oracular (3) Astro::Time.3pm.gz
NAME
Astro::Time - Time based astronomical routines
SYNOPSIS
use Astro::Time; $dayno = cal2dayno($day, $month, $year); print "It's a leap year!\n" if (leap($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 calendar 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 Chris.Phillips@csiro.au
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 $Astro::Time::StrSep) Note: The behavior can be modified by the following two variables: $Astro::Time::StrZero Minimum number of leading digits (zero padded if needed) $Astro::Time::StrSep (Overridden by optional fourth argument) 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 degrees) $time Day fraction $hour Hours $minutes Minutes $second Seconds $mode 'H' or 'D' to interpret as hours or degrees (default hours) time2hms ($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 (universal 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 (universal 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 mjd2time $str = mjd2time($mjd); $str = mjd2time($mjd, $np); Converts a Modified Julian day to a formatted string $mjd Modified Julian day $str Formatted time $np Number of significant digits for fraction of a sec. Default 0 mjd2vextime $str = mjd2vextime($mjd); $str = mjd2vextime($mjd, $np); Converts a Modified Julian day to a vex formatted string $mjd Modified Julian day $str Formatted time $np Number of significant digits for fraction of a sec. Default 0 mjd2epoch $time = mjd2epoch($mjd); Converts a Modified Julian day to unix Epoch (seconds sinve 1 Jan 1970) Rounded to the nearest second $mjd Modified Julian day $tie Seconds since 1 Jan 1970 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 accuracy 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 corresponding 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 conversion $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) (seconds) $mjd The modified Julian day corresponding to $lmst on $dayno month2str $monthstr = month2str($month); $longmonthstr = month2str($month,1); This routine returns the name of the given month (as a number 1..12), where 1 is January. The default is a 3 character version of the month ('Jan', 'Feb', etc) in the second form the full month is returned The required inputs are : $month - The month in question with 1 == January. mjd2weekday $weekday = mjd2weekday($mjd); Returns the weekday correspondig to the given MJD. 0 ==> Monday. May not work for historical dates. $mjd Modified Julian day (JD-2400000.5) mjd2weekdaystr $weekdaystr = mjd2weekdaystr($mjd); Returns the name of the weekday correspondig to the given MJD. May not work for historical dates. $mjd Modified Julian day (JD-2400000.5) str2month $month = month2str($monthstr); Given the name of a month (in English), this routine returns the an integer between 1 and 12, where 1 is January. Full month names of 3 character abbreviations are acceptable. Minumum matching (e.g. "Marc") is not supported. The required inputs are : $month - Name of the month ('Jan', 'January', 'Feb', 'February' etc)