### SLA_DE2H

$h,\delta$ to Az,El

ACTION:
Equatorial to horizon coordinates (double precision).
CALL:
CALL sla_DE2H (HA, DEC, PHI, AZ, EL)

##### RETURNED:
Azimuth is returned in the range $0\phantom{\rule{0.3em}{0ex}}-\phantom{\rule{0.3em}{0ex}}2\pi$; north is zero, and east is $+\pi /2$. Elevation is returned in the range $±\pi$.
In some applications it will be important to specify the correct type of hour angle and declination in order to produce the required type of azimuth and elevation. In particular, it may be important to distinguish between elevation as affected by refraction, which would require the observed $\left[\phantom{\rule{0.3em}{0ex}}h,\delta \phantom{\rule{0.3em}{0ex}}\right]$, and the elevation in vacuo, which would require the topocentric $\left[\phantom{\rule{0.3em}{0ex}}h,\delta \phantom{\rule{0.3em}{0ex}}\right]$. If the effects of diurnal aberration can be neglected, the apparent $\left[\phantom{\rule{0.3em}{0ex}}h,\delta \phantom{\rule{0.3em}{0ex}}\right]$ may be used instead of the topocentric $\left[\phantom{\rule{0.3em}{0ex}}h,\delta \phantom{\rule{0.3em}{0ex}}\right]$.