def eq2horz(obslat,obslon,doi,RA,dec):
'''
Given:
observer latitude and longitude
event time
RA and dec
returns the Horizontal Geocentric Coordinates.
All angles given in radians
obslat - observer latitude
obslong - observer longitude
doi - datetime object of interest
RA - right ascension of event
dec - declination of event
'''
LST = dttm2LST(doi,obslon)
H = 2.*pi*remainder(LST,24.)/24. - RA
sinalt = sin(dec)*sin(obslat) + cos(dec)*cos(obslat)*cos(H)
alt = arcsin(sinalt)
sinaz = - sin(H)*cos(dec) / cos(alt)
cosaz = ( sin(dec) - sin(obslat)*sinalt ) / (cos(obslat)*cos(alt))
az = arctan2(sinaz,cosaz)
return alt, az
def horz2eq(obslat,obslon,doi,alt,az):
'''
Given:
observer latitude and longitude
event time
RA and dec
returns the Equatorial Coordinates.
All angles given in radians
obslat - observer latitude
obslong - observer longitude
doi - datetime object of interest
alt - altitude angle of event
az - azimuthal angle of event
'''
LST = dttm2LST(doi,obslon)
sindec = sin(alt)*sin(obslat) + cos(alt)*cos(obslat)*cos(az)
dec = arcsin(sindec)
cosdec = cos(dec)
sinHA = - sin(az)*cos(alt) / cosdec
cosHA = ( sin(alt) - sindec * sin(obslat)) / (cosdec*cos(obslat))
HA = arctan2(sinHA,cosHA)
RA = 2.*pi*remainder(LST,24.)/24. - HA
return RA, dec
