SunFN, version 1.2 for Russ Webb's RPN (Shareware)
and SunFN, version 1.3 REGISTERED Version
Copyright (c) 1997 by Marvin E. Wilborne III

Overview
--------

This function set extension to Russ Webb's RPN calculator (seperately
available shareware from http://kale.ee.cornell.edu/pilot/) computes the
Sun rise and set times for a location for any date.

The shareware version should work for most locations correctly except areas
where the sun doesn't rise or set for more than a day (the poles ring a
bell).  

Polar locations are supported and button help and additional buttons for
checking the current Lon, Lat and UTC settings are available in the registered 
version.

Operation
---------

Before using the function set, you need to enter your longitude (east is
negative) and your latitude (south is negative) in Degrees Minutes Seconds
format (i.e. ddd.mmss).

To enter the Longitude for Danville VA which is 79 degrees 24 minutes West,
enter "79.24" and press the "lon" function button.

To enter the Latitude for Danville VA, which is 36 degrees 34 minutes North,
enter "36.34" and press the "lat" function button.

The answer that is returned is in UT, unless you put a value in UTC which is
the offset for your area or time zone.  For Danville VA that is currently
-4.00 on 9-28-1997.

Once you have the lon, lat and utc set, you're ready to get the sun rise and
set times for the location.

Enter the date in mm.ddyyyy format, for example, Sunday September 9, 1997
should be entered as 9.281997.  Press "When" function button to get the
sun rise (second entry on stack) and sun set (top of stack) in hh.mmss format
(hours minutes seconds).  NOTE:  Your RPN calculator must be in DEGREE mode
for these functions to work.

The display will show:

7.103246                the sun rise time, 7:10:32 am
19.054495               the sun set time, 7:05:44 pm

I tested the program against an example on page 56 of the "Practical
Astronomy with Your Calculator" book by Peter Duffet-Smith.  His results
for sun rise and sun set on July 27, 1978 at 0 degrees longitude and 52
degrees North latitude are:  4h 18m 47s (GMT) and 19h 49m 52s (GMT),

SunFN returns:  4h 13m 49s and 19h 59m 05s.  SunFN takes into account the
upper limb and apparent size of the Sun where the calculations by Duffet-Smith
work for the center of the Sun.

Button Definitions
==================
lon     - set the longitude
lat     - set the latitude
utc     - set the UTC offset

?lon    - what is the longitude         (registered version only)
?lat    - what is the latitude          (registered version only)
?utc    - what is the UTC offset        (registered version only)

Version 1.2, Last row of buttons:

When    - When does the sun rise and set
Tdy     - put today on the stack
?       - Tell me about SunFN

Registered Version 1.3, Last row of buttons:

W       - When does the sun rise and set for the date on the stack.
T       - put today on the stack
X       - Select a day in the future, 1 to 5 days and compute Sun rise and
          Sun set (you don't have to press W).  Real nice for getting the
          times for tomorrow!
?       - Tell me about SunFN

Registration
============

This function set is Shareware.  You can download it and use it for 30 days
without registering.  If you continue to use it after 30 days, please
register by sending $5.00 to:

        Marvin E. Wilborne III
        124 Matthew Circle
        Danville, VA 24540

Or you can register on-line at PilotGear's Shopping Mall:
        http://www2.viaweb.com/pilotgearsw/

Or you can call PilotGear at 800-741-9070.

If you've already registered a RPN function set that I've developed, then
you're already registered for these.  I call it cross registering.

Address comments or questions by e-mail to:

        wilborne@gamewood.net


Release Notes
-------------
28 October 1997         Updated the documentation for the registered version
                        1.3 of SunFN.  Cool new button for selecting future
                        dates for easier operation.

21 October 1997         Updated the documentation.  Updated the registered
                        version of the Sun Functions so that now each button
                        has help on it (using the RPN help lookup function)
                        and 3 additional buttons have been added to allow
                        checking the current value of Lon, Lat and UTC.

2 October 1997          Added "tdy" button to shareware version, removed
                        7 use reminder to register screen and put in a 21 use
                        expiration.

29 September 1997       Registered version 1.1 release, has a "today" button
                        abbreviated "tdy" that puts the current date on the
                        stack.
                             
28 September 1997       Initial release of version 1.0 functions.

Legal Notice
============
This software is copyrighted (c) 1997 by Marvin E. Wilborne III. Furthermore,
I make  no warranty with respect to the quality of this software, nor do I
warrant that its operation will be error-free. The author claims no liability
for data loss or any other problems caused directly or indirectly by use of
this application.

This function set may be freely distributed provided that this file is
included with the PDB file that contains the functions.
