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A text box entitled Astronomical Data provides information needed for
tracking the sun or moon, compensating for EME Doppler shift, and
estimating EME Doppler spread and path degradation. Toggle the
*Astronomical data* on the *View* menu to display or hide this window.

image::AstroData_2.png[align="center",alt="Astronomical Data"]

Available information includes the current UTC *Date* and *Time*; *Az*
and *El*, azimuth and elevation of the moon at your own location, in
degrees; *SelfDop*, *Width*, and *Delay*, the Doppler shift, full
limb-to-limb Doppler spread in Hz, and delay of your own EME echoes in
seconds; and *DxAz* and *DxEl*, *DxDop*, and *DxWid*, corresponding
parameters for a station located at the *DX Grid* entered on the main
window.  These numbers are followed by *Dec*, the declination of the
moon; *SunAz* and *SunEl*, the azimuth and elevation of the Sun;
*Freq*, your stated operating frequency in MHz; *Tsky*, the estimated
sky background temperature in the direction of the moon, scaled to the
operating frequency; *Dpol*, the spatial polarization offset in
degrees; *MNR*, the maximum non-reciprocity of the EME path in dB,
owing to a combination of Faraday rotation and spatial polarization;
*Dist*, the distance from your location to the moon, in km;
and finally *Dgrd*, an estimate of the signal degradation in dB,
relative to the best possible time with the moon at perigee in a cold
part of the sky.

On the higher microwave bands, where Faraday rotation is minimal and
linear polarization is often used, spatial offset reduces signal
levels. Some stations have implemented mechanical polarisation
adjustment to overcome this loss. The amount of rotation needed is
predicted in real time by the value of *Dpol*.  Positive Dpol means
that the antenna should be rotated in a clockwise direction looking
from behind the antenna towards the moon.  For a dish antenna, the
feed should similarly be rotated clockwise looking into the mouth of
the feed. A negative value for Dpol means a counterclockwise rotation.


The state-of-the-art for establishing three-dimensional locations of
the sun, moon, and planets at a specified time is embodied in a
numerical model of the solar system maintained at the Jet Propulsion
Laboratory. The model has been numerically integrated to produce
tabular data that can be interpolated with very high accuracy. For
example, the celestial coordinates of the moon or a planet can be
determined at a specified time to within about 0.0000003 degrees. The
JPL ephemeris tables and interpolation routines have been incorporated
into _WSJT-X_.  Further details on accuracy, especially concerning
calculated EME Doppler shifts, are described in {lunarEchoes} for
November-December, 2016.

The sky background temperatures reported by _WSJT-X_ are derived from
the all-sky 408 MHz map of Haslam et al. (Astronomy and Astrophysics
Supplement Series, 47, 1, 1982), scaled by frequency to the -2.6
power. This map has angular resolution of about 1 degree, and of
course most amateur EME antennas have much broader beamwidths than
this. Your antenna will therefore smooth out the hot spots
considerably, and the observed extremes of sky temperature will be
less. Unless you understand your sidelobes and ground reflections
extremely well, it is unlikely that more accurate sky temperatures
would be of much practical use.
