Chronocalc
I wrote this script after I was busy updating my article on chronolocation, which can be found here.
It calculates the dates and times when the sun or moon is in a given position in the sky. It can be used during chronolocation tasks, to quickly find possible dates and times within a 15 minutes accuracy. For finding a more precise moment, one should use a tool like suncalc.org to find a closer match, or use the option --accurate.
Installation
Install all the requirements first:
pip install -r requirements.txt
Or with the newest versions:
python3.8 -m pip install -r requirements.txt
Usage
To determine the date and time, you need to have the following information already:
- The exact latitude and longitude of the location
- The year you want to calculate
- Height (altitude) of the sun or moon
- Direction (azimuth) of the sun or moon*
The script will pull the elevation information from an online source, and after this the script will iterate through a whole year, in 15 minute increments, and returns one of the following:
Sun
Two dates on either side of the solstice, where the given altitude and azimuth matches the closest to the calculated time. If it’s not possible to find a match, there might me two possibilities:
- The initial measurements are incorrect and the situation can’t exist
- The location is extrmely close to the equator, and the sun moves too fast for the 15 minute increment
If the latitude given is close to the equator, about 2 degrees or less off, you can use the --accurate option. This will change the calculation interval to 2 minutes, given a better chance to find a possible match. This will take longer to retrieve a result, but if there is a match, it should be shown.
Moon
To retrieve a list of dates where the moon is at a given position, use the optional argument --moon.
It will return all dates and times the moon is in the given position, and its illumination percentage. Since the moon can be in the same position multiple times a year, all dates that are within a are within a 2 degree limit of the altitude and azimuth are returned.
If there are no matches with the given parameter, it will return a message saying so. Change some variables, or check your findings, and run the script again. The --accurate argument has no use here.
Examples
To find the dates where the sun is in a given position:
python chronocalc.py -y 2020 -lat 50.9423 -lon 6.9579 -alt 32 -az 200
Result:
+---------------------------+----------+---------+
| Date and time | Altitude | Azimuth |
+---------------------------+----------+---------+
| 2020-03-08T14:00:00+01:00 | 32.08 | 202.87 |
| 2020-10-05T14:30:00+02:00 | 32.09 | 200.58 |
+---------------------------+----------+---------+
Find all the dates where the moon is at a given position in the sky:
python chronocalc.py -y 2018 -lat 50.9423 -lon 6.9579 -alt 30 -az 200 --moon
Result:
+---------------------------+----------+---------+--------------+
| Date and time | Altitude | Azimuth | Illumination |
+---------------------------+----------+---------+--------------+
| 2018-01-08T08:15:00+01:00 | 31.28 | 218.99 | 56.6% |
| 2018-01-22T19:15:00+01:00 | 28.95 | 221.78 | 28.0% |
| 2018-02-05T07:00:00+01:00 | 28.28 | 219.48 | 73.7% |
| 2018-03-04T04:45:00+01:00 | 30.69 | 219.79 | 94.1% |
| 2018-03-18T15:45:00+01:00 | 31.54 | 219.73 | 1.4% |
| 2018-04-14T14:45:00+02:00 | 28.95 | 220.78 | 2.9% |
| 2018-04-28T02:15:00+02:00 | 30.16 | 219.45 | 95.3% |
| 2018-05-12T13:15:00+02:00 | 31.91 | 220.0 | 11.5% |
| 2018-05-25T00:15:00+02:00 | 31.48 | 220.87 | 78.6% |
| 2018-06-08T11:15:00+02:00 | 28.91 | 221.16 | 34.2% |
| 2018-06-21T23:00:00+02:00 | 28.62 | 219.23 | 65.3% |
| 2018-07-18T21:00:00+02:00 | 29.86 | 220.99 | 39.3% |
| 2018-08-02T07:45:00+02:00 | 30.6 | 219.83 | 75.1% |
| 2018-08-29T05:45:00+02:00 | 29.26 | 219.47 | 93.1% |
| 2018-09-11T17:30:00+02:00 | 29.16 | 221.32 | 5.1% |
| 2018-09-26T04:30:00+02:00 | 31.86 | 221.75 | 98.8% |
| 2018-10-23T02:15:00+02:00 | 31.01 | 218.37 | 96.8% |
| 2018-11-05T13:00:00+01:00 | 28.59 | 221.58 | 5.8% |
| 2018-11-18T23:15:00+01:00 | 28.16 | 219.37 | 79.9% |
| 2018-12-02T10:45:00+01:00 | 31.51 | 219.53 | 24.7% |
| 2018-12-16T21:45:00+01:00 | 30.99 | 218.8 | 63.4% |
+---------------------------+----------+---------+--------------+
