From 2dd4fc1ab439a30feb9cd813092cf3a31984f9e3 Mon Sep 17 00:00:00 2001
From: Don Cross <cosinekitty@gmail.com>
Date: Wed, 7 Dec 2022 13:03:38 -0500
Subject: [PATCH] Python: rotations for ECT/EQD.

---
 demo/python/astronomy.py             | 57 ++++++++++++++++++++++++
 generate/csdown/csharp_prefix.md     | 28 ++++++------
 generate/hydrogen/c_prefix.md        | 32 +++++++-------
 generate/jsdoc2md/js.hbs             | 28 ++++++------
 generate/kotlindoc/kotlin_prefix.md  |  4 +-
 generate/pydown/py_prefix.md         | 28 ++++++------
 generate/template/astronomy.py       | 57 ++++++++++++++++++++++++
 generate/test.py                     | 33 +++++++++++++-
 source/c/README.md                   | 32 +++++++-------
 source/csharp/README.md              | 28 ++++++------
 source/js/README.md                  | 28 ++++++------
 source/kotlin/README.md              |  4 +-
 source/python/README.md              | 66 ++++++++++++++++++++++------
 source/python/astronomy/astronomy.py | 57 ++++++++++++++++++++++++
 14 files changed, 363 insertions(+), 119 deletions(-)

diff --git a/demo/python/astronomy.py b/demo/python/astronomy.py
index cf41d900..b7a2c593 100644
--- a/demo/python/astronomy.py
+++ b/demo/python/astronomy.py
@@ -7596,6 +7596,63 @@ def Rotation_GAL_EQJ():
         [-0.8676668813529025, -0.1980677870294097, +0.4559861124470794]
     ])
 
+def Rotation_ECT_EQD(time):
+    """Calculates a rotation matrix from true ecliptic of date (ECT) to equator of date (EQD).
+
+    This is one of the family of functions that returns a rotation matrix
+    for converting from one orientation to another.
+    Source: ECT = true ecliptic of date.
+    Target: EQD = equator of date.
+
+    Parameters
+    ----------
+    time : Time
+        The date and time of the ecliptic/equator conversion.
+
+    Returns
+    -------
+    RotationMatrix
+        A rotation matrix that converts ECT to EQD.
+    """
+    et = _e_tilt(time)
+    tobl = math.radians(et.tobl)
+    c = math.cos(tobl)
+    s = math.sin(tobl)
+    return RotationMatrix([
+        [1.0, 0.0, 0.0],
+        [0.0,  +c,  +s],
+        [0.0,  -s,  +c]
+    ])
+
+def Rotation_EQD_ECT(time):
+    """Calculates a rotation matrix from equator of date (EQD) to true ecliptic of date (ECT).
+
+    This is one of the family of functions that returns a rotation matrix
+    for converting from one orientation to another.
+    Source: EQD = equator of date.
+    Target: ECT = true ecliptic of date.
+
+    Parameters
+    ----------
+    time : Time
+        The date and time of the equator/ecliptic conversion.
+
+    Returns
+    -------
+    RotationMatrix
+        A rotation matrix that converts EQD to ECT.
+    """
+    et = _e_tilt(time)
+    tobl = math.radians(et.tobl)
+    c = math.cos(tobl)
+    s = math.sin(tobl)
+    return RotationMatrix([
+        [1.0, 0.0, 0.0],
+        [0.0,  +c,  -s],
+        [0.0,  +s,  +c]
+    ])
+
+
 class ConstellationInfo:
     """Reports the constellation that a given celestial point lies within.
 
diff --git a/generate/csdown/csharp_prefix.md b/generate/csdown/csharp_prefix.md
index def68297..95f37fd4 100644
--- a/generate/csdown/csharp_prefix.md
+++ b/generate/csdown/csharp_prefix.md
@@ -128,10 +128,10 @@ It also allows converting from a vector to spherical (angular) coordinates and b
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
-- **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
+- **EQJ = J2000 Mean Equator**: Uses the Earth's equator on January 1, 2000, at noon UTC.
 - **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
 - **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
-- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
+- **ECL = J2000 Mean Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
@@ -147,22 +147,22 @@ these are used in function and type names.
 | [EquatorFromVector](#Astronomy.EquatorFromVector) | Given an equatorial vector, calculates equatorial angular coordinates. |
 | [VectorFromHorizon](#Astronomy.VectorFromHorizon) | Given apparent angular horizontal coordinates, calculates horizontal vector. |
 | [HorizonFromVector](#Astronomy.HorizonFromVector) | Given a vector in horizontal orientation, calculates horizontal angular coordinates. |
-| [Rotation_EQD_EQJ](#Astronomy.Rotation_EQD_EQJ) | Calculates a rotation matrix from equatorial of date (EQD) to equatorial J2000 (EQJ). |
-| [Rotation_EQD_ECT](#Astronomy.Rotation_EQD_ECT) | Calculates a rotation matrix from equatorial of date (EQD) to true ecliptic of date (ECT). |
-| [Rotation_EQD_ECL](#Astronomy.Rotation_EQD_ECL) | Calculates a rotation matrix from equatorial of date (EQD) to ecliptic J2000 (ECL). |
-| [Rotation_EQD_HOR](#Astronomy.Rotation_EQD_HOR) | Calculates a rotation matrix from equatorial of date (EQD) to horizontal (HOR). |
-| [Rotation_EQJ_EQD](#Astronomy.Rotation_EQJ_EQD) | Calculates a rotation matrix from equatorial J2000 (EQJ) to equatorial of date (EQD). |
-| [Rotation_EQJ_ECL](#Astronomy.Rotation_EQJ_ECL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_HOR](#Astronomy.Rotation_EQJ_HOR) | Calculates a rotation matrix from equatorial J2000 (EQJ) to horizontal (HOR). |
+| [Rotation_EQD_EQJ](#Astronomy.Rotation_EQD_EQJ) | Calculates a rotation matrix from equator of date (EQD) to J2000 mean equator (EQJ). |
+| [Rotation_EQD_ECT](#Astronomy.Rotation_EQD_ECT) | Calculates a rotation matrix from equator of date (EQD) to true ecliptic of date (ECT). |
+| [Rotation_EQD_ECL](#Astronomy.Rotation_EQD_ECL) | Calculates a rotation matrix from equator of date (EQD) to ecliptic J2000 (ECL). |
+| [Rotation_EQD_HOR](#Astronomy.Rotation_EQD_HOR) | Calculates a rotation matrix from equator of date (EQD) to horizontal (HOR). |
+| [Rotation_EQJ_EQD](#Astronomy.Rotation_EQJ_EQD) | Calculates a rotation matrix from J2000 mean equator (EQJ) to equator of date (EQD). |
+| [Rotation_EQJ_ECL](#Astronomy.Rotation_EQJ_ECL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to ecliptic J2000 (ECL). |
+| [Rotation_EQJ_HOR](#Astronomy.Rotation_EQJ_HOR) | Calculates a rotation matrix from J2000 mean equator (EQJ) to horizontal (HOR). |
 | [Rotation_ECT_EQD](#Astronomy.Rotation_ECT_EQD) | Calculates a rotation matrix from true ecliptic of date (ECT) to equator of date (EQD). |
-| [Rotation_ECL_EQD](#Astronomy.Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial of date (EQD). |
-| [Rotation_ECL_EQJ](#Astronomy.Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial J2000 (EQJ). |
+| [Rotation_ECL_EQD](#Astronomy.Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equator of date (EQD). |
+| [Rotation_ECL_EQJ](#Astronomy.Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to J2000 mean equator (EQJ). |
 | [Rotation_ECL_HOR](#Astronomy.Rotation_ECL_HOR) | Calculates a rotation matrix from ecliptic J2000 (ECL) to horizontal (HOR). |
-| [Rotation_HOR_EQD](#Astronomy.Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equatorial of date (EQD). |
+| [Rotation_HOR_EQD](#Astronomy.Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equator of date (EQD). |
 | [Rotation_HOR_EQJ](#Astronomy.Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 equatorial (EQJ). |
 | [Rotation_HOR_ECL](#Astronomy.Rotation_HOR_ECL) | Calculates a rotation matrix from horizontal (HOR) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_GAL](#Astronomy.Rotation_EQJ_GAL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to galactic (GAL). |
-| [Rotation_GAL_EQJ](#Astronomy.Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to equatorial J2000 (EQJ). |
+| [Rotation_EQJ_GAL](#Astronomy.Rotation_EQJ_GAL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to galactic (GAL). |
+| [Rotation_GAL_EQJ](#Astronomy.Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to J2000 mean equator (EQJ). |
 
 ### Gravitational simulation of small bodies
 
diff --git a/generate/hydrogen/c_prefix.md b/generate/hydrogen/c_prefix.md
index d4a82fa5..51dd9a0b 100644
--- a/generate/hydrogen/c_prefix.md
+++ b/generate/hydrogen/c_prefix.md
@@ -54,7 +54,7 @@ To get started quickly, here are some [examples](../../demo/c/).
 | [HelioVector](#Astronomy_HelioVector) | Calculates body position vector with respect to the center of the Sun. |
 | [GeoVector](#Astronomy_GeoVector)     | Calculates body position vector with respect to the center of the Earth. |
 | [Equator](#Astronomy_Equator)         | Calculates right ascension and declination. |
-| [Ecliptic](#Astronomy_Ecliptic)       | Converts J2000 equatorial coordinates to J2000 ecliptic coordinates. |
+| [Ecliptic](#Astronomy_Ecliptic)       | Converts J2000 mean equator coordinates to J2000 ecliptic coordinates. |
 | [EclipticLongitude](#Astronomy_EclipticLongitude) | Calculates ecliptic longitude of a body in the J2000 system. |
 | [Horizon](#Astronomy_Horizon)         | Calculates horizontal coordinates (azimuth, altitude) for a given observer on the Earth. |
 | [PairLongitude](#Astronomy_PairLongitude) | Calculates the difference in apparent ecliptic longitude between two bodies, as seen from the Earth. |
@@ -144,10 +144,10 @@ It also allows converting from a vector to spherical (angular) coordinates and b
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
-- **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
+- **EQJ = J2000 Mean Equator**: Uses the Earth's equator on January 1, 2000, at noon UTC.
 - **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
 - **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
-- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
+- **ECL = J2000 Mean Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
@@ -163,22 +163,22 @@ these are used in function and type names.
 | [EquatorFromVector](#Astronomy_EquatorFromVector) | Given an equatorial vector, calculates equatorial angular coordinates. |
 | [VectorFromHorizon](#Astronomy_VectorFromHorizon) | Given apparent angular horizontal coordinates, calculates horizontal vector. |
 | [HorizonFromVector](#Astronomy_HorizonFromVector) | Given a vector in horizontal orientation, calculates horizontal angular coordinates. |
-| [Rotation_EQD_EQJ](#Astronomy_Rotation_EQD_EQJ) | Calculates a rotation matrix from equatorial of date (EQD) to equatorial J2000 (EQJ). |
-| [Rotation_EQD_ECT](#Astronomy_Rotation_EQD_ECT) | Calculates a rotation matrix from equatorial of date (EQD) to true ecliptic of date (ECT). |
-| [Rotation_EQD_ECL](#Astronomy_Rotation_EQD_ECL) | Calculates a rotation matrix from equatorial of date (EQD) to ecliptic J2000 (ECL). |
-| [Rotation_EQD_HOR](#Astronomy_Rotation_EQD_HOR) | Calculates a rotation matrix from equatorial of date (EQD) to horizontal (HOR). |
-| [Rotation_EQJ_EQD](#Astronomy_Rotation_EQJ_EQD) | Calculates a rotation matrix from equatorial J2000 (EQJ) to equatorial of date (EQD). |
-| [Rotation_EQJ_ECL](#Astronomy_Rotation_EQJ_ECL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_HOR](#Astronomy_Rotation_EQJ_HOR) | Calculates a rotation matrix from equatorial J2000 (EQJ) to horizontal (HOR). |
+| [Rotation_EQD_EQJ](#Astronomy_Rotation_EQD_EQJ) | Calculates a rotation matrix from equator of date (EQD) to J2000 mean equator (EQJ). |
+| [Rotation_EQD_ECT](#Astronomy_Rotation_EQD_ECT) | Calculates a rotation matrix from equator of date (EQD) to true ecliptic of date (ECT). |
+| [Rotation_EQD_ECL](#Astronomy_Rotation_EQD_ECL) | Calculates a rotation matrix from equator of date (EQD) to ecliptic J2000 (ECL). |
+| [Rotation_EQD_HOR](#Astronomy_Rotation_EQD_HOR) | Calculates a rotation matrix from equator of date (EQD) to horizontal (HOR). |
+| [Rotation_EQJ_EQD](#Astronomy_Rotation_EQJ_EQD) | Calculates a rotation matrix from J2000 mean equator (EQJ) to equator of date (EQD). |
+| [Rotation_EQJ_ECL](#Astronomy_Rotation_EQJ_ECL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to ecliptic J2000 (ECL). |
+| [Rotation_EQJ_HOR](#Astronomy_Rotation_EQJ_HOR) | Calculates a rotation matrix from J2000 mean equator (EQJ) to horizontal (HOR). |
 | [Rotation_ECT_EQD](#Astronomy_Rotation_ECT_EQD) | Calculates a rotation matrix from true ecliptic of date (ECT) to equator of date (EQD). |
-| [Rotation_ECL_EQD](#Astronomy_Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial of date (EQD). |
-| [Rotation_ECL_EQJ](#Astronomy_Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial J2000 (EQJ). |
+| [Rotation_ECL_EQD](#Astronomy_Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equator of date (EQD). |
+| [Rotation_ECL_EQJ](#Astronomy_Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to J2000 mean equator (EQJ). |
 | [Rotation_ECL_HOR](#Astronomy_Rotation_ECL_HOR) | Calculates a rotation matrix from ecliptic J2000 (ECL) to horizontal (HOR). |
-| [Rotation_HOR_EQD](#Astronomy_Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equatorial of date (EQD). |
-| [Rotation_HOR_EQJ](#Astronomy_Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 equatorial (EQJ). |
+| [Rotation_HOR_EQD](#Astronomy_Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equator of date (EQD). |
+| [Rotation_HOR_EQJ](#Astronomy_Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 mean equator (EQJ). |
 | [Rotation_HOR_ECL](#Astronomy_Rotation_HOR_ECL) | Calculates a rotation matrix from horizontal (HOR) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_GAL](#Astronomy_Rotation_EQJ_GAL) | Calculates a rotation matrix from J2000 equatorial (EQJ) to galactic (GAL). |
-| [Rotation_GAL_EQJ](#Astronomy_Rotation_EQJ_GAL) | Calculates a rotation matrix from galactic (GAL) to J2000 equatorial (EQJ). |
+| [Rotation_EQJ_GAL](#Astronomy_Rotation_EQJ_GAL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to galactic (GAL). |
+| [Rotation_GAL_EQJ](#Astronomy_Rotation_EQJ_GAL) | Calculates a rotation matrix from galactic (GAL) to J2000 mean equator (EQJ). |
 
 ### Gravitational simulation of small bodies
 
diff --git a/generate/jsdoc2md/js.hbs b/generate/jsdoc2md/js.hbs
index 1c59fc45..c5ce8ec2 100644
--- a/generate/jsdoc2md/js.hbs
+++ b/generate/jsdoc2md/js.hbs
@@ -124,10 +124,10 @@ It also allows converting from a vector to spherical (angular) coordinates and b
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
-- **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
+- **EQJ = J2000 Mean Equator**: Uses the Earth's equator on January 1, 2000, at noon UTC.
 - **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
 - **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
-- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
+- **ECL = J2000 Mean Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
@@ -143,20 +143,20 @@ these are used in function and type names.
 | [EquatorFromVector](#EquatorFromVector) | Given an equatorial vector, calculates equatorial angular coordinates. |
 | [VectorFromHorizon](#VectorFromHorizon) | Given apparent angular horizontal coordinates, calculates horizontal vector. |
 | [HorizonFromVector](#HorizonFromVector) | Given a vector in horizontal orientation, calculates horizontal angular coordinates. |
-| [Rotation_EQD_EQJ](#Rotation_EQD_EQJ) | Calculates a rotation matrix from equatorial of-date (EQD) to equatorial J2000 (EQJ). |
-| [Rotation_EQD_ECL](#Rotation_EQD_ECL) | Calculates a rotation matrix from equatorial of-date (EQD) to ecliptic J2000 (ECL). |
-| [Rotation_EQD_HOR](#Rotation_EQD_HOR) | Calculates a rotation matrix from equatorial of-date (EQD) to horizontal (HOR). |
-| [Rotation_EQJ_EQD](#Rotation_EQJ_EQD) | Calculates a rotation matrix from equatorial J2000 (EQJ) to equatorial of-date (EQD). |
-| [Rotation_EQJ_ECL](#Rotation_EQJ_ECL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_HOR](#Rotation_EQJ_HOR) | Calculates a rotation matrix from equatorial J2000 (EQJ) to horizontal (HOR). |
-| [Rotation_ECL_EQD](#Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial of-date (EQD). |
-| [Rotation_ECL_EQJ](#Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial J2000 (EQJ). |
+| [Rotation_EQD_EQJ](#Rotation_EQD_EQJ) | Calculates a rotation matrix from equator of date (EQD) to J2000 mean equator (EQJ). |
+| [Rotation_EQD_ECL](#Rotation_EQD_ECL) | Calculates a rotation matrix from equator of date (EQD) to ecliptic J2000 (ECL). |
+| [Rotation_EQD_HOR](#Rotation_EQD_HOR) | Calculates a rotation matrix from equator of date (EQD) to horizontal (HOR). |
+| [Rotation_EQJ_EQD](#Rotation_EQJ_EQD) | Calculates a rotation matrix from J2000 mean equator (EQJ) to equator of date (EQD). |
+| [Rotation_EQJ_ECL](#Rotation_EQJ_ECL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to ecliptic J2000 (ECL). |
+| [Rotation_EQJ_HOR](#Rotation_EQJ_HOR) | Calculates a rotation matrix from J2000 mean equator (EQJ) to horizontal (HOR). |
+| [Rotation_ECL_EQD](#Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equator of date (EQD). |
+| [Rotation_ECL_EQJ](#Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to J2000 mean equator (EQJ). |
 | [Rotation_ECL_HOR](#Rotation_ECL_HOR) | Calculates a rotation matrix from ecliptic J2000 (ECL) to horizontal (HOR). |
-| [Rotation_HOR_EQD](#Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equatorial of-date (EQD). |
-| [Rotation_HOR_EQJ](#Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 equatorial (EQJ). |
+| [Rotation_HOR_EQD](#Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equator of date (EQD). |
+| [Rotation_HOR_EQJ](#Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 mean equator (EQJ). |
 | [Rotation_HOR_ECL](#Rotation_HOR_ECL) | Calculates a rotation matrix from horizontal (HOR) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_GAL](#Rotation_EQJ_GAL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to galactic (GAL). |
-| [Rotation_GAL_EQJ](#Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to equatorial J2000 (EQJ). |
+| [Rotation_EQJ_GAL](#Rotation_EQJ_GAL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to galactic (GAL). |
+| [Rotation_GAL_EQJ](#Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to J2000 mean equator (EQJ). |
 
 ### Gravitational simulation of small bodies
 
diff --git a/generate/kotlindoc/kotlin_prefix.md b/generate/kotlindoc/kotlin_prefix.md
index 4ae331fe..40d97e2c 100644
--- a/generate/kotlindoc/kotlin_prefix.md
+++ b/generate/kotlindoc/kotlin_prefix.md
@@ -52,10 +52,10 @@ It also allows converting from a vector to spherical (angular) coordinates and b
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
-- **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
+- **EQJ = J2000 Mean Equator**: Uses the Earth's equator on January 1, 2000, at noon UTC.
 - **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
 - **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
-- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
+- **ECL = J2000 Mean Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
diff --git a/generate/pydown/py_prefix.md b/generate/pydown/py_prefix.md
index fd5c5289..a1c95136 100644
--- a/generate/pydown/py_prefix.md
+++ b/generate/pydown/py_prefix.md
@@ -141,10 +141,10 @@ It also allows converting from a vector to spherical (angular) coordinates and b
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
-- **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
+- **EQJ = J2000 Mean Equator**: Uses the Earth's equator on January 1, 2000, at noon UTC.
 - **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
 - **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
-- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
+- **ECL = J2000 Mean Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
@@ -160,20 +160,22 @@ these are used in function and type names.
 | [EquatorFromVector](#EquatorFromVector) | Given an equatorial vector, calculates equatorial angular coordinates. |
 | [VectorFromHorizon](#VectorFromHorizon) | Given apparent angular horizontal coordinates, calculates horizontal vector. |
 | [HorizonFromVector](#HorizonFromVector) | Given a vector in horizontal orientation, calculates horizontal angular coordinates. |
-| [Rotation_EQD_EQJ](#Rotation_EQD_EQJ) | Calculates a rotation matrix from equatorial of-date (EQD) to equatorial J2000 (EQJ). |
-| [Rotation_EQD_ECL](#Rotation_EQD_ECL) | Calculates a rotation matrix from equatorial of-date (EQD) to ecliptic J2000 (ECL). |
-| [Rotation_EQD_HOR](#Rotation_EQD_HOR) | Calculates a rotation matrix from equatorial of-date (EQD) to horizontal (HOR). |
-| [Rotation_EQJ_EQD](#Rotation_EQJ_EQD) | Calculates a rotation matrix from equatorial J2000 (EQJ) to equatorial of-date (EQD). |
-| [Rotation_EQJ_ECL](#Rotation_EQJ_ECL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_HOR](#Rotation_EQJ_HOR) | Calculates a rotation matrix from equatorial J2000 (EQJ) to horizontal (HOR). |
-| [Rotation_ECL_EQD](#Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial of-date (EQD). |
-| [Rotation_ECL_EQJ](#Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial J2000 (EQJ). |
+| [Rotation_EQD_EQJ](#Rotation_EQD_EQJ) | Calculates a rotation matrix from equator of date (EQD) to J2000 mean equator (EQJ). |
+| [Rotation_EQD_ECT](#Rotation_EQD_ECT) | Calculates a rotation matrix from equator of date (EQD) to true ecliptic of date (ECT). |
+| [Rotation_EQD_ECL](#Rotation_EQD_ECL) | Calculates a rotation matrix from equator of date (EQD) to ecliptic J2000 (ECL). |
+| [Rotation_EQD_HOR](#Rotation_EQD_HOR) | Calculates a rotation matrix from equator of date (EQD) to horizontal (HOR). |
+| [Rotation_EQJ_EQD](#Rotation_EQJ_EQD) | Calculates a rotation matrix from J2000 mean equator (EQJ) to equator of date (EQD). |
+| [Rotation_EQJ_ECL](#Rotation_EQJ_ECL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to ecliptic J2000 (ECL). |
+| [Rotation_EQJ_HOR](#Rotation_EQJ_HOR) | Calculates a rotation matrix from J2000 mean equator (EQJ) to horizontal (HOR). |
+| [Rotation_ECT_EQD](#Rotation_ECT_EQD) | Calculates a rotation matrix from true ecliptic of date (ECT) to equator of date (EQD). |
+| [Rotation_ECL_EQD](#Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equator of date (EQD). |
+| [Rotation_ECL_EQJ](#Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to J2000 mean equator (EQJ). |
 | [Rotation_ECL_HOR](#Rotation_ECL_HOR) | Calculates a rotation matrix from ecliptic J2000 (ECL) to horizontal (HOR). |
-| [Rotation_HOR_EQD](#Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equatorial of-date (EQD). |
+| [Rotation_HOR_EQD](#Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equator of date (EQD). |
 | [Rotation_HOR_EQJ](#Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 equatorial (EQJ). |
 | [Rotation_HOR_ECL](#Rotation_HOR_ECL) | Calculates a rotation matrix from horizontal (HOR) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_GAL](#Rotation_EQJ_GAL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to galactic (GAL). |
-| [Rotation_GAL_EQJ](#Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to equatorial J2000 (EQJ). |
+| [Rotation_EQJ_GAL](#Rotation_EQJ_GAL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to galactic (GAL). |
+| [Rotation_GAL_EQJ](#Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to J2000 mean equator (EQJ). |
 
 ### Gravitational simulation of small bodies
 
diff --git a/generate/template/astronomy.py b/generate/template/astronomy.py
index ff4b7109..b1d1b371 100644
--- a/generate/template/astronomy.py
+++ b/generate/template/astronomy.py
@@ -6090,6 +6090,63 @@ def Rotation_GAL_EQJ():
         [-0.8676668813529025, -0.1980677870294097, +0.4559861124470794]
     ])
 
+def Rotation_ECT_EQD(time):
+    """Calculates a rotation matrix from true ecliptic of date (ECT) to equator of date (EQD).
+
+    This is one of the family of functions that returns a rotation matrix
+    for converting from one orientation to another.
+    Source: ECT = true ecliptic of date.
+    Target: EQD = equator of date.
+
+    Parameters
+    ----------
+    time : Time
+        The date and time of the ecliptic/equator conversion.
+
+    Returns
+    -------
+    RotationMatrix
+        A rotation matrix that converts ECT to EQD.
+    """
+    et = _e_tilt(time)
+    tobl = math.radians(et.tobl)
+    c = math.cos(tobl)
+    s = math.sin(tobl)
+    return RotationMatrix([
+        [1.0, 0.0, 0.0],
+        [0.0,  +c,  +s],
+        [0.0,  -s,  +c]
+    ])
+
+def Rotation_EQD_ECT(time):
+    """Calculates a rotation matrix from equator of date (EQD) to true ecliptic of date (ECT).
+
+    This is one of the family of functions that returns a rotation matrix
+    for converting from one orientation to another.
+    Source: EQD = equator of date.
+    Target: ECT = true ecliptic of date.
+
+    Parameters
+    ----------
+    time : Time
+        The date and time of the equator/ecliptic conversion.
+
+    Returns
+    -------
+    RotationMatrix
+        A rotation matrix that converts EQD to ECT.
+    """
+    et = _e_tilt(time)
+    tobl = math.radians(et.tobl)
+    c = math.cos(tobl)
+    s = math.sin(tobl)
+    return RotationMatrix([
+        [1.0, 0.0, 0.0],
+        [0.0,  +c,  -s],
+        [0.0,  +s,  +c]
+    ])
+
+
 class ConstellationInfo:
     """Reports the constellation that a given celestial point lies within.
 
diff --git a/generate/test.py b/generate/test.py
index fbe6f66c..2cfb2191 100755
--- a/generate/test.py
+++ b/generate/test.py
@@ -1180,6 +1180,11 @@ def Test_RotRoundTrip():
     ecl_hor = astronomy.Rotation_ECL_HOR(time, observer)
     CheckInverse('hor_ecl', 'ecl_hor', hor_ecl, ecl_hor)
 
+    # Round trip #7: EQJ <==> ECT
+    eqd_ect = astronomy.Rotation_EQD_ECT(time)
+    ect_eqd = astronomy.Rotation_ECT_EQD(time)
+    CheckInverse('eqd_ect', 'ect_eqd', eqd_ect, ect_eqd)
+
     # Verify that combining different sequences of rotations result
     # in the expected combination.
     # For example, (EQJ ==> HOR ==> ECL) must be the same matrix as (EQJ ==> ECL).
@@ -1231,7 +1236,32 @@ def Rotation_Pivot():
 
     Debug('PY Rotation_Pivot: PASS')
 
-
+def Test_EQD_ECT():
+    time = astronomy.Time.Make(1900, 1, 1, 0, 0, 0.0)
+    stopTime = astronomy.Time.Make(2100, 1, 1, 0, 0, 0.0)
+    count = 0
+    max_diff = 0.0
+    while time.ut <= stopTime.ut:
+        # Get Moon's geocentric position in EQJ.
+        eqj = astronomy.GeoMoon(time)
+        # Convert EQJ to EQD.
+        eqj_eqd = astronomy.Rotation_EQJ_EQD(time)
+        eqd = astronomy.RotateVector(eqj_eqd, eqj)
+        # Convert EQD to ECT.
+        eqd_ect = astronomy.Rotation_EQD_ECT(time)
+        ect = astronomy.RotateVector(eqd_ect, eqd)
+        # Independently get the Moon's spherical coordinates in ECT.
+        sphere = astronomy.EclipticGeoMoon(time)
+        # Convert spherical coordinates to ECT vector.
+        check_ect = astronomy.VectorFromSphere(sphere, time)
+        # Verify the two ECT vectors are identical, within tolerance.
+        max_diff = max(max_diff, VectorDiff(ect, check_ect))
+        time = time.AddDays(10.0)
+        count += 1
+    if max_diff > 3.743e-18:
+        print('PY Test_EQD_ECT: excessive vector diff = {:0.6e} au.'.format(max_diff))
+        sys.exit(1)
+    Debug('PY Test_EQD_ECT: PASS: count = {}, max_diff = {:0.6e} au.'.format(count, max_diff))
 
 def Rotation():
     Rotation_MatrixInverse()
@@ -1249,6 +1279,7 @@ def Rotation():
     Test_EQD_HOR(astronomy.Body.Mars)
     Test_EQD_HOR(astronomy.Body.Jupiter)
     Test_EQD_HOR(astronomy.Body.Saturn)
+    Test_EQD_ECT()
     Test_RotRoundTrip()
     print('PY Rotation: PASS')
     return 0
diff --git a/source/c/README.md b/source/c/README.md
index fa22f2ac..410c0bf6 100644
--- a/source/c/README.md
+++ b/source/c/README.md
@@ -54,7 +54,7 @@ To get started quickly, here are some [examples](../../demo/c/).
 | [HelioVector](#Astronomy_HelioVector) | Calculates body position vector with respect to the center of the Sun. |
 | [GeoVector](#Astronomy_GeoVector)     | Calculates body position vector with respect to the center of the Earth. |
 | [Equator](#Astronomy_Equator)         | Calculates right ascension and declination. |
-| [Ecliptic](#Astronomy_Ecliptic)       | Converts J2000 equatorial coordinates to J2000 ecliptic coordinates. |
+| [Ecliptic](#Astronomy_Ecliptic)       | Converts J2000 mean equator coordinates to J2000 ecliptic coordinates. |
 | [EclipticLongitude](#Astronomy_EclipticLongitude) | Calculates ecliptic longitude of a body in the J2000 system. |
 | [Horizon](#Astronomy_Horizon)         | Calculates horizontal coordinates (azimuth, altitude) for a given observer on the Earth. |
 | [PairLongitude](#Astronomy_PairLongitude) | Calculates the difference in apparent ecliptic longitude between two bodies, as seen from the Earth. |
@@ -144,10 +144,10 @@ It also allows converting from a vector to spherical (angular) coordinates and b
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
-- **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
+- **EQJ = J2000 Mean Equator**: Uses the Earth's equator on January 1, 2000, at noon UTC.
 - **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
 - **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
-- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
+- **ECL = J2000 Mean Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
@@ -163,22 +163,22 @@ these are used in function and type names.
 | [EquatorFromVector](#Astronomy_EquatorFromVector) | Given an equatorial vector, calculates equatorial angular coordinates. |
 | [VectorFromHorizon](#Astronomy_VectorFromHorizon) | Given apparent angular horizontal coordinates, calculates horizontal vector. |
 | [HorizonFromVector](#Astronomy_HorizonFromVector) | Given a vector in horizontal orientation, calculates horizontal angular coordinates. |
-| [Rotation_EQD_EQJ](#Astronomy_Rotation_EQD_EQJ) | Calculates a rotation matrix from equatorial of date (EQD) to equatorial J2000 (EQJ). |
-| [Rotation_EQD_ECT](#Astronomy_Rotation_EQD_ECT) | Calculates a rotation matrix from equatorial of date (EQD) to true ecliptic of date (ECT). |
-| [Rotation_EQD_ECL](#Astronomy_Rotation_EQD_ECL) | Calculates a rotation matrix from equatorial of date (EQD) to ecliptic J2000 (ECL). |
-| [Rotation_EQD_HOR](#Astronomy_Rotation_EQD_HOR) | Calculates a rotation matrix from equatorial of date (EQD) to horizontal (HOR). |
-| [Rotation_EQJ_EQD](#Astronomy_Rotation_EQJ_EQD) | Calculates a rotation matrix from equatorial J2000 (EQJ) to equatorial of date (EQD). |
-| [Rotation_EQJ_ECL](#Astronomy_Rotation_EQJ_ECL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_HOR](#Astronomy_Rotation_EQJ_HOR) | Calculates a rotation matrix from equatorial J2000 (EQJ) to horizontal (HOR). |
+| [Rotation_EQD_EQJ](#Astronomy_Rotation_EQD_EQJ) | Calculates a rotation matrix from equator of date (EQD) to J2000 mean equator (EQJ). |
+| [Rotation_EQD_ECT](#Astronomy_Rotation_EQD_ECT) | Calculates a rotation matrix from equator of date (EQD) to true ecliptic of date (ECT). |
+| [Rotation_EQD_ECL](#Astronomy_Rotation_EQD_ECL) | Calculates a rotation matrix from equator of date (EQD) to ecliptic J2000 (ECL). |
+| [Rotation_EQD_HOR](#Astronomy_Rotation_EQD_HOR) | Calculates a rotation matrix from equator of date (EQD) to horizontal (HOR). |
+| [Rotation_EQJ_EQD](#Astronomy_Rotation_EQJ_EQD) | Calculates a rotation matrix from J2000 mean equator (EQJ) to equator of date (EQD). |
+| [Rotation_EQJ_ECL](#Astronomy_Rotation_EQJ_ECL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to ecliptic J2000 (ECL). |
+| [Rotation_EQJ_HOR](#Astronomy_Rotation_EQJ_HOR) | Calculates a rotation matrix from J2000 mean equator (EQJ) to horizontal (HOR). |
 | [Rotation_ECT_EQD](#Astronomy_Rotation_ECT_EQD) | Calculates a rotation matrix from true ecliptic of date (ECT) to equator of date (EQD). |
-| [Rotation_ECL_EQD](#Astronomy_Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial of date (EQD). |
-| [Rotation_ECL_EQJ](#Astronomy_Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial J2000 (EQJ). |
+| [Rotation_ECL_EQD](#Astronomy_Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equator of date (EQD). |
+| [Rotation_ECL_EQJ](#Astronomy_Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to J2000 mean equator (EQJ). |
 | [Rotation_ECL_HOR](#Astronomy_Rotation_ECL_HOR) | Calculates a rotation matrix from ecliptic J2000 (ECL) to horizontal (HOR). |
-| [Rotation_HOR_EQD](#Astronomy_Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equatorial of date (EQD). |
-| [Rotation_HOR_EQJ](#Astronomy_Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 equatorial (EQJ). |
+| [Rotation_HOR_EQD](#Astronomy_Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equator of date (EQD). |
+| [Rotation_HOR_EQJ](#Astronomy_Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 mean equator (EQJ). |
 | [Rotation_HOR_ECL](#Astronomy_Rotation_HOR_ECL) | Calculates a rotation matrix from horizontal (HOR) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_GAL](#Astronomy_Rotation_EQJ_GAL) | Calculates a rotation matrix from J2000 equatorial (EQJ) to galactic (GAL). |
-| [Rotation_GAL_EQJ](#Astronomy_Rotation_EQJ_GAL) | Calculates a rotation matrix from galactic (GAL) to J2000 equatorial (EQJ). |
+| [Rotation_EQJ_GAL](#Astronomy_Rotation_EQJ_GAL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to galactic (GAL). |
+| [Rotation_GAL_EQJ](#Astronomy_Rotation_EQJ_GAL) | Calculates a rotation matrix from galactic (GAL) to J2000 mean equator (EQJ). |
 
 ### Gravitational simulation of small bodies
 
diff --git a/source/csharp/README.md b/source/csharp/README.md
index f26f7a6f..8fd75b7e 100644
--- a/source/csharp/README.md
+++ b/source/csharp/README.md
@@ -128,10 +128,10 @@ It also allows converting from a vector to spherical (angular) coordinates and b
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
-- **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
+- **EQJ = J2000 Mean Equator**: Uses the Earth's equator on January 1, 2000, at noon UTC.
 - **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
 - **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
-- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
+- **ECL = J2000 Mean Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
@@ -147,22 +147,22 @@ these are used in function and type names.
 | [EquatorFromVector](#Astronomy.EquatorFromVector) | Given an equatorial vector, calculates equatorial angular coordinates. |
 | [VectorFromHorizon](#Astronomy.VectorFromHorizon) | Given apparent angular horizontal coordinates, calculates horizontal vector. |
 | [HorizonFromVector](#Astronomy.HorizonFromVector) | Given a vector in horizontal orientation, calculates horizontal angular coordinates. |
-| [Rotation_EQD_EQJ](#Astronomy.Rotation_EQD_EQJ) | Calculates a rotation matrix from equatorial of date (EQD) to equatorial J2000 (EQJ). |
-| [Rotation_EQD_ECT](#Astronomy.Rotation_EQD_ECT) | Calculates a rotation matrix from equatorial of date (EQD) to true ecliptic of date (ECT). |
-| [Rotation_EQD_ECL](#Astronomy.Rotation_EQD_ECL) | Calculates a rotation matrix from equatorial of date (EQD) to ecliptic J2000 (ECL). |
-| [Rotation_EQD_HOR](#Astronomy.Rotation_EQD_HOR) | Calculates a rotation matrix from equatorial of date (EQD) to horizontal (HOR). |
-| [Rotation_EQJ_EQD](#Astronomy.Rotation_EQJ_EQD) | Calculates a rotation matrix from equatorial J2000 (EQJ) to equatorial of date (EQD). |
-| [Rotation_EQJ_ECL](#Astronomy.Rotation_EQJ_ECL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_HOR](#Astronomy.Rotation_EQJ_HOR) | Calculates a rotation matrix from equatorial J2000 (EQJ) to horizontal (HOR). |
+| [Rotation_EQD_EQJ](#Astronomy.Rotation_EQD_EQJ) | Calculates a rotation matrix from equator of date (EQD) to J2000 mean equator (EQJ). |
+| [Rotation_EQD_ECT](#Astronomy.Rotation_EQD_ECT) | Calculates a rotation matrix from equator of date (EQD) to true ecliptic of date (ECT). |
+| [Rotation_EQD_ECL](#Astronomy.Rotation_EQD_ECL) | Calculates a rotation matrix from equator of date (EQD) to ecliptic J2000 (ECL). |
+| [Rotation_EQD_HOR](#Astronomy.Rotation_EQD_HOR) | Calculates a rotation matrix from equator of date (EQD) to horizontal (HOR). |
+| [Rotation_EQJ_EQD](#Astronomy.Rotation_EQJ_EQD) | Calculates a rotation matrix from J2000 mean equator (EQJ) to equator of date (EQD). |
+| [Rotation_EQJ_ECL](#Astronomy.Rotation_EQJ_ECL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to ecliptic J2000 (ECL). |
+| [Rotation_EQJ_HOR](#Astronomy.Rotation_EQJ_HOR) | Calculates a rotation matrix from J2000 mean equator (EQJ) to horizontal (HOR). |
 | [Rotation_ECT_EQD](#Astronomy.Rotation_ECT_EQD) | Calculates a rotation matrix from true ecliptic of date (ECT) to equator of date (EQD). |
-| [Rotation_ECL_EQD](#Astronomy.Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial of date (EQD). |
-| [Rotation_ECL_EQJ](#Astronomy.Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial J2000 (EQJ). |
+| [Rotation_ECL_EQD](#Astronomy.Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equator of date (EQD). |
+| [Rotation_ECL_EQJ](#Astronomy.Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to J2000 mean equator (EQJ). |
 | [Rotation_ECL_HOR](#Astronomy.Rotation_ECL_HOR) | Calculates a rotation matrix from ecliptic J2000 (ECL) to horizontal (HOR). |
-| [Rotation_HOR_EQD](#Astronomy.Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equatorial of date (EQD). |
+| [Rotation_HOR_EQD](#Astronomy.Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equator of date (EQD). |
 | [Rotation_HOR_EQJ](#Astronomy.Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 equatorial (EQJ). |
 | [Rotation_HOR_ECL](#Astronomy.Rotation_HOR_ECL) | Calculates a rotation matrix from horizontal (HOR) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_GAL](#Astronomy.Rotation_EQJ_GAL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to galactic (GAL). |
-| [Rotation_GAL_EQJ](#Astronomy.Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to equatorial J2000 (EQJ). |
+| [Rotation_EQJ_GAL](#Astronomy.Rotation_EQJ_GAL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to galactic (GAL). |
+| [Rotation_GAL_EQJ](#Astronomy.Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to J2000 mean equator (EQJ). |
 
 ### Gravitational simulation of small bodies
 
diff --git a/source/js/README.md b/source/js/README.md
index 11bf0749..43d3143f 100644
--- a/source/js/README.md
+++ b/source/js/README.md
@@ -124,10 +124,10 @@ It also allows converting from a vector to spherical (angular) coordinates and b
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
-- **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
+- **EQJ = J2000 Mean Equator**: Uses the Earth's equator on January 1, 2000, at noon UTC.
 - **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
 - **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
-- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
+- **ECL = J2000 Mean Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
@@ -143,20 +143,20 @@ these are used in function and type names.
 | [EquatorFromVector](#EquatorFromVector) | Given an equatorial vector, calculates equatorial angular coordinates. |
 | [VectorFromHorizon](#VectorFromHorizon) | Given apparent angular horizontal coordinates, calculates horizontal vector. |
 | [HorizonFromVector](#HorizonFromVector) | Given a vector in horizontal orientation, calculates horizontal angular coordinates. |
-| [Rotation_EQD_EQJ](#Rotation_EQD_EQJ) | Calculates a rotation matrix from equatorial of-date (EQD) to equatorial J2000 (EQJ). |
-| [Rotation_EQD_ECL](#Rotation_EQD_ECL) | Calculates a rotation matrix from equatorial of-date (EQD) to ecliptic J2000 (ECL). |
-| [Rotation_EQD_HOR](#Rotation_EQD_HOR) | Calculates a rotation matrix from equatorial of-date (EQD) to horizontal (HOR). |
-| [Rotation_EQJ_EQD](#Rotation_EQJ_EQD) | Calculates a rotation matrix from equatorial J2000 (EQJ) to equatorial of-date (EQD). |
-| [Rotation_EQJ_ECL](#Rotation_EQJ_ECL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_HOR](#Rotation_EQJ_HOR) | Calculates a rotation matrix from equatorial J2000 (EQJ) to horizontal (HOR). |
-| [Rotation_ECL_EQD](#Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial of-date (EQD). |
-| [Rotation_ECL_EQJ](#Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial J2000 (EQJ). |
+| [Rotation_EQD_EQJ](#Rotation_EQD_EQJ) | Calculates a rotation matrix from equator of date (EQD) to J2000 mean equator (EQJ). |
+| [Rotation_EQD_ECL](#Rotation_EQD_ECL) | Calculates a rotation matrix from equator of date (EQD) to ecliptic J2000 (ECL). |
+| [Rotation_EQD_HOR](#Rotation_EQD_HOR) | Calculates a rotation matrix from equator of date (EQD) to horizontal (HOR). |
+| [Rotation_EQJ_EQD](#Rotation_EQJ_EQD) | Calculates a rotation matrix from J2000 mean equator (EQJ) to equator of date (EQD). |
+| [Rotation_EQJ_ECL](#Rotation_EQJ_ECL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to ecliptic J2000 (ECL). |
+| [Rotation_EQJ_HOR](#Rotation_EQJ_HOR) | Calculates a rotation matrix from J2000 mean equator (EQJ) to horizontal (HOR). |
+| [Rotation_ECL_EQD](#Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equator of date (EQD). |
+| [Rotation_ECL_EQJ](#Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to J2000 mean equator (EQJ). |
 | [Rotation_ECL_HOR](#Rotation_ECL_HOR) | Calculates a rotation matrix from ecliptic J2000 (ECL) to horizontal (HOR). |
-| [Rotation_HOR_EQD](#Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equatorial of-date (EQD). |
-| [Rotation_HOR_EQJ](#Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 equatorial (EQJ). |
+| [Rotation_HOR_EQD](#Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equator of date (EQD). |
+| [Rotation_HOR_EQJ](#Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 mean equator (EQJ). |
 | [Rotation_HOR_ECL](#Rotation_HOR_ECL) | Calculates a rotation matrix from horizontal (HOR) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_GAL](#Rotation_EQJ_GAL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to galactic (GAL). |
-| [Rotation_GAL_EQJ](#Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to equatorial J2000 (EQJ). |
+| [Rotation_EQJ_GAL](#Rotation_EQJ_GAL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to galactic (GAL). |
+| [Rotation_GAL_EQJ](#Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to J2000 mean equator (EQJ). |
 
 ### Gravitational simulation of small bodies
 
diff --git a/source/kotlin/README.md b/source/kotlin/README.md
index 8962a96c..cf096b09 100644
--- a/source/kotlin/README.md
+++ b/source/kotlin/README.md
@@ -52,10 +52,10 @@ It also allows converting from a vector to spherical (angular) coordinates and b
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
-- **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
+- **EQJ = J2000 Mean Equator**: Uses the Earth's equator on January 1, 2000, at noon UTC.
 - **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
 - **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
-- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
+- **ECL = J2000 Mean Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
diff --git a/source/python/README.md b/source/python/README.md
index 47e36172..f4bfbe73 100644
--- a/source/python/README.md
+++ b/source/python/README.md
@@ -141,10 +141,10 @@ It also allows converting from a vector to spherical (angular) coordinates and b
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
-- **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
+- **EQJ = J2000 Mean Equator**: Uses the Earth's equator on January 1, 2000, at noon UTC.
 - **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
 - **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
-- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
+- **ECL = J2000 Mean Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
@@ -160,20 +160,22 @@ these are used in function and type names.
 | [EquatorFromVector](#EquatorFromVector) | Given an equatorial vector, calculates equatorial angular coordinates. |
 | [VectorFromHorizon](#VectorFromHorizon) | Given apparent angular horizontal coordinates, calculates horizontal vector. |
 | [HorizonFromVector](#HorizonFromVector) | Given a vector in horizontal orientation, calculates horizontal angular coordinates. |
-| [Rotation_EQD_EQJ](#Rotation_EQD_EQJ) | Calculates a rotation matrix from equatorial of-date (EQD) to equatorial J2000 (EQJ). |
-| [Rotation_EQD_ECL](#Rotation_EQD_ECL) | Calculates a rotation matrix from equatorial of-date (EQD) to ecliptic J2000 (ECL). |
-| [Rotation_EQD_HOR](#Rotation_EQD_HOR) | Calculates a rotation matrix from equatorial of-date (EQD) to horizontal (HOR). |
-| [Rotation_EQJ_EQD](#Rotation_EQJ_EQD) | Calculates a rotation matrix from equatorial J2000 (EQJ) to equatorial of-date (EQD). |
-| [Rotation_EQJ_ECL](#Rotation_EQJ_ECL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_HOR](#Rotation_EQJ_HOR) | Calculates a rotation matrix from equatorial J2000 (EQJ) to horizontal (HOR). |
-| [Rotation_ECL_EQD](#Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial of-date (EQD). |
-| [Rotation_ECL_EQJ](#Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equatorial J2000 (EQJ). |
+| [Rotation_EQD_EQJ](#Rotation_EQD_EQJ) | Calculates a rotation matrix from equator of date (EQD) to J2000 mean equator (EQJ). |
+| [Rotation_EQD_ECT](#Rotation_EQD_ECT) | Calculates a rotation matrix from equator of date (EQD) to true ecliptic of date (ECT). |
+| [Rotation_EQD_ECL](#Rotation_EQD_ECL) | Calculates a rotation matrix from equator of date (EQD) to ecliptic J2000 (ECL). |
+| [Rotation_EQD_HOR](#Rotation_EQD_HOR) | Calculates a rotation matrix from equator of date (EQD) to horizontal (HOR). |
+| [Rotation_EQJ_EQD](#Rotation_EQJ_EQD) | Calculates a rotation matrix from J2000 mean equator (EQJ) to equator of date (EQD). |
+| [Rotation_EQJ_ECL](#Rotation_EQJ_ECL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to ecliptic J2000 (ECL). |
+| [Rotation_EQJ_HOR](#Rotation_EQJ_HOR) | Calculates a rotation matrix from J2000 mean equator (EQJ) to horizontal (HOR). |
+| [Rotation_ECT_EQD](#Rotation_ECT_EQD) | Calculates a rotation matrix from true ecliptic of date (ECT) to equator of date (EQD). |
+| [Rotation_ECL_EQD](#Rotation_ECL_EQD) | Calculates a rotation matrix from ecliptic J2000 (ECL) to equator of date (EQD). |
+| [Rotation_ECL_EQJ](#Rotation_ECL_EQJ) | Calculates a rotation matrix from ecliptic J2000 (ECL) to J2000 mean equator (EQJ). |
 | [Rotation_ECL_HOR](#Rotation_ECL_HOR) | Calculates a rotation matrix from ecliptic J2000 (ECL) to horizontal (HOR). |
-| [Rotation_HOR_EQD](#Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equatorial of-date (EQD). |
+| [Rotation_HOR_EQD](#Rotation_HOR_EQD) | Calculates a rotation matrix from horizontal (HOR) to equator of date (EQD). |
 | [Rotation_HOR_EQJ](#Rotation_HOR_EQJ) | Calculates a rotation matrix from horizontal (HOR) to J2000 equatorial (EQJ). |
 | [Rotation_HOR_ECL](#Rotation_HOR_ECL) | Calculates a rotation matrix from horizontal (HOR) to ecliptic J2000 (ECL). |
-| [Rotation_EQJ_GAL](#Rotation_EQJ_GAL) | Calculates a rotation matrix from equatorial J2000 (EQJ) to galactic (GAL). |
-| [Rotation_GAL_EQJ](#Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to equatorial J2000 (EQJ). |
+| [Rotation_EQJ_GAL](#Rotation_EQJ_GAL) | Calculates a rotation matrix from J2000 mean equator (EQJ) to galactic (GAL). |
+| [Rotation_GAL_EQJ](#Rotation_GAL_EQJ) | Calculates a rotation matrix from galactic (GAL) to J2000 mean equator (EQJ). |
 
 ### Gravitational simulation of small bodies
 
@@ -2553,6 +2555,25 @@ and so that north represents the direction where azimuth = 0.
 
 ---
 
+<a name="Rotation_ECT_EQD"></a>
+### Rotation_ECT_EQD(time)
+
+**Calculates a rotation matrix from true ecliptic of date (ECT) to equator of date (EQD).**
+
+This is one of the family of functions that returns a rotation matrix
+for converting from one orientation to another.
+Source: ECT = true ecliptic of date.
+Target: EQD = equator of date.
+
+| Type | Parameter | Description |
+| --- | --- | --- |
+| [`Time`](#Time) | `time` | The date and time of the ecliptic/equator conversion. |
+
+**Returns**: [`RotationMatrix`](#RotationMatrix)
+A rotation matrix that converts ECT to EQD.
+
+---
+
 <a name="Rotation_EQD_ECL"></a>
 ### Rotation_EQD_ECL(time)
 
@@ -2572,6 +2593,25 @@ A rotation matrix that converts EQD to ECL.
 
 ---
 
+<a name="Rotation_EQD_ECT"></a>
+### Rotation_EQD_ECT(time)
+
+**Calculates a rotation matrix from equator of date (EQD) to true ecliptic of date (ECT).**
+
+This is one of the family of functions that returns a rotation matrix
+for converting from one orientation to another.
+Source: EQD = equator of date.
+Target: ECT = true ecliptic of date.
+
+| Type | Parameter | Description |
+| --- | --- | --- |
+| [`Time`](#Time) | `time` | The date and time of the equator/ecliptic conversion. |
+
+**Returns**: [`RotationMatrix`](#RotationMatrix)
+A rotation matrix that converts EQD to ECT.
+
+---
+
 <a name="Rotation_EQD_EQJ"></a>
 ### Rotation_EQD_EQJ(time)
 
diff --git a/source/python/astronomy/astronomy.py b/source/python/astronomy/astronomy.py
index cf41d900..b7a2c593 100644
--- a/source/python/astronomy/astronomy.py
+++ b/source/python/astronomy/astronomy.py
@@ -7596,6 +7596,63 @@ def Rotation_GAL_EQJ():
         [-0.8676668813529025, -0.1980677870294097, +0.4559861124470794]
     ])
 
+def Rotation_ECT_EQD(time):
+    """Calculates a rotation matrix from true ecliptic of date (ECT) to equator of date (EQD).
+
+    This is one of the family of functions that returns a rotation matrix
+    for converting from one orientation to another.
+    Source: ECT = true ecliptic of date.
+    Target: EQD = equator of date.
+
+    Parameters
+    ----------
+    time : Time
+        The date and time of the ecliptic/equator conversion.
+
+    Returns
+    -------
+    RotationMatrix
+        A rotation matrix that converts ECT to EQD.
+    """
+    et = _e_tilt(time)
+    tobl = math.radians(et.tobl)
+    c = math.cos(tobl)
+    s = math.sin(tobl)
+    return RotationMatrix([
+        [1.0, 0.0, 0.0],
+        [0.0,  +c,  +s],
+        [0.0,  -s,  +c]
+    ])
+
+def Rotation_EQD_ECT(time):
+    """Calculates a rotation matrix from equator of date (EQD) to true ecliptic of date (ECT).
+
+    This is one of the family of functions that returns a rotation matrix
+    for converting from one orientation to another.
+    Source: EQD = equator of date.
+    Target: ECT = true ecliptic of date.
+
+    Parameters
+    ----------
+    time : Time
+        The date and time of the equator/ecliptic conversion.
+
+    Returns
+    -------
+    RotationMatrix
+        A rotation matrix that converts EQD to ECT.
+    """
+    et = _e_tilt(time)
+    tobl = math.radians(et.tobl)
+    c = math.cos(tobl)
+    s = math.sin(tobl)
+    return RotationMatrix([
+        [1.0, 0.0, 0.0],
+        [0.0,  +c,  -s],
+        [0.0,  +s,  +c]
+    ])
+
+
 class ConstellationInfo:
     """Reports the constellation that a given celestial point lies within.