astral.AstralError: Sun never reaches 6 degrees below the horizon, at this location.

[exfizik]

I started getting this error about a week ago (getting close to summer solistice I'm guessing) for a location that's fairly up north, but nowhere near the pole - lat,lon = 62.55,-129.52. I've traced it back to the following code:

    def _hour_angle(self, latitude, declination, depression): 
        # arg values: 62.54999923706055, 21.466634091977532, 96 
        latitude_rad = radians(latitude)
        declination_rad = radians(declination)
        depression_rad = radians(depression)

        n = cos(depression_rad)
        d = cos(latitude_rad) * cos(declination_rad)
        t = tan(latitude_rad) * tan(declination_rad)
        h = (n / d) - t   # h: -1.0006730127306969 <- out of range for acos

        HA = acos(h)    # Exception here. 
        return HA

I'm not sure how to handle this. Is astral not supposed to work in my case?

[matkoniecz]

fairly up north, but nowhere near the pole

Have you checked whatever it is enough toward north that "Sun never reaches 6 degrees below the horizon, at this location" is true?

[exfizik]

Sorry, not working on that project any more, can't follow up. You decide what to do with the issue.

[RichardSWheatley]

Did you check each step in the equation? The cos function is returning a negative value for depression_rad. Most calculators will not do that.

Try checking that out before continuing.

[RichardSWheatley]

@exfizik one thing to note is that when using python cosine, it does return negative values and you should check for that.

n = cos(depression_rad)

look at your example and remember that 1 - sqrt(1-pow(sin(depression_rad), 2))) is the same as cos(depression_rad). Not as cool looking but it might give you a better answer.