MoonlightMap

class ctapointing.exposure.MoonlightMap

Bases: object

Implements the calculation of a moonlight brightness map, following equation (15) of the paper by Krisciunas et al. (doi:10.1086/132921)

The brightness is calculated for a given array of altaz coordinates. Time of observation and observer’s location are extracted from these coordinates.

Brightness is in units photon flux per steradian.

Methods Summary

`B`(coords_altaz, moon_altaz, alpha[, k])	Equation (15) of Krisciunas et al. Only valid for moon above the horizon.
`I`(alpha)	Illuminance of the moon as function of moon phase angle.
`X`(zenith)	Atmospheric absorption as function of zenith angle
`f`(rho)	Atmospheric scattering function as function of the distance between moon and observation.
`process`(coords)	Calculate moon brightness map.

Methods Documentation

B(coords_altaz, moon_altaz, alpha, k=0.172)

Equation (15) of Krisciunas et al. Only valid for moon above the horizon. If moon is below horizon, brightness 0 is returned.

Parameters:

coords_altaz (SkyCoord) – altaz coordinates for which to calculate brightness
moon_altaz (SkyCoord) – altaz coordinates of the moon
alpha (Angle) – phase angle of the moon
k (float) – V-band extinction in units of mag/air mass

:returns photon flux map :rtype array of astropy.Quantity

I(alpha): Illuminance of the moon as function of moon phase angle. :param Angle alpha: phase angle of the moon :returns moon illuminance :rtype: float

X(zenith): Atmospheric absorption as function of zenith angle

f(rho): Atmospheric scattering function as function of the distance between moon and observation. :param Angle rho: (array of) separations to the moon :returns amount of scattered light :rtpye (array of) float

process(coords)

Calculate moon brightness map.

Returns:: brightness list, sun/moon coordinates, moon phase
Return type:: array of astropy.Quantity, two astropy.SkyCoords, astropy.Angle