FORECAST OF SOURCE VISIBILITY FOR A YEAR
λ =
o
φ =
o
TZ =
Geographical coordinates (in degrees) and timezone (TZ) of location site, by default - for RTT150
α =
h
m
s
δ =
o
'
"
α =
o
δ =
o
Equatorial coordinates of a source (preferrably for the current epoch, but 2000.0 epoch is also possible) in hh:mm:ss &
o
:':" format or in decimal degrees. In the first case
"-" sign
for δ in
o
' " form (second line) should be marked in a
special field
before
o
window. The sign can also be entered in the
o
field itself but in case of -1
o
< δ < 0
o
the value in this field equals to "0" and "-" sign will be lost.
h =
o
Ph =
Δ =
o
Minimal source altitude above horizon (in degrees), maximum allowed phase of the Moon (from 0.0 at the newmoon to 1.0 at the fullmoon) when the night is considered to be dark enough for observing the given source and minimum allowed distance Δ from source to the Moon.
Dates: from
to
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
Start date, final date (in DD/MM format) and the year of forecast
Interval:
days
Interval in days (integer number >= 1) between dates
Comments. λ and φ - geographical coordinates of the site, TZ - its timezone, difference between local zone time (decree/daylight) and Universal Time in hours, =2 h for RTT150. α and δ - equatorial coordinates (epoch 2000.0) of a given source, h - minimal source altitude above horizon, Ph - maximum phase of the Moon.
The resulting forecast is a table of source altitude (in degrees) above horizon for the requested dates with 1 hour step. Universal Time (UTC) and corresponding local time in hours is from the left to the right, dates (before local midnight) are from the top to the bottom.
'-' sign
means that source altitude at this date and time is less than acceptable value h.
White fields
denote bright time (Sun is either above horizon or its altitude under horizon is less than 18 degrees).
Yellow fields
mark presence of the Moon in a phase higher than maximum Ph during the dark time.
Red fields
- presence of the Moon above horizon (with phase > Ph) closer than allowed distance Δ.
Blue fields
show the dark moonless night hours, that is when the Sun is more than 18 degrees below horizon and the Moon is absent or is in a phase less than limiting Ph. Atmospheric refraction is taken into account during the calculations of source and Moon altitudes; position of the Moon is corrected for horizontal parallax.
To avoid unnecessary loss of time for extra calculations it is recommended to print data for the whole year with a large time step at first (for example, using default value of 10 days) and then generate a forecast for a favourable interval of observations only with a small time step. Favourable period resides at the crossing of slanted lines of acceptable source altitudes with a zone of dark (and moonless, if neseccary) time when the source is available for observing at this altitudes during the night.
(C) Copyright
N.Alexandrovich
2002