minutes, seconds).

All three quantities will have the same sign as the angle itself.

signed_hms(warn=True)

Convert to a tuple (sign, hours, minutes, seconds).

The sign will be either +1 or -1, and the other quantities will all be positive.

hstr(places=2, warn=True)

Convert to a string like 12h 07m 30.00s.

dms(warn=True)

Convert to a tuple (degrees, minutes, seconds).

All three quantities will have the same sign as the angle itself.

signed_dms(warn=True)

Convert to a tuple (sign, degrees, minutes, seconds).

The sign will be either +1 or -1, and the other quantities will all be positive.

dstr(places=1, warn=True)

Convert to a string like 181deg 52' 30.0".

to(unit)

Convert this angle to the given AstroPy unit.