kopia lustrzana https://github.com/peterhinch/micropython-samples
astronomy: Improve docs.
Peter Hinch
rodzic
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@ -47,6 +47,7 @@ Please also see the [official examples](https://github.com/micropython/micropyth
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4.15 [Date](./README.md#415-date) Small and simple classes for handling dates.
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4.16 [Greatest common divisor](./README.md#416-greatest-common-divisor) Neat algorithm.
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4.17 [2D array indexing](./README.md#417-2d-array-indexing) Use `[1:3, 20]` syntax to address a 2D array.
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4.18 [Astronomy](./README.md#418-astronomy) Derive Sun and Moon rise and set times, moon phase.
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5. [Module Index](./README.md#5-module-index) Supported code. Device drivers, GUI's, utilities.
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5.1 [uasyncio](./README.md#51-uasyncio) Tutorial and drivers for asynchronous coding.
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5.2 [Memory Device Drivers](./README.md#52-memory-device-drivers) Drivers for nonvolatile memory devices.
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@ -304,7 +305,7 @@ functions. See [the docs](./QUATERNIONS.md).
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## 4.13 A pyboard power meter
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This uses a Pyboard to measure the power consumption of mains powered devices.
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This uses a Pyboard to measure the power consumption of mains powered devices.
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Unlike simple commercial devices it performs a true vector (phasor) measurement
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enabling it to provide information on power factor and to work with devices
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which generate as well as consume power. It uses the official LCD160CR display
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@ -384,6 +385,12 @@ See [the docs](./parse2d/README.md).
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##### [Index](./README.md#0-index)
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## 4.18 Astronomy
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This module enables Sun and Moon rise and set times to be determined for timing
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applications or for lunar clocks. Moon phase can also be accessed. Designed to
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work at global locations and timezones. See [./astronomy/README.md].
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# 5. Module index
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This index references applications and device drivers that I have developed, in
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@ -1,5 +1,20 @@
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# Astronomical calculations in MicroPython
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1. [Overview](./README.md#1-overview)
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1.1 [Applications](./README.md#11-applications)
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1.2 [Licensing and acknowledgements](./README.md#12-licensing-and-acknowledgements)
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1.3 [Installation](./README.md#13-installation)
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2. [The RiSet class](./README.md#2-the-riset-class)
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2.1 [Constructor](./README.md#21-constructor)
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2.2 [Methods](./README.md#22-methods)
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3. [The moonphase function](./README.md#3-the-moonphase-function)
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4. [Utility functions](./README.md#4-utility-functions)
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5. [Demo script](./README.md#5-demo-script)
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6. [Scheduling events](./README.md#6-scheduling-events)
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7. [Performance and accuracy](./README.md#7-performance-and-accuracy)
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# 1. Overview
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This module enables sun and moon rise and set times to be determined at any
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geographical location. Times are in seconds from midnight and refer to any
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event in a 24 hour period starting at midnight. The midnight datum is defined in
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@ -14,14 +29,14 @@ 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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## Applications
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## 1.1 Applications
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There are two application areas. Firstly timing of events relative to sun or
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moon rise and set times, discussed later in this doc. Secondly constructing
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lunar clocks such as this one - the "lunartick":
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## Licensing and acknowledgements
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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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Computer" by Montenbruck and Pfleger, with mathematical improvements contributed
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@ -31,7 +46,7 @@ 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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## Installation
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## 1.3 Installation
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Installation copies files from the `astronomy` directory to a directory
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`\lib\sched` on the target. This is for optional use with the
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@ -60,35 +75,43 @@ After installation the `RiSet` class may be accessed with
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from sched.sun_moon import RiSet
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```
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# The RiSet class
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# 2. The RiSet class
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This holds the local geographic coordinates and the localtime offset relative to
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UTC. It is initialised to the current date and can provide the times of rise and
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set events occurring within a 24 hour window starting at 00:00:00 local time.
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The `RiSet` instance's date may be changed allowing rise and set times to be
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retrieved for other 24 hour windows.
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retrieved for other 24 hour windows. In continuously running applications which
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must access current rise and set times the application should re-calculate (by
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issuing `.set_day()`) prior to retrieving that day's data.
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Rise and set times may be retrieved in various formats including seconds from
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local midnight: this may be used to enable the timing of actions relative to a
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rise or set event.
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## Constructor
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## 2.1 Constructor
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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).
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Methods:
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* `set_day(day: int = 0)` `day` is the offset in days from the current system
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date. If `day` is changed compared to the object's currently stored value its
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rise and set times are updated. Returns the `RiSet` instance.
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## 2.2 Methods
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* `set_day(day: int = 0)` `day` is an offset in days from the current system
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date. The number of days from the specified day to a fixed epoch is calculated
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and compared to that stored in the instance. If there is a change the new value
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is stored and the rise and set times are updated - otherwise return is
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"immediate". Returns the `RiSet` instance.
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* `sunrise(variant: int = 0)` See below for details and the `variant` arg.
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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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* `is_up(sun: bool)` Returns `True` if the selected object is above the horizon.
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This calls `.set_day()` to ensure the current day is selected.
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* `moonphase()` Return current phase as a float: 0.0 <= result < 1.0. 0.0 is new
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moon, 0.5 is full.
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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 localtime offset in hours relative to UTC. Primarily intended
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for daylight saving time. Rise and set times are updated if the lto is changed.
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@ -110,13 +133,10 @@ r = RiSet(lat=47.609722, long=-122.3306, lto=-8) # Seattle 47°36′35″N 122
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r = RiSet(lat=-33.87667, long=151.21, lto=11) # Sydney 33°52′04″S 151°12′36″E
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```
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# The moonphase function
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# 3. The moonphase function
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This is a simple function whose provenance is uncertain. I have a lunar clock
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which uses the original C code. This has run for 14 years without issue, but I
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can't vouch for its absolute accuracy over long time intervals. The Montenbruck
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and Pfleger version is very much more involved but they claim accuracy over
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centuries.
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This is a simple function whose provenance is uncertain. It appears to produce
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valid results but I plan to implement a better solution.
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Args:
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* `year: int` 4-digit year
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@ -127,14 +147,14 @@ Args:
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Return value:
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A float in range 0.0 <= result < 1.0, 0 being new moon, 0.5 being full moon.
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# Utility functions
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# 4. Utility functions
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`now_days() -> int` Returns the current time as days since the platform epoch.
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`abs_to_rel_days(days: int) -> int` Takes a number of days since the Unix epoch
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(1970,1,1) and returns a number of days relative to the current date. Platform
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independent. This facilitates testing with pre-determined target dates.
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# Demo script
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# 5. Demo script
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This produces output for the fixed date 4th Dec 2023 at three geographical
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locations. It can therefore be run on platforms where the system time is wrong.
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@ -175,36 +195,36 @@ Moon rise 03:56:44 set 13:46:27
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Day: 6
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Sun rise 08:12:01 set 15:49:56
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Moon rise 05:18:32 set 14:00:11
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Maximum error 0. Expect 0 on 64-bit platform, 30s on 32-bit
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>>>
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```
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Code comments show times retrieved from `timeanddate.com`.
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# Scheduling events
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# 6. Scheduling events
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A likely use case is to enable events to be timed relative to sunrise and set.
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In simple cases this can be done with `asyncio`.
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In simple cases this can be done with `asyncio`. This routine, called before
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sunrise, will perform some action at dawn and quit:
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```python
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from sched.sun_moon import RiSet
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import time
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rs = RiSet()
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tsecs = time.time() # Time now in secs since epoch
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tsecs -= tsecs % 86400 # Last midnight in secs since epoch
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tmidnight = tsecs
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async def do_sunrise():
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while True:
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toff = time.time() - tmidnight # Seconds relative to midnight
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if toff > 0: # Midnight has passed, wait for sunrise
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twait = rs.sunrise() - toff # Assumes a latitude where sun must rise
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else: # Wait for tomorrow
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twait = tmidnight + 86400 + toff
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async def wait_for_sunrise():
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tsecs = time.time() % 86400 # Time now in secs since midnight
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rs.set_day() # Ensure today's date
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twait = rs.sunrise() - tsecs # Time before Sunrise
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if twait > 0: # Sunrise has not yet occurred
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await asyncio.sleep(twait)
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if toff > 0:
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# Turn the lights off, or whatever
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# Turn the lights off, or whatever
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```
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An alternative, particularly suited to more complex cases, is to use the
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The problem with the above is ensuring that `wait_for_sunrise` is called shortly
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after midnight. A simple solution is to use the
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[schedule module](https://github.com/peterhinch/micropython-async/blob/master/v3/docs/SCHEDULE.md).
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This allows more intuitive coding without the epoch calculations. The following
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is a minimal example:
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This may be installed with
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```bash
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$ mpremote mip install "github:peterhinch/micropython-async/v3/as_drivers/sched"
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```
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The following is a minimal example:
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```python
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import uasyncio as asyncio
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from sched.sched import schedule
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@ -249,3 +269,19 @@ try:
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finally:
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_ = asyncio.new_event_loop()
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```
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# 7. Performance and accuracy
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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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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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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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@ -248,6 +248,13 @@ class RiSet:
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self.lto = lto
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self.update(self.mjd)
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def is_up(self, sun: bool): # Return current state of sun or moon
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t = time.time() + self.lto # UTC
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t %= 86400
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t /= 3600 # UTC Hour of day
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self.set_day() # Ensure today's date
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return self.sin_alt(t, sun) > 0
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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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