Subpoint sun on earth

[powersoft]

I have read the documentation, in front of that I made a definition in python/skyfield to calculate the sublat position of the sun on earth. My question is the definition correct, have no clou how to check the results.
Thanks for any help.
Cheers Jan

`def subpoint_sun(time):
earth, sun = eph['earth'], eph['sun']

astr = earth.at(time).observe(sun)
ra, dec, distance = astr.apparent().radec()
earth = 399  # NAIF code for the Earth center of mass
ra_hours = ra.hours
dec_degrees = dec.degrees
zon = position_of_radec(ra_hours, dec_degrees, t=time, center=earth)
subpoint = wgs84.subpoint(zon)
return subpoint.latitude.degrees, subpoint.longitude.degrees

[brandon-rhodes]

Happily, a quick Google search brings back a number of pages that identify the subsolar point. For example:

https://www.timeanddate.com/worldclock/sunearth.php

Try checking your result against that.

Also, I think you can stop with the apparent() call and use that raw position to ask for a latitude and longitude:

https://rhodesmill.org/skyfield/earth-satellites.html#satellite-longitude-latitude-and-height

That would let you skip the step of generating an RA and dec. Good luck, and let us know what you find out!

[powersoft]

I have try this code, the first part is working, but the converting to the subpoint will not work. Please can you help me out with this.
`
from skyfield.api import load, wgs84
ts = load.timescale()
eph = load('de421.bsp')
sun, moon, earth = eph['sun'], eph['moon'], eph['earth']
utc_time = ts.now()

geocentric = moon.at(utc_time)
print(geocentric.position.au)
subpoint=wgs84.subpoint(geocentric)
`

[brandon-rhodes]

If you will try doing a print() of your moon.at(utc_time) result, you will see that it is not a geocentric position. Try what you did earlier: ask the earth at() a given time to observe() the Moon.

[powersoft]

Thanks for this, it is now simple. And the code is nice streamed

[brandon-rhodes]

Thanks for checking back in, I'm glad it works now!