Date: Mon, 30 Oct 2000 10:18:23 -0700 (MST)
From: Bill Peters 
Subject: Manual weather parameters (KDATA:[SMT.DOC]MANUAL_WEATHER.DOC)
To: twilson, hbutner, paulg, bvila, mdumke

        Inputting Weather Data Manually			30 Oct 00

    The weather information is mainly used for the refraction calculation.
Refraction depends upon pressure, temperature, and humidity.  If the weather
station is broken, one can manually input values via OBSINP.  The OBSINP
command, REFR, controls whether the weather station data is used for refraction 
or the manual input from the observer is used.  REFR Y means use the weather
station, REFR N means use the values specified manually with the ATMP,
TEMP, and RELH commands.

    Normally, the humidity used for the refraction calculation is derived from
the 225 GHz opacity measured by the Tipper.  The OBSINP command, TIPR, controls
this.  TIPR Y means use Tau(225) while TIPR N means use the relative humidity
from the weather station (or from the RELH command).  To see the current
settings, use the OBSINP command, SHOW DP1. 

    If the weather station is broken, one should use the outside temperature
measured by one of the thermometers mounted on the building.  There is one
located on the balcony next to the air conditioning compressors on the third
floor.  Another is in the telescope chamber near the door to the control room. 
One can use the barometric pressure being reported for Safford by multiplying
the pressure in inches of mercury by the factor 23.37.  This converts a sea
level pressure in inches to a pressure in millibars at the altitude of the HHT.
(One can skip the relative humidity if the Tipper opacity is being used for
the humidity.)

    One should update these parameters regularly.  The complaint given once 
an hour on the ERROR log may remind you: "WEATHR DATA 2 OLD!".    
    
Summary:

    To see the weather values and the settings of TIPR and REFR, in OBST, type 

	OBSINP
	SHOW DP1

    To set for manual weather data, type

	REFR N

    To set the pressure to <millibar> and the temperature to <Celsius>, type

	ATMP <millibar>
	TEMP <Celsius>

    To return to weather station input, type

	REFR Y

    (To return to OBST, type QUIT)