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Libration functions now calculate apparent angular diameter of the Moon.

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All 4 languages have added a `diam_deg` field to the
structure returned by the Libration function.
It is the apparent angular diameter of the Moon as
seen from the center of the Earth, expressed in degrees.
This commit is contained in:
Don Cross
2021-11-05 16:02:14 -04:00
parent eab9c275b9
commit 296f23af76
29 changed files with 7340 additions and 7165 deletions
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6
source/python/README.md
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@@ -476,6 +476,7 @@ for a given moment in time. See [`Libration`](#Libration) for more details.
| `float` | `mlat` | Moon's geocentric ecliptic latitude. |
| `float` | `mlon` | Moon's geocentric ecliptic longitude. |
| `float` | `dist_km` | Distance between the centers of the Earth and Moon in kilometers. |
| `float` | `diam_deg` | The apparent angular diameter of the Moon as seen from the center of the Earth. |
---
@@ -1516,8 +1517,9 @@ This function calculates a pair of perpendicular libration angles,
one representing rotation of the Moon in eclitpic longitude `elon`, the other
in ecliptic latitude `elat`, both relative to the Moon's mean Earth-facing position.
This function also returns the geocentric position of the Moon
expressed in ecliptic longitude `mlon`, ecliptic latitude `mlat`, and
distance `dist_km` between the centers of the Earth and Moon expressed in kilometers.
expressed in ecliptic longitude `mlon`, ecliptic latitude `mlat`, the
distance `dist_km` between the centers of the Earth and Moon expressed in kilometers,
and the apparent angular diameter of the Moon `diam_deg`.
| Type | Parameter | Description |
| --- | --- | --- |

13
source/python/astronomy.py
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@@ -8554,13 +8554,16 @@ class LibrationInfo:
Moon's geocentric ecliptic longitude.
dist_km : float
Distance between the centers of the Earth and Moon in kilometers.
diam_deg : float
The apparent angular diameter of the Moon as seen from the center of the Earth.
"""
def __init__(self, elat, elon, mlat, mlon, dist_km):
def __init__(self, elat, elon, mlat, mlon, dist_km, diam_deg):
self.elat = elat
self.elon = elon
self.mlat = mlat
self.mlon = mlon
self.dist_km = dist_km
self.diam_deg = diam_deg
def Libration(time):
@@ -8576,8 +8579,9 @@ def Libration(time):
in ecliptic latitude `elat`, both relative to the Moon's mean Earth-facing position.
This function also returns the geocentric position of the Moon
expressed in ecliptic longitude `mlon`, ecliptic latitude `mlat`, and
distance `dist_km` between the centers of the Earth and Moon expressed in kilometers.
expressed in ecliptic longitude `mlon`, ecliptic latitude `mlat`, the
distance `dist_km` between the centers of the Earth and Moon expressed in kilometers,
and the apparent angular diameter of the Moon `diam_deg`.
Parameters
----------
@@ -8596,6 +8600,7 @@ def Libration(time):
mlon = moon.geo_eclip_lon
mlat = moon.geo_eclip_lat
dist_km = moon.distance_au * KM_PER_AU
diam_deg = 2.0 * math.degrees(math.atan(_MOON_MEAN_RADIUS_KM / math.sqrt(dist_km*dist_km - _MOON_MEAN_RADIUS_KM*_MOON_MEAN_RADIUS_KM)))
# Inclination angle
I = math.radians(1.54242)
@@ -8682,4 +8687,4 @@ def Libration(time):
ldash2 = -tau + (rho*math.cos(a) + sigma*math.sin(a))*math.tan(bdash)
bdash = math.degrees(bdash)
bdash2 = sigma*math.cos(a) - rho*math.sin(a)
return LibrationInfo(bdash + bdash2, ldash + ldash2, mlat, mlon, dist_km)
return LibrationInfo(bdash + bdash2, ldash + ldash2, mlat, mlon, dist_km, diam_deg)