Python implementation of NOAA's Solar Position Calculators

NOAA has the calculation details at their website at Solar Calculation Details

pysunNOAA is based on the spreadsheet NOAA_Solar_Calculations_day.xls . All the calculation cells in row 2 of the spreadsheet are implemented in pysunNOAA. This is a work in progress. But it is fully usable at this point

Here is what it can do:

import datetime
from pysunnoaa import noaa

latitude = 40 # Latitude (+ to N)
longitude = -105 # Longitude (+ to E)
timezone = -6 # Time Zone (+ to E)
thedatetime = datetime.datetime(2010, 6, 21, 9, 54)

altitude, azimuth = noaa.sunposition(
latitude, longitude, timezone, thedatetime, atm_corr=True
)

print(f"{altitude=}, {azimuth=}")

>> altitude=47.36178497432497, azimuth=98.30691558695895

The above calculation is corrected for atmospheric diffraction. We can also do the calculation without the correction for atmospheric diffraction by setting atm_corr=False:

altitude, azimuth = noaa.sunposition(
    latitude, longitude, timezone, thedatetime, atm_corr=False
)
print(f"{altitude=}, {azimuth=}")

>> altitude=47.346932081680364, azimuth=98.30691558695895

Let us take a look at generating multiple sun positions for a time series. First we have to generate the time series:

thedates = noaa.datetimerange(
    datetime.datetime(2024, 6, 21, 10), # start
    datetime.datetime(2024, 6, 21, 11), # stop
    minutes=10 # step
) # The arguments are similar to python's range.
  # It returns a generator
for thedate in thedates:
    print(thedate)

2024-06-21 10:00:00
2024-06-21 10:10:00
2024-06-21 10:20:00
2024-06-21 10:30:00
2024-06-21 10:40:00
2024-06-21 10:50:00

So let us generate the sun positions for this time series:

thedates = noaa.datetimerange(
    datetime.datetime(2024, 6, 21, 10),
    datetime.datetime(2024, 6, 21, 11),
    minutes=10
)

positions = noaa.sunpositions(latitude, longitude, timezone, thedates, atm_corr=False)
for altitude, azimuth in positions:
    print(f"{altitude=}, {azimuth=}")

altitude=48.44972994443188, azimuth=99.43756106034147
altitude=50.33276597510335, azimuth=101.44934328356527
altitude=52.20206053830976, azimuth=103.57347468902549
altitude=54.05415607848319, azimuth=105.82830623146941
altitude=55.88497413825557, azimuth=108.23537482765607
altitude=57.689656999063025, azimuth=110.82001062044083

Let us print this again:

for altitude, azimuth in positions:
    print(f"{altitude=}, {azimuth=}")

WHAT !!! Why did it not print anything ??

Both noaa.datetimerange and noaa.sunpositions are generators. Once you loop through the generator, the values are exhausted (or emptied). To get the values again you will need to call the functions again:

thedates = noaa.datetimerange(
    datetime.datetime(2024, 6, 21, 10),
    datetime.datetime(2024, 6, 21, 11),
    minutes=10
)

positions = noaa.sunpositions(latitude, longitude, timezone, thedates, atm_corr=False)
for altitude, azimuth in positions:
    print(f"{altitude=}, {azimuth=}")

altitude=48.44972994443188, azimuth=99.43756106034147
altitude=50.33276597510335, azimuth=101.44934328356527
altitude=52.20206053830976, azimuth=103.57347468902549
altitude=54.05415607848319, azimuth=105.82830623146941
altitude=55.88497413825557, azimuth=108.23537482765607
altitude=57.689656999063025, azimuth=110.82001062044083

Another useful thing is to be able to calculate sunset and sunrise. Here we go:

sunrise = noaa.sunrise(40, -105, -6, datetime.datetime(2010, 6, 21))
sunset = noaa.sunset(40, -105, -6, datetime.datetime(2010, 6, 21))
print(f"{sunrise=}")
print(f"{sunset=}")

>> sunrise=datetime.datetime(2010, 6, 21, 5, 31, 15, 842680)
>> sunset=datetime.datetime(2010, 6, 21, 20, 32, 8, 805539)

That's all for now.