Re: [pysolar-discuss] Strange azimuth values

[Jay Doscher <jay@xxxxxxxxxxxxx>]

I'm building a portable PV tracker. It's not done, but it usually posts to
Twitter every 3 hours as @SolarRobot7.  I am running pysolar 0.6 with
Python 2.7.

Thanks,
Jay

On Mon, May 11, 2015 at 8:13 AM, Brandon Stafford <brandon@xxxxxxxxxxxxxxx>
wrote:

> Hi Jay,
>
> That's a beautiful pair of charts! Is that a PV tracker you're building or
> what?
>
> One other question: what version of Pysolar are you needing to make
> azimuth corrections with?
>
> Brandon
>
> On Mon, May 11, 2015 at 10:48 AM, Jay Doscher <jay@xxxxxxxxxxxxx> wrote:
> > Looks like two curves to me, here's a graph of heading (corrected
> azimuth)
> > and elevation of my project.  Negative solar altitude simply means the
> sun
> > is below the horizon.
> >
> > On Mon, May 11, 2015 at 4:41 AM, Frank Lazzarini <flazzarini@xxxxxxxxx>
> > wrote:
> >>
> >> When I apply the proposed method I get these results,
> >>
> >> [2015-05-10 00:00:00+00:25] Altitude: -22.817917957170042 Azimuth:
> >> 0.9195853796406368
> >> [2015-05-10 01:00:00+00:25] Altitude: -21.35437669913535 Azimuth:
> >> 16.282490410169657
> >> [2015-05-10 02:00:00+00:25] Altitude: -17.460113361911073 Azimuth:
> >> 30.88264446553194
> >> [2015-05-10 03:00:00+00:25] Altitude: -11.530293822218377 Azimuth:
> >> 44.334853539473784
> >> [2015-05-10 04:00:00+00:25] Altitude: -4.041985922217601 Azimuth:
> >> 56.64229429837951
> >> [2015-05-10 05:00:00+00:25] Altitude: 4.721075310609919 Azimuth:
> >> 68.08448558243651
> >> [2015-05-10 06:00:00+00:25] Altitude: 13.916416678430616 Azimuth:
> >> 79.1019578849806
> >> [2015-05-10 07:00:00+00:25] Altitude: 23.540263468364685 Azimuth:
> >> 90.25884449955726
> >> [2015-05-10 08:00:00+00:25] Altitude: 33.162952138663265 Azimuth:
> >> 102.29127881328759
> >> [2015-05-10 09:00:00+00:25] Altitude: 42.311459924908625 Azimuth:
> >> 116.22795411782772
> >> [2015-05-10 10:00:00+00:25] Altitude: 50.279286820496274 Azimuth:
> >> 133.49311577994877
> >> [2015-05-10 11:00:00+00:25] Altitude: 55.94436234658116 Azimuth:
> >> 155.49523632286264
> >> [2015-05-10 12:00:00+00:25] Altitude: 57.89747249155467 Azimuth:
> >> 181.6026287381771
> >> [2015-05-10 13:00:00+00:25] Altitude: 55.45948436540424 Azimuth:
> >> 207.40278382169132
> >> [2015-05-10 14:00:00+00:25] Altitude: 49.46294168127422 Azimuth:
> >> 228.8272461199938
> >> [2015-05-10 15:00:00+00:25] Altitude: 41.31880137304067 Azimuth:
> >> 245.63086306581897
> >> [2015-05-10 16:00:00+00:25] Altitude: 32.09659468953159 Azimuth:
> >> 259.28835550065156
> >> [2015-05-10 17:00:00+00:25] Altitude: 22.46665426651643 Azimuth:
> >> 271.18090530087704
> >> [2015-05-10 18:00:00+00:25] Altitude: 12.887187896956561 Azimuth:
> >> 282.29565250233105
> >> [2015-05-10 19:00:00+00:25] Altitude: 3.8032148272317357 Azimuth:
> >> 293.34291810798067
> >> [2015-05-10 20:00:00+00:25] Altitude: -4.854352153303335 Azimuth:
> >> 304.8696257443884
> >> [2015-05-10 21:00:00+00:25] Altitude: -12.152382809733522 Azimuth:
> >> 317.2976741424302
> >> [2015-05-10 22:00:00+00:25] Altitude: -17.83265833925366 Azimuth:
> >> 330.87639859009437
> >>
> >> On Sun, May 10, 2015 at 11:28 PM, Jay Doscher <jay@xxxxxxxxxxxxx>
> wrote:
> >>>
> >>> I found the same issue, and managed to successfully offset it in my
> >>> python code.  A disclaimer though- this works for me in the southwest
> US,
> >>> and may be different elsewhere.
> >>>
> >>> def getsolarheading():
> >>>         Azimuth = Pysolar.GetAzimuth(maplat, maplon,
> >>> datetime.datetime.utcnow())
> >>>         if Azimuth < 0:
> >>>                 if (Azimuth >= -180):
> >>>                         solarheading = ((Azimuth * -1) + 180)
> >>>                 if (Azimuth < -180):
> >>>                         solarheading = ((Azimuth * -1) - 180)
> >>>         if Azimuth >= 0:
> >>>                 solarheading = Azimuth
> >>>         return solarheading
> >>>
> >>> This code will translate the Azimuth from Pysolar into a compass
> heading.
> >>> I'm not sure what to tell you about altitude.
> >>>
> >>> Cheers,
> >>> Jay
> >>>
> >>> On Sun, May 10, 2015 at 2:05 PM, Frank Lazzarini <flazzarini@xxxxxxxxx
> >
> >>> wrote:
> >>>>
> >>>> Hi there,
> >>>>
> >>>> when I run the following simulation I get really odd azimuth values.
> >>>> Well at least they seem odd, if I understood the documentation
> correctly
> >>>> they from ~90 over 0 to -90 degrees. When I run a simulation of an
> entire
> >>>> day I get really odd values for azimuth.
> >>>>
> >>>> from pysolar.solar import get_azimuth, get_altitude
> >>>> from datetime import datetime
> >>>> from pytz import timezone
> >>>>
> >>>>
> >>>> latitude = 49.707524
> >>>> longitude = 6.244362
> >>>> year = 2015
> >>>> month = 5
> >>>> day = 10
> >>>>
> >>>>
> >>>> def get_sun_position(latitude, longitude, time):
> >>>>     alt = get_altitude(latitude, longitude, time)
> >>>>     azi = get_azimuth(latitude, longitude, time)
> >>>>     return alt, azi
> >>>>
> >>>> tzinfo = timezone('Europe/Luxembourg')
> >>>> today = datetime.now(tz=tzinfo)
> >>>>
> >>>> for hour in range(0, 23):
> >>>>     time = datetime(
> >>>>         year,
> >>>>         month,
> >>>>         day,
> >>>>         hour,
> >>>>         0,
> >>>>         tzinfo=tzinfo
> >>>>     )
> >>>>     alt, azi = get_sun_position(latitude, longitude, time)
> >>>>     print("[{}] Altitude: {} Azimuth: {}".format(time, alt, azi))
> >>>>
> >>>>
> >>>> Now when I run this I get the following values
> >>>>
> >>>>
> >>>> [2015-05-10 00:00:00+00:25] Altitude: -22.817917957170042 Azimuth:
> >>>> -180.91958537964064
> >>>> [2015-05-10 01:00:00+00:25] Altitude: -21.35437669913535 Azimuth:
> >>>> -196.28249041016966
> >>>> [2015-05-10 02:00:00+00:25] Altitude: -17.460113361911073 Azimuth:
> >>>> -210.88264446553194
> >>>> [2015-05-10 03:00:00+00:25] Altitude: -11.530293822218377 Azimuth:
> >>>> -224.33485353947378
> >>>> [2015-05-10 04:00:00+00:25] Altitude: -4.041985922217601 Azimuth:
> >>>> -236.6422942983795
> >>>> [2015-05-10 05:00:00+00:25] Altitude: 4.721075310609919 Azimuth:
> >>>> -248.0844855824365
> >>>> [2015-05-10 06:00:00+00:25] Altitude: 13.916416678430616 Azimuth:
> >>>> -259.1019578849806
> >>>> [2015-05-10 07:00:00+00:25] Altitude: 23.540263468364685 Azimuth:
> >>>> -270.25884449955726
> >>>> [2015-05-10 08:00:00+00:25] Altitude: 33.162952138663265 Azimuth:
> >>>> -282.2912788132876
> >>>> [2015-05-10 09:00:00+00:25] Altitude: 42.311459924908625 Azimuth:
> >>>> -296.2279541178277
> >>>> [2015-05-10 10:00:00+00:25] Altitude: 50.279286820496274 Azimuth:
> >>>> -313.49311577994877
> >>>> [2015-05-10 11:00:00+00:25] Altitude: 55.94436234658116 Azimuth:
> >>>> -335.49523632286264
> >>>> [2015-05-10 12:00:00+00:25] Altitude: 57.89747249155467 Azimuth:
> >>>> -1.6026287381770885
> >>>> [2015-05-10 13:00:00+00:25] Altitude: 55.45948436540424 Azimuth:
> >>>> -27.402783821691315
> >>>> [2015-05-10 14:00:00+00:25] Altitude: 49.46294168127422 Azimuth:
> >>>> -48.82724611999379
> >>>> [2015-05-10 15:00:00+00:25] Altitude: 41.31880137304067 Azimuth:
> >>>> -65.63086306581897
> >>>> [2015-05-10 16:00:00+00:25] Altitude: 32.09659468953159 Azimuth:
> >>>> -79.28835550065156
> >>>> [2015-05-10 17:00:00+00:25] Altitude: 22.46665426651643 Azimuth:
> >>>> -91.18090530087704
> >>>> [2015-05-10 18:00:00+00:25] Altitude: 12.887187896956561 Azimuth:
> >>>> -102.29565250233105
> >>>> [2015-05-10 19:00:00+00:25] Altitude: 3.8032148272317357 Azimuth:
> >>>> -113.34291810798067
> >>>> [2015-05-10 20:00:00+00:25] Altitude: -4.854352153303335 Azimuth:
> >>>> -124.86962574438837
> >>>> [2015-05-10 21:00:00+00:25] Altitude: -12.152382809733522 Azimuth:
> >>>> -137.2976741424302
> >>>> [2015-05-10 22:00:00+00:25] Altitude: -17.83265833925366 Azimuth:
> >>>> -150.87639859009437
> >>>>
> >>>>
> >>>>
> >>>> Any ideas?
> >>>>
> >>>> --
> >>>>
> >>>> Frank Lazzarini
> >>>> Email: flazzarini@xxxxxxxxx  Phone: +352 621 314 430
> >>>> Blog:   http://www.gefoo.org   LinkedIn:
> >>>> http://www.linkedin.com/pub/frank-lazzarini/1a/a30/112
> >>>>
> >>>
> >>
> >>
> >>
> >> --
> >>
> >> Frank Lazzarini
> >> Email: flazzarini@xxxxxxxxx  Phone: +352 621 314 430
> >> Blog:   http://www.gefoo.org   LinkedIn:
> >> http://www.linkedin.com/pub/frank-lazzarini/1a/a30/112
> >>
> >
>
>
>
> --
> Brandon Stafford
> Rascal Micro: small computers for art and science
> Somerville, MA, USA
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