How to use “sunset.exe”
This is a freeware software, by S. Volkan @ Z. Neda (2002)
(Babes-Bolyai University, Cluj, Romania, E-mail: [email protected] )
Feel free to use and distribute it!
The program visualizes a sunset scenario for different atmospheric conditions and
observational height. It runs under Windows environment (Windows 98 or newer).
It simulates the rim of the observed setting Sun (together with the un-refracted rim)
as it sets down.
The user can fix the atmospheric conditions, observational height, precision of the
calculation and the general properties of the troposphere and stratosphere in the
menu. The calculation for the rim of the sun is based on our study, which can be
downloaded from http://www.fi.uib.no/~neda/sunset/sunset.pdf (pdf version), or
http://www.fi.uib.no/~neda/sunset/sunset.ps (post-script version).
To use the program unpack the sunset.zip archive on your computer, and you will
get the executable: sunset.exe. Run the program under Windows environment.
The menu and picture from below will appear:
The window is scalable and movable after lowering it in the standard manner (by
clicking on the upper right corner the lowering button).
To view a sunset, one must first fix in the menu the atmospheric and observational
conditions and generate a dataset. Fixing new atmospheric conditions is not
necessary (one can use the predefined values), however generating the data used
for visualization is necessary!
A. Fixing the atmospheric conditions:
Some normal and frequently encountered parameters were already
predefined.
These parameters are summarized on the left part of the program window. If
you want to change them:
- click the menu-bar on the “Atmosphere”
- a window appears and you can choose either the “Temperature” or
“Parameters”
- selecting “Temperature” you will pointed in this version of the
program automatically the “Standard” temperature profile of the
atmosphere (the only option). In the menu-box that appears you can
fix the properties of the troposphere and stratosphere. For the
troposphere you can fix the temperature at a given height, the lapserate and the upper limit of the troposphere. . For the stratosphere one
can fix its upper limit.
- selecting “Parameters” one can fix the pressure at the observers
height, and the range of the wave-number for the visible light. This
range should not be modified, since we already inserted here the
visible domain.
After changing the parameters the new parameters are automatically updated
on the left side of the program window.
B. Generating the data
- click the menu-bar on “Generate”
- a window appears and you can choose either the “Inclination” or
“Method” boxes.
- selecting the “Method” you can fix the precision of the calculations for
the light-ray path. Better precision can be achieved by lowering the
light-path sequence and the inverse function error. Defining better
precision will increase the calculation time. The predefined values
yields good results in acceptable calculation time.
- selecting “Inclination” one can fix the wave-number for the light-rays
used in the calculations, the altitude of the observer, the highest
inclination angle from where the Sun’s rim is computed (this should
be positive), the number of points during which the refraction is
followed, and the number of data for the inverse function. Again, the
predefined values for the number of points in which the calculation is
done for the direct and inverse function yields good results in
relatively short computational time, and for general purposes one
should not change these. After fixing the desired parameters one
should click in this window the “generate” button to generate the data.
A crop of the calculation and its progress is plotted on a new visible
window.
C. Visualizing the sunset
- click the menu-bar on “Simulate”
- a window appears and you can choose either the “Monocromatic” or
“Visualization” boxes.
- Choose “Monocromatic” and the program begins to simulate the
Sunset for the fixed atmospheric conditions. The observed rim is
plotted with red. The momentary asymmetry ratio (flatness) of the rim
is written on the screen. The real (un-refracted) rim of the Sun is
plotted by white line. The simulation can be paused by doubleclicking inside the simulation window with the mouse. After the
simulation is paused, double-clicking in the window continues the
simulation.
- When the simulation is paused you can change the position on the
screen for the center-point of the optical horizon (the border-line
between the blue sky and brown land), or the magnification (the total
vertical inclination angle viewed) by selecting in the “Simulate” menu
the “Visualization” option. After the bottom of the Sun reaches the
horizon the flatness is not calculated anymore and the last asymmetryratio (valid for the last totally visible shape of the rim) remains printed
on the screen.
The program window, and the program can be closed by clicking on the upper right
corner of the window on the usual “close” [x] button.
Have fun!
Z. Neda & S.Volkan
April, 2002 Cluj, Romania