astro::time(3)

NAME

Astro::Time - Time based astronomical routines

SYNOPSIS

use Astro::Time;
$dayno = cal2dayno($day, $month, $year);
print "It's a leap year!0 if (leap($year));
$lmst = mjd2lst($mjd, $longitude, $dUT1);
$turns = str2turn($string, 'H');
$str = turn2str($turn, 'D', $sig);

DESCRIPTION

Astro::Time contains an assorted set Perl routines for
time based conversions, such as conversion between calen
dar dates and Modified Julian day and conversion of UT to
local sidereal time. Include are routines for conversion
between numerical and string representation of angles.

AUTHOR

Chris Phillips phillips@jive.nl

FUNCTIONS turn2str

$str = turn2str($turn, $mode, $sig);
$str = turn2str($turn, $mode, $sig, $strsep);
Convert fraction of a turn into string representation: $turn Angle in turns
$mode Mode of string to convert to:
'H' for hours
'D' for degrees; $sig number of significant figures
$strsep String separator (override for default $As; tro::Time::StrSep) Note:
The behavior can be modified by the following two variables:: $Astro::Time::ZeroStr Minimum number of leading digits (zero; padded
if needed); $Astro::Time::StrSep (Overridden by optional fourth argu; ment)
Deliminator used in string (Default ':')
This may also equal one of a number of special values:
'HMS' 12H45M12.3S or 170D34M56.2S
'hms' 12h45m12.3s or 170d34m56.2s
'deg' 170d34'56.2"
deg2str
$str=deg2str($deg, $mode, $sig);
Convert degrees into string representation: $deg angle in degrees
$mode mode of string to convert to:
'H' for hours
'D' for degrees; $sig number of significant figures
See note for turn2str
rad2str: $str=rad2str($rad, $mode, $sig);
Convert radians into string representation: $rad angle in radians
$mode mode of string to convert to:
'H' for hours
'D' for degrees; $sig is number of significant figures
See note for turn2str
str2turn: $turns = str2turn($string,$mode);
Convert angle from string representation into fraction of a turn: $string a : or space delimited angle
$mode type of angle
'H' if $string is in hours,min,sec
'D' if $string is in deg,arcmin,arcsec; The format of $string can be fairly flexible e.g.:
12.2
12:34
12:34:45.1; -23 34 12.3
-34 34.3
Note: You cannot mix spaces and :
str2deg: $degrees=str2deg($string,$mode);
Convert angle from string representation into degrees: $string a : or space delimited angle
$mode 'H' if $string is in hours,min,sec
'D' if $string is in deg,arcmin,arcsec; See note for str2turn
str2rad: $radians=str2rad($string,$mode);
Convert angle from string representation into radians: $string a : or space delimited angle
$mode 'H' if $string is in hours,min,sec
'D' if $string is in deg,arcmin,arcsec; See note for str2turn
hms2time: ($time) = hms2time($hour, $minute, $second);
($time) = hms2time($hour, $minute, $second, $mode);
Returns the day fraction given hours minutes and seconds (or de
grees): $time Day fraction
$hour Hours
$minutes Minutes
$second Seconds
$mode 'H' or 'D' to interpret as hours or degrees (de; fault
hours)
time2hms
($sign, $hour, $minute, $second) = time2hms($time, $mode,
$sig);
Returns hours (or degrees), minutes and seconds given the day
fraction: $sign Sign of angle ('+' or '-')
$hour Hours
$minutes Minutes
$second Seconds
$time Day fraction
$mode Return degrees or Hours?
'H' for hours
'D' for degrees; $sig Number of significant digits for $second
deg2rad
$rad=deg2rad($deg);
Convert degrees to radians
rad2deg: $deg=rad2deg($rad);
Convert radians to degrees
turn2rad: $rad=turn2rad($turn);
Convert turns to radians
rad2turn: $turn=rad2turn($rad);
Convert radians to turns
turn2deg: $deg=turn2deg($turn);
Convert turns to radians
deg2turn: $turn=deg2turn($deg);
Convert degrees to turns
cal2dayno: $dayno = cal2dayno($day, $month, $year);
Returns the day number corresponding to $day of $month in $year.
dayno2cal: ($day, $month) = dayno2cal($dayno, $year);
Return the $day and $month corresponding to $dayno of $year.
leap: $isleapyear = leap($year);
Returns true if $year is a leap year.: $year year in full
yesterday
($dayno, $year) = yesterday($dayno, $year); ($day, $month, $year) = yesterday($day, $month, $year);
Winds back the day number by one, taking account of year wraps.: $dayno Day number of year
$year Year
$month Month
$day Day of month
tomorrow
($dayno, $year) = tomorrow($dayno, $year); ($day, $month, $year) = tomorrow($day, $month, $year);
Advances the day number by one, taking account of year wraps.: $dayno Day number of year
$year Year
$month Month
$day Day of month
mjd2cal
($day, $month, $year, $ut) = mjd2cal($mjd);
Converts a modified Julian day number into calendar date (uni
versal time). (based on the slalib routine sla_djcl).: $mjd Modified Julian day (JD-2400000.5)
$day Day of the month.
$month Month of the year.
$year Year
$ut UT day fraction
cal2mjd
$mjd = cal2mjd($day, $month, $year, $ut);
Converts a calendar date (universal time) into modified Julian
day number.: $day Day of the month.
$month Month of the year.
$year Year
$ut UT dayfraction
$mjd Modified Julian day (JD-2400000.5)
mjd2dayno
($dayno, $year, $ut) = mjd2dayno($mjd);
Converts a modified Julian day number into year and dayno (uni
versal time).: $mjd Modified Julian day (JD-2400000.5)
$year Year
$dayno Dayno of year
dayno2mjd
$mjd = dayno2mjd($dayno, $year, $ut);
Converts a dayno and year to modified Julian day: $mjd Modified Julian day (JD-2400000.5)
$year Year
$dayno Dayno of year
now2mjd
$mjd = now2mjd()
jd2mjd
$mjd = jd2mjd($jd);
Converts a Julian day to Modified Julian day: $jd Julian day
$mjd Modified Julian day
mjd2jd
$jd = mjd2jd($mjd);
Converts a Modified Julian day to Julian day: $mjd Modified Julian day
$jd Julian day
gst
$gst = gst($mjd); $gmst = gst($mjd, $dUT1); $gtst = gst($mjd, $dUT1, $eqenx);
Converts a modified Julian day number to Greenwich sidereal time: $mjd modified Julian day (JD-2400000.5)
$dUT1 difference between UTC and UT1 (UT1 = UTC + dUT1); (seconds)
$eqenx Equation of the equinoxes (not yet supported)
$gst Greenwich sidereal time (turns)
$gmst Greenwich mean sidereal time (turns)
$gtst Greenwich true sidereal time (turns)
mjd2lst
$lst = mjd2lst($mjd, $longitude); $lmst = mjd2lst($mjd, $longitude, $dUT1); $ltst = mjd2lst($mjd, $longitude, $dUT1, $eqenx);
Converts a modified Julian day number into local sidereal time
(lst), local mean sidereal time (lmst) or local true sidereal time
(ltst). Unless high precisions is required dUT1 can be omitted (it will
always be in the range -0.5 to 0.5 seconds).: $mjd Modified Julian day (JD-2400000.5)
$longitude Longitude for which the LST is required (turns)
$dUT1 Difference between UTC and UT1 (UT1 = UTC +; dUT1)(seconds)
$eqenx Equation of the equinoxes (not yet supported)
$lst Local sidereal time (turns)
$lmst Local mean sidereal time (turns)
$ltst Local true sidereal time (turns)
cal2lst
$lst = cal2lst($day, $month, $year, $ut, $longitude); $lmst = cal2lst($day, $month, $year, $ut, $longitude, $dUT1); $ltst = cal2lst($day, $month, $year, $ut, $longitude, $dUT1,
$eqenx);
Wrapper to mjd2lst using calendar date rather than mjd
dayno2lst: $lst = dayno2lst($dayno, $year, $ut, $longitude);
$lmst = dayno2lst($dayno, $year, $ut, $longitude, $dUT1);
$ltst = dayno2lst($dayno, $year, $ut, $longitude, $dUT1,; $eqenx);
Wrapper to mjd2lst using calendar date rather than mjd
rise: ($lst_rise, $lst_set) = rise($ra, $dec, $obslat, $el_limit);
Return the lst rise and set time of the given source: $lst_rise, $lst_set Rise and set time (turns)
$ra, $dec RA and Dec of source (turns)
$obslat Latitude of observatory (turns)
$el_limit Elevation limit of observatory
(turns, 0 horizontal); Returns 'Circumpolar' if source circumpolar
Returns undef if source never rises; Uses the formula:
cos $z_limit = sin $obslat * sin $dec + cos $obslat * cos $dec
* cos $HA

where:

$z_limit is the zenith angle limit corresponding to $el_limit
$HA is the Hour Angle of the source NOTE: For maximum accura

cy source coordinated should be precessed to
the current date.
lst2mjd
$mjd = lst2mjd($lmst, $dayno, $year, $longitude); $mjd = lst2mjd($lmst, $dayno, $year, $longitude, $dUT1);
This routine calculates the modified Julian day number corre
sponding to the local mean sidereal time $lmst at $longitude, on a given
UT day number ($dayno). Unless high precision is required dUT1
can be omitted.
The required inputs are :: $lmst - The local mean sidereal time (turns)
$dayno - The UT day of year for which to do the conver; sion
$year - The year for which to do the conversion
$longitude - The longitude of the observatory (turns)
$dUT1 - Difference between UTC and UT1 (UT1 = UTC +; dUT1)
(sec

onds); $mjd The modified Julian day corresponding to $lmst; on $dayno

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