OBSWIND

Name

obswind

Purpose

Compute possible observing window for a celestial object.

Description

This routines determines the possible observing window for an object.
The times of sunrise and sunset are left as input parameters to help
speed up the computations. It is expected that this routine will be called
many times for a given date (LST0), but for different objects.
RTIME and STIME denote the earliest time and the latest time that the object
can be observed. Note that if RTIME > STIME then the range passes through
0 hours. RKIND and SKIND tell what limits the ends of the window as follows:
RKIND will be either 'sunset' or 'rises' for TYPE = 0
RKIND will be 'sunset' for TYPE = 1
RKIND is undefined for TYPE = -1
SKIND will be either 'sunrise' or 'sets' for TYPE = 0
SKIND will be 'sunrise' for TYPE = 1
SKIND is undefined for TYPE = -1
if TYPE = 2 then object is not available when sun is down.

Calling Sequence

obswind,lst0,lat,ra,dec,srise,sset,rtime,rkind,stime,skind,type

Inputs

lst0 - Local Sidereal Time at local midnight (radians).
lat - Latitude of observatory (radians).
ra - right ascension of object (radians), should be of date.
dec - declination of object (radans), should be of date.
srise - Time of sunrise (JD).
sset - Time of sunset (JD).

Optional Input Parameters

Keyword Input Parameters

AMLIMIT - Air Mass limit to denote rise and set of object. Default=3.0

Outputs

rtime - Time of opening of observing window (at rise or sunset)
rkind - String that identifies limit, either 'sunset' or 'rises'
stime - Time of closing of observing window (at rise or sunset)
skind - String that identifies limit, either 'sunset' or 'rises'
type - Indicator of type of window
2 - Object not available when sun is down.
1 - Object always up.
0 - Object rises and sets.
-1 - Object always down.

Keyword Output Parameters

Common Blocks

Side Effects

Restrictions

Procedure

Modification History

1997/9/3, Written by Marc W. Buie, Lowell Observatory
2002/03/27, MWB, fixed AMLIMIT bug.
2012/01/28, MWB, validation changed to enforce only scalar input