°
Go back to Red Rock Energy.moshier
Astronomy and numerical software source codes by Stephen L. Moshier. aa-55.zip Self contained Ephemeris Calculator.
analemma
The Analemma is the key to astronomical and solar tracking mathematics.
ayiomamitis
Strange as it may seem, only seven times has someone ever managed to successfully image the solar analemma as a multi-exposure on a single piece of film. Anthony's are very beautiful.
greatcircle
Great Circle Studio's Solar Calculator.
Jean Meeus' great book on astronomical calculations.
How to calculate alt/az of sun for any time/location - Do It Yourself.
Accurate to about 1/10th of a degree.
How to calculate alt/az of sun for any time/location - Easier Way.
schlyter
Computing planetary positions - a tutorial with worked examples.
By Paul Schlyter, Stockholm, Sweden
Pages From A Dialist's Notebook.
An Indoor Analemma
Chart of the Equation of Time
digi
A digital sundial
Richard D. Swensen's Sundial at the University of Wisconsin River Falls.
NOAA Surface Radiation Research Branch Solar Position Calculator
Definitions of Astronomical Terms.
solar.bas By Michael A. Syczylo
checksun
checkSun.
Spectrum
Galileo/GPS controlled Solar Tracking
Freeware/GPL context
The Quick Almanac.
This FTP: site has a lot of good software to download.
susdesign
Sustainable By Design
provides a suite of shareware design tools on sustainable energy topics including solar position and path diagrams.
pathfinder
The Solar Pathfinder.
Sun chart program. Generates sun path diagrams in PDF format.
nrel
Solar Position Algorithm for Solar Radiation Applications
NREL has published this document to help designers of solar concentrator develop software to track the sun in high resolution.
I have arranged the order of these books with the most desirable at the top.
Astronomy With Your Personal Computer
by Peter Duffett-Smith
Edition Desc: 2nd ed
Published 1990
ISBN 0 521 38093 6 hardback $74.95
ISBN 0 521 38995 X Paperback $30.95
Get the out of print book here.
The software in this book is based written in Microsoft's GW Basic. The equations are very extensive.
BTW you want the second edition because it has more routines than the 1st.
I would recommend obtaining a copy of this book before all others. His method of presenting the equations and the resultant programs is masterful. One can take his programs and easily modify them for special uses. This book is required reading for those who are writing astronomical software. Even if you are writing low accuracy algorithms, such as for solar tracking, his programs will give you a benchmark to compare the results.
Download the software from here.
This is a self extracting compressed file. Put it in a separate directory and run it.
Astronomical Formulae for Calculators
by Jean H. Meeus
Edition Desc: 4th ed
Published 1988
ISBN 0 943 39622 0 Paperback $22.75
Get the out of print book here.
If I had no other books, this is the one to have. Meeus is recognized as the authority on astronomical calculations. Others always refer to him for reference.
Practical Astronomy with Your Calculator
by Peter Duffett-Smith
Edition Desc: 3rd ed
Published 1988
ISBN 0 521 35629 6 hardback $54.95us
Get the out of print book here.
The third edition of a guide book for amateur astronomers features new sections on generalized coordinate transformations, nutations, aberration, and selenographic coordinates as well as improvements to the sunrise and moonrise calculations.
Easy PC Astronomy
by Peter Duffett-Smith
Edition Desc: book & disk
Published 1996
ISBN 0 521 56052 7 Paperback $30.95
Get the book here.
Easy PC Astronomy is the book for all those who want to make astronomical calculations easily and accurately. A simple but powerful script language called AstroScript is provided on a disk with the book, ready to use on any IBM PC-type computer.
I don't have this book myself, but it sounds good.
heavensabove
Welcome to Heavens-Above.
If you're interested in satellites or astronomy, you've come to the right place! Our aim is to provide you with all the information you need to observe satellites such as the International Space Station and the Space Shuttle, spectacular events such as the dazzlingly bright flares from Iridium satellites as well as a wealth of other spaceflight and astronomical information.
bartels
Computer Operated Telescopes
By Mel Bartels
solpos
Solar Position and Intensity
NREL's SOLPOS 2.0
Source code written in "C"
burnett
Position of the Sun
By Keith Burnett
Accurate to about 1/40th of a degree.
refraction
I have placed a version of Keith's program that corrects for atmospheric refraction along with Stephen Moshier's program into a .zip file. In addition there are some handling programs to compare the results. Unzip into a separate directory. Read the ReadMe.txt file for instructions.
'*********************************************************
' This program will calculate the position of the Sun
' using a low precision method found on page C24 of the
' 1996 Astronomical Almanac.
'
' The method is good to 0.01 degrees in the sky over the
' period 1950 to 2050.
'
' QBASIC program by Keith Burnett (kburnett@geocity.com)
'
' Work in double precision and define some constants
'
DEFDBL A-Z
pr1$ = "\ \#####.##"
pr2$ = "\ \#####.#####"
pr3$ = "\ \#####.###"
pi = 4 * ATN(1)
tpi = 2 * pi
twopi = tpi
degs = 180 / pi
rads = pi / 180
'
' Get the days to J2000
' h is UT in decimal hours
' FNday only works between 1901 to 2099 - see Meeus chapter 7
'
DEF FNday (y,m,d,h) = 367 * y - 7 * (y + (m + 9) \ 12) \ 4 + 275 * m\ 9 + d - 730531.5 + h / 24
'
' define some arc cos and arc sin functions and
' a modified inverse tangent function
'
DEF FNacos (x)
s = SQR(1 - x * x)
FNacos = ATN(s / x)
END DEF
DEF FNasin (x)
c = SQR(1 - x * x)
FNasin = ATN(x / c)
END DEF
'
' the atn2 function below returns an angle in the
' range 0 to two pidepending on the signs of x and y.
'
DEF FNatn2 (y, x)
a = ATN(y / x)
IF x < 0 THEN a = a + pi
IF (y < 0) AND (x > 0) THEN a = a + tpi
FNatn2 = a
END DEF
'
' the function below returns the true integer part,
' even for negative numbers
'
DEF FNipart (x) = SGN(x) * INT(ABS(x))
'
' the function below returns an angle in the range
' 0 to two pi
'
DEF FNrange (x)
b = x / tpi
a = tpi * (b - FNipart(b))
IF a < 0 THEN a = tpi + a
FNrange = a
END DEF
'
' Find the ecliptic longitude of the Sun
'
DEF FNsun (d)
'
' mean longitude of the Sun
'
L = FNrange(280.461 * rads + .9856474# * rads * d)
'
' mean anomaly of the Sun
'
g = FNrange(357.528 * rads + .9856003# * rads * d)
'
' Ecliptic longitude of the Sun
'
FNsun = FNrange(L + 1.915 * rads * SIN(g) + .02 * rads * SIN(2 * g))
'
' Ecliptic latitude is assumed to be zero by definition
'
END DEF
'
'
'
CLS
'
' get the date and time from the user
'
' INPUT " year : ", y
' INPUT " month : ", m
' INPUT " day : ", day
' INPUT "hour UT : ", h
' INPUT " minute : ", mins
' INPUT " lat : ", glat
' INPUT " long : ", glong
y = 2002
m = 7
day = 9
h = 0
mins = 23
glat = 45.08096
glong = -93.02377
glat = glat * rads
glong = glong * rads
h = h + mins / 60
d = FNday(y, m, day, h)
'
' Use FNsun to find the ecliptic longitude of the
' Sun
'
lambda = FNsun(d)
'
' Obliquity of the ecliptic
'
obliq = 23.439 * rads - .0000004# * rads * d
'
' Find the RA and DEC of the Sun
'
alpha = FNatn2(COS(obliq) * SIN(lambda), COS(lambda))
delta = FNasin(SIN(obliq) * SIN(lambda))
'
' Find the Earth - Sun distance
'
r = 1.00014 - .01671 * COS(g) - .00014 * COS(2 * g)
'
' Find the Equation of Time
'
equation = (L - alpha) * degs * 4
'
' find the Alt and Az of the Sun for a given position
' on Earth
'
' hour angle of Sun
LMST = FNrange((280.46061837# + 360.98564736629# * d) * rads + glong)
hasun = FNrange(LMST - alpha)
'
' conversion from hour angle and dec to Alt Az
sinalt = SIN(delta) * SIN(glat) + COS(delta) * COS(glat) * COS(hasun)
altsun = FNasin(sinalt)
y = -COS(delta) * COS(glat) * SIN(hasun)
x = SIN(delta) - SIN(glat) * sinalt
azsun = FNatn2(y, x)
'
' print results in decimal form
'
PRINT
PRINT "Position of Sun"
PRINT "==============="
PRINT
PRINT USING pr2$; " days : "; d
PRINT USING pr1$; "longitude : "; lambda * degs
PRINT USING pr3$; " RA : "; alpha * degs / 15
PRINT USING pr1$; " DEC : "; delta * degs
PRINT USING pr2$; " distance : "; r
PRINT USING pr1$; " eq time : "; equation
PRINT USING pr1$; " LST : "; FNrange(LMST) * degs
PRINT USING pr1$; " azimuth : "; azsun * degs
PRINT USING pr1$; " altitude : "; altsun * degs
END
'*********************************************************
Below is the output from the old program when run for
11:00 UT on 1997 August 7.
year : 2002
month : 8
day : 7
hour UT : 11
minute : 0
Position of Sun
===============
days : -877.04167
longitude : 134.98
RA : 9.163
DEC : 16.34
distance : 1.01408
eq time : -5.75
Below is the output from the program including Altitude and Azimuth
in Chicago, run for 15:00 UT on 2001 March 4th (09:00h Chicago time),
compared with the altitude and azimuth calculated from
Chris Marriott's SkyMap Pro 6 demo.
year : 2001
month : 3
day : 4
hour UT : 15
minute : 30
lat : 41.87
long : -87.64
Position of Sun
===============
days : 428.14583
longitude : 344.13
RA : 23.025
DEC : -6.24
distance : 0.99173
eq time : -11.68
azimuth : 134.56
altitude : 30.68
Skymap 6
--------
Right ascension: 23h 1m 29.93s = 23.025
Declination: -6° 14' 58.0" = -6.249
Altitude: 30° 42' 20" = 30.706
Azimuth: 134° 33' 41" = 134.561
The errors here are about 1.5 arcmin for altitude and much less for
Azimuth. Errors are higher than for the RA and Dec and this may be
due to the failure to allow for the TDT-UT time difference in the
method given here. To put this all in perspective, the Sun moves
about 0.25 of a degree in the sky between 0900 and 0901 that morning!