Programs to assist with photographing the August 21, 2017 total solar eclipse.
The two programs work out when totality, when the moon completely obstructs the sun, will occur for a location. This is done using data published by NASA that projects the irregular shape of the moon's umbra onto the irregular shape of the Earth at one second intervals. The programs should be able to tell when totality starts and ends to within one second. The NASA data is available at:
https://svs.gsfc.nasa.gov/4518
The umbra17_1s files are the important ones. The programs by default expect to find the files in a subdirectory of this project called "nasashapes".
The code here was written in a bit of a rush, so it isn't my best. I don't have a lot of time to test. It does seem to be working and useful, though.
The umbra_test program takes longitude and latitude values either from command-line arguments or from stdin. It evaluates if the location will see totality, and if it does, when it will start, when it will end, and the total duration. On a Raspberry Pi Zero for a location near the longest totality, it takes about 15 seconds to produce the answer, and under 8 seconds for additional nearby locations.
The umbra_lcd program is intended for use on a portable computer system built around a Raspberry Pi or something similar. It uses GPSD to find its current location, a HD44780 or compatible LCD to show the results, and a buzzer to provide audible notifications. It uses a 20x4 display and a rotary encoder with a button, although use of input is still limited. I also wrote it with the expectation that ntpd will be running and synchronizing the clock with GPS.
What the umbra_lcd program does not yet do that I'd like it to:
- Estimate the very beginning and ending of the eclipse (it does a somewhat stupid version of this based on where I'm planning to be)
- Show sun azimuth and elevation for the very beginning, ending, and mid-totality (it does this, but the data comes from Alt_Az_Table and is for where I'm planning to be)
Both programs need the following libraries:
- GDAL
- GEOS
The umbra_lcd program additionally needs these libraries:
If any of those last three libraries are not found, the umbra_lcd program will not be built.
The default location for the DUDS library is at the same directory level as wherever this code finds itself.