kopia lustrzana https://github.com/peterhinch/micropython-samples
astronomy: Add twilight support.
Peter Hinch
rodzic
8c587764da
commit
0062b0f9a1
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@ -24,13 +24,15 @@ event in a 24 hour period starting at midnight. The midnight datum is defined in
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local time. The start is a day specified as the current day plus an offset in
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days.
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A `moonphase` function is also provided enabling the moon phase to be determined
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It can also compute Civil, Nautical or Astronomical twilight times. A
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`moonphase` function is also provided enabling the moon phase to be determined
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for any date.
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Caveat. I am not an astronomer. If there are errors in the fundamental
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algorithms I am unlikely to be able to offer an opinion, still less a fix.
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The code is currently under development: the API may change.
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The code is currently under development but I don't anticipate breaking changes
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to the API.
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## 1.1 Applications
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@ -41,14 +43,18 @@ lunar clocks such as this one - the "lunartick":
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## 1.2 Licensing and acknowledgements
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The code was ported from C/C++ as presented in "Astronomy on the Personal
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Some code was ported from C/C++ as presented in "Astronomy on the Personal
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Computer" by Montenbruck and Pfleger, with mathematical improvements contributed
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by Marcus Mendenhall and Raul Kompaß. Raul Kompaß substantially improved the
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accuracy when using 32-bit floating point. The sourcecode exists in the book and
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also on an accompanying CD-R. The file `CDR_license.txt` contains a copy of the
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license file on the disk, which contains source, executable code, and databases.
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This module (obviously) only references the source. I am not a lawyer; I have no
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idea of the legal status of code translated from sourcecode in a published work.
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by Marcus Mendenhall and Raul Kompaß. I (Peter Hinch) performed the port and
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enabled support for timezones. Raul Kompaß substantially improved the accuracy
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when run on hardware with 32-bit floating point.
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The sourcecode exists in the book and also on an accompanying CD-R. The file
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`CDR_license.txt` contains a copy of the license file on the disk, which
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contains source, executable code, and databases. This module only references the
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source. I have not spotted any restrictions on use in the book. I am not a
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lawyer; I have no idea of the legal status of code based on sourcecode in a
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published work.
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## 1.3 Installation
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@ -112,9 +118,13 @@ Args (float):
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* `lat=LAT` Latitude in degrees (-ve is South). Defaults are my location. :)
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* `long=LONG` Longitude in degrees (-ve is West).
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* `lto=0` Local time offset in hours to UTC (-ve is West); the value is checked
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to ensure `-12 < lto < 12`. See [section 2.3](./README.md#23-effect-of-local-time).
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to ensure `-15 < lto < 15`. See [section 2.3](./README.md#23-effect-of-local-time).
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The constructor sets the object's date to the system date as defined by machine
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time (`MT`).
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* `tl=None` If provided, set an offset in degrees for the definition of twilight
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(6 is Civil, 12 is Nautical, 18 is Astronomical). By default twilight times are
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not computed, saving some processor time. Offsets are positive numbers
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representing degrees below the horizon where twilight is deemed to start and end.
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## 2.2 Methods
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@ -126,6 +136,8 @@ instance.
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* `sunset(variant: int = 0)`
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* `moonrise(variant: int = 0)`
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* `moonset(variant: int = 0)`
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* `tstart(variant: int = 0)` Twilight start
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* `tend(variant: int = 0)` Twilight end
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* `is_up(sun: bool)-> bool` Returns `True` if the selected object is above the
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horizon.
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* `has_risen(sun: bool)->bool` Returns `True` if the selected object has risen.
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@ -135,7 +147,7 @@ moon, 0.5 is full. See [section 3](./README.md#3-the-moonphase-function) for
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observations about this.
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* `set_lto(t)` Set local time offset `LTO` in hours relative to UTC. Primarily
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intended for daylight saving time. The value is checked to ensure
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`-12.0 < lto < 12.0`. See [section 2.3](./README.md#23-effect-of-local-time).
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`-15.0 < lto < 15.0`. See [section 2.3](./README.md#23-effect-of-local-time).
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The return value of the rise and set method is determined by the `variant` arg.
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In all cases rise and set events are identified which occur in the current 24
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@ -376,13 +388,16 @@ finally:
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A recalculation is triggered whenever the 24 hour local time window is changed,
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such as calling `.set_day()` where the stored date changes. Normally two days of
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data are calculated, except where the local time is UTC where only one day is
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required. The time to derive one day's data on RP2040 was 707μs.
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required. The time to derive one day's data on RP2040 was 707μs (no twilight
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calculation, standard clock).
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The accuracy of rise and set times was checked against online sources for
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several geographic locations. The online data had 1 minute resolution and the
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checked values corresponded with data computed on a platform with 64 bit
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floating point unit. The loss of precision from using a 32 bit FPU was no more
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than 30s.
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than 3s.
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For reasons which are unclear, the `is_up()` method is less precise, showing
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incorrect results when within a few minutes of the rise or set time.
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The lunar phase calculation is poor. It is adequate for displaying a phase icon
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or adjusting a pointer, but not good enough for predicting lunar quarters.
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I plan to improve this, but it may be via a separate module.
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@ -201,17 +201,17 @@ def minimoon(t):
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class RiSet:
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def __init__(self, lat=LAT, long=LONG, lto=0): # Local defaults
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def __init__(self, lat=LAT, long=LONG, lto=0, tl=None): # Local defaults
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self.sglat = sin(radians(lat))
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self.cglat = cos(radians(lat))
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self.long = long
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if not -12 < lto < 12:
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raise ValueError("Invalid local time offset.")
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self.check_lto(lto) # -15 < lto < 15
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self.lto = round(lto * 3600) # Localtime offset in secs
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self.tlight = sin(radians(tl)) if tl is not None else tl
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self.mjd = None # Current integer MJD
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# Times in integer secs from midnight on current day (in local time)
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# [sunrise, sunset, moonrise, moonset]
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self._times = [None] * 4
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# [sunrise, sunset, moonrise, moonset, cvend, cvstart]
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self._times = [None] * 6
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self.set_day() # Initialise to today's date
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# ***** API start *****
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@ -243,12 +243,17 @@ class RiSet:
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def moonset(self, variant: int = 0):
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return self._format(self._times[3], variant)
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def tend(self, variant: int = 0):
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return self._format(self._times[4], variant)
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def tstart(self, variant: int = 0):
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return self._format(self._times[5], variant)
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def moonphase(self) -> float:
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return self._phase
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def set_lto(self, t): # Update the offset from UTC
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if not -12 < t < 12: # No need to recalc beause date is unchanged
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raise ValueError("Invalid local time offset.")
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self.check_lto(t) # No need to recalc beause date is unchanged
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lto = round(t * 3600) # Localtime offset in secs
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def has_risen(self, sun: bool):
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@ -273,15 +278,20 @@ class RiSet:
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# ***** API end *****
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# Re-calculate rise and set times
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def update(self, mjd):
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self._times = [None] * 4
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self._times = [None] * 6
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days = (1, 2) if self.lto < 0 else (1,) if self.lto == 0 else (0, 1)
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tr = None # Assume no twilight calculations
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ts = None
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for day in days:
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self.mjd = mjd + day - 1
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sr, ss = self.rise_set(True) # Sun
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mr, ms = self.rise_set(False) # Moon
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sr, ss = self.rise_set(True, False) # Sun
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# Twilight: only calculate if required
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if self.tlight is not None:
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tr, ts = self.rise_set(True, True)
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mr, ms = self.rise_set(False, False) # Moon
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# Adjust for local time. Store in ._times if value is in 24-hour
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# local time window
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self.adjust((sr, ss, mr, ms), day)
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self.adjust((sr, ss, mr, ms, tr, ts), day)
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self.mjd = mjd
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def adjust(self, times, day):
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@ -305,6 +315,10 @@ class RiSet:
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mi, sec = divmod(tmp, 60)
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return f"{hr:02d}:{mi:02d}:{sec:02d}"
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def check_lto(self, t):
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if not -15 < t < 15:
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raise ValueError("Invalid local time offset.")
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# See https://github.com/orgs/micropython/discussions/13075
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def lstt(self, t, h):
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# Takes the mjd and the longitude (west negative) and then returns
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@ -333,10 +347,13 @@ class RiSet:
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# Modified to find sunrise and sunset only, not twilight events.
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# Calculate rise and set times of sun or moon for the current MJD. Times are
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# relative to that 24 hour period.
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def rise_set(self, sun):
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def rise_set(self, sun, tl):
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t_rise = None # Rise and set times in secs from midnight
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t_set = None
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sinho = sin(radians(-0.833)) if sun else sin(radians(8 / 60))
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if tl:
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sinho = -self.tlight
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else:
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sinho = sin(radians(-0.833)) if sun else sin(radians(8 / 60))
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# moonrise taken as centre of moon at +8 arcmin
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# sunset upper limb simple refraction
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# The loop finds the sin(alt) for sets of three consecutive
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