[pycalcal] push by enrico.spinielli - some text on coords on 2010-02-07 16:26 GMT

[pyca...@googlecode.com]

Revision: afa624a090
Author: Enrico Spinielli <enrico.s...@gmail.com>
Date: Sun Feb 7 08:26:03 2010
Log: some text on coords
http://code.google.com/p/pycalcal/source/detail?r=afa624a090

Modified:
/pycalcal.nw

=======================================
--- /pycalcal.nw Sat Feb 6 06:37:45 2010
+++ /pycalcal.nw Sun Feb 7 08:26:03 2010
@@ -3182,13 +3182,13 @@
\label{sec:astro}
The location of an object in the sky is determined by celestial
coordinates, analogous to the latitude and longotude for the location
-of a position of Earth.
+of a position on Earth.
\subsection{$Alt-az$ Coordinate systems}
\label{sec:alt-az}
The alt-az is a topocentric (i.e. as seen from the observer's
place on the Earth's surface) celestial coordinate system.
It uses the horizon as its fundamental circle which divides the sky in
-two emispheres. The pole of the upper hemisphere is called the zenith,
+two hemispheres. The pole of the upper hemisphere is called the zenith,
while the one of the lower hemisphere is called nadir. These are
defined by the local vertical (using a plumb-line or similar).
The point of origin on the horizon is determined by the intersection
@@ -3203,10 +3203,10 @@
\begin{figure}[h]
\rule{\textwidth}{0.005in}
\begin{center}
- \includegraphics[width=\textwidth]{fig_alt-az.png}
+ \includegraphics[width=0.9\textwidth]{fig_alt-az.png}
\caption{Alt-az coordinate system. $N$ is the North (Celestial)
Pole;
- $x$ points at the intersection between Greenwich meridian and
+ $i$ points at the intersection between Greenwich meridian and
the equator;
$A$ is the azimuth of the celestial body $B$ as seen from
observer positioned in $P$ (at geographical longitude $L$ and
@@ -3240,13 +3240,15 @@

Any great circle between the NCP and the SCP is a meridian.
The one which also passes through the zenith and the nadir
-is "the" celestial meridian, or the observer's meridian.
+is ''the`` celestial meridian, or the observer's meridian.
(It is identical to the principal vertical.)
This provides our new zero-point;
in this case, we use the point where it crosses the southern half of
the equator.

-
+The Hour Angle ($HA$ or $H$) of object X is the angular distance between
the
+meridian of X and the celestial meridian.
+It is measured westwards in hours, 0h-24h, since the Earth rotates 360° in
24 hours.


\subsection{$RA-dec$ Coordinate systems}
@@ -3256,7 +3258,7 @@
\begin{figure}[h]
\rule{\textwidth}{0.005in}
\begin{center}
- \includegraphics{fig_ra-dec-0.pdf}
+ \includegraphics[width=0.9\textwidth]{fig_ra-dec-0.pdf}
\caption{RA-dec coordinate system. $N^*$ is the North pole of the
ecliptic; $N$ is the North Celestial Pole; $\vernal$ is the
first point of Aries and the zero-point for this coordinate
@@ -3280,7 +3282,7 @@
\begin{figure}[h]
\rule{\textwidth}{0.005in}
\begin{center}
- \includegraphics{fig_ecliptic-0.pdf}
+ \includegraphics[width=0.9\textwidth]{fig_ecliptic-0.pdf}
\caption{Celestial coordinate system. $N^*$ is the North pole of the
ecliptic; $N$ is the North Celestial Pole; $\vernal$ is the first
point of Aries or the ascending node of the mean
@@ -3325,9 +3327,9 @@
def `equatorial_from_ecliptical(longitude, latitude, obliquity):
"""Convert ecliptical coordinates (in degrees) to equatorial ones.
'longitude' is the ecliptical longitude,
- 'latitude' is the starting ecliptical latitude and
+ 'latitude' is the ecliptical latitude and
'obliquity' is the obliquity of the ecliptic.
- NOTE: resuting ra and declination will be referred to the same equinox
+ NOTE: resuting 'ra' and 'declination' will be referred to the same
equinox
as the one of input ecliptical longitude and latitude.
"""
co = cos_degrees(obliquity)
@@ -3352,11 +3354,11 @@
<<time and astronomy>>=
def `horizontal_from_equatorial(H, declination, latitude):
"""Convert equatorial coordinates (in degrees) to horizontal ones.
- Return azimuth and altitude.
- 'H' is the hour angle,
+ Return 'azimuth' and 'altitude'.
+ 'H' is the local hour angle,
'declination' is the declination,
'latitude' is the observer's geographic latitude.
- NOTE: azimuth is measured westward from the South.
+ NOTE: 'azimuth' is measured westward from the South.
NOTE: This is not a good formula for using near the poles.
"""
ch = cos_degrees(H)
@@ -3380,11 +3382,11 @@
<<time and astronomy>>=
def `equatorial_from_horizontal(A, h, phi):
"""Convert equatorial coordinates (in degrees) to horizontal ones.
- Return hour angle and declination.
+ Return 'local hour angle' and 'declination'.
'A' is the azimuth,
'h' is the altitude,
- 'phi' is the observer's geographic latitude.
- NOTE: azimuth is measured westward from the South.
+ 'phi' is the observer's geographical latitude.
+ NOTE: 'azimuth' is measured westward from the South.
"""
H = degrees_from_radians(
atan2(sin_degrees(A),
@@ -7742,7 +7744,7 @@

%%%%%%%%
\subsection*{Using dates and times}
-Convert \texttt{30^{th} Jan 1967 11:20:00 UT} to RD
+Convert \texttt{$30^{th}$ Jan 1967 11:20:00 UT} to RD
\begin{verbatim}
>>> d=gregorian_date(1967, JANUARY, 30)
>>> t=time_from_clock([11, 20, 00])