This adds six methods to caput.time.Observer to calculate (solar/lunar) (transits/risings/settings).
These functions are originally from ch_util.ephemeris where they originally worked only on the chimeObserver. They've since been enhanced to use any Observer, so there's no reason now not to have them in the Observer object directly.
CHANGE FROM CH_UTIL VERSION
There is one major change to these functions from what was in ch_util.ephemeris: instead of a diameter of 0.6 degrees = 36 arcminutes, these methods now use a diameter of 100 arcminutes.
This means these functions now compute astronomical sun/moon rise/set, which is conventionally taken to occur when the centre of the sun/moon is 50 arcminutes below the horizon.
The 50 arcminute number comes from a solar/lunar radius of 16 arcminutes plus 34 arcminutes of atmospheric refraction at the horizon.
This adds six methods to
caput.time.Observerto calculate (solar/lunar) (transits/risings/settings).These functions are originally from
ch_util.ephemeriswhere they originally worked only on thechimeObserver. They've since been enhanced to use anyObserver, so there's no reason now not to have them in theObserverobject directly.CHANGE FROM CH_UTIL VERSION
There is one major change to these functions from what was in
ch_util.ephemeris: instead of adiameterof 0.6 degrees = 36 arcminutes, these methods now use adiameterof 100 arcminutes.This means these functions now compute astronomical sun/moon rise/set, which is conventionally taken to occur when the centre of the sun/moon is 50 arcminutes below the horizon.
The 50 arcminute number comes from a solar/lunar radius of 16 arcminutes plus 34 arcminutes of atmospheric refraction at the horizon.
This change fixes the 3-minute discrepancy Mateus noticed when these functions were first ported from PyEphem (which does account for atmospheric refraction) to skyfield (which does not account for the refraction), here: https://github.com/chime-experiment/ch_util_private/commit/b505cf099c1de4eb39f2e34828e8da545d3db8e0
Transit times are unchanged: the atmospheric refraction at zenith is zero.