set=# - calculates next Universal time when the sun's altitude is # degrees above the horizon as it is setting.
ut=hh:mm:ss - uses the universal time specified instead of right now.
date=dd/mm/yyyy - uses the universal date specified instead of today.
noelev - disables the correction of the time of setting for the effects of refraction, the fact that the sun has finite diameter and for the elevation of the observatory (taken from the telescope server).