utils.py 文件源码

def stupidFast_RaDec2AltAz(ra, dec, lat, lon, mjd, lmst=None):
    """
    Convert Ra,Dec to Altitude and Azimuth.

    Coordinate transformation is killing performance. Just use simple equations to speed it up
    and ignore abberation, precesion, nutation, nutrition, etc.

    Parameters
    ----------
    ra : array_like
        RA, in radians.
    dec : array_like
        Dec, in radians. Must be same length as `ra`.
    lat : float
        Latitude of the observatory in radians.
    lon : float
        Longitude of the observatory in radians.
    mjd : float
        Modified Julian Date.

    Returns
    -------
    alt : numpy.array
        Altitude, same length as `ra` and `dec`. Radians.
    az : numpy.array
        Azimuth, same length as `ra` and `dec`. Radians.
    """
    if lmst is None:
        lmst, last = calcLmstLast(mjd, lon)
        lmst = lmst/12.*np.pi  # convert to rad
    ha = lmst-ra
    sindec = np.sin(dec)
    sinlat = np.sin(lat)
    coslat = np.cos(lat)
    sinalt = sindec*sinlat+np.cos(dec)*coslat*np.cos(ha)
    sinalt = inrange(sinalt)
    alt = np.arcsin(sinalt)
    cosaz = (sindec-np.sin(alt)*sinlat)/(np.cos(alt)*coslat)
    cosaz = inrange(cosaz)
    az = np.arccos(cosaz)
    signflip = np.where(np.sin(ha) > 0)
    az[signflip] = 2.*np.pi-az[signflip]
    return alt, az