outfly/tools/generate_starchart.py

#!/usr/bin/env python
# This script requires the following file in the assets/tmp/ directory:
# https://github.com/astronexus/HYG-Database/blob/cbd21013d2bb89732b893be357a6f41836dbe614/hyg/CURRENT/hygdata_v41.csv

import csv
import sys
import math

#def entry(ra_hour, ra_min, ra_sec, dec_deg, dec_min, dec_sec, mag, name, color_index):
#    return [
#        ra_hour*15 + ra_min*0.25 + ra_sec*0.004166,
#        dec_deg + dec_min/60 + dec_sec/3600,
#        mag,
#        name,
#        color_index,
#    ]
#
#
#CUSTOM_ENTRIES = [
#    entry(0, 42, 44.3, 41, 16, 9, 3.44-15, 0.63, "Andromeda Galaxy"),
#]

# Lower apparent magnitude = brighter.
# Sun = -26.7
# Sirius = -1.44
# Betelgeuse = 0.45
# Polaris (north star) = 1.97
# Meissa (orion's head, 8th brightest star in orion) = 3.33
MAX_APPARENT_MAGNITUDE = 7.0

print("// The \"STARS\" was autogenerated by \"genrate_starchart.py\" using data")
print("// from the HYG database: https://github.com/astronexus/HYG-Database/tree/main/hyg")
print("// License: CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/")
print("")
print("pub const STARS: &[[f32; 5]] = &[")


def render(ra, dec, mag, ci, proper):
    # Takes ra/deg in degrees
    ra = float(ra)
    dec = float(dec)
    mag = float(mag)

    distance = 1.0
    ra_radians = math.radians(ra * 15)  # ra is in [0, 24], multiplying by 15 gives degrees in [0, 360]
    dec_radians = math.radians(dec)
    #print(f"ra_radians={ra_radians}, dec_radians={dec_radians}, dec={dec}, ra={ra}", file=sys.stderr)
    x = distance * math.cos(dec_radians) * math.cos(-ra_radians)
    y = distance * math.cos(dec_radians) * math.sin(-ra_radians)
    z = distance * math.sin(dec_radians)

    # Correct for differences in coordinate system axes
    x, y, z = x, z, y

    comment = f" // {proper}" if proper else ""

    brightness = 2.512 ** (0 - mag)

    print(f"    [{x:.04}, {y:.04}, {z:.04}, {brightness:.04}, {ci}],{comment}")


total = 0
count = 0
count_extra = 0
with open("assets/tmp/hygdata_v41.csv", "r", encoding="utf-8") as f:
    for entry in csv.DictReader(f):
        total += 1
        ra = entry['ra']
        dec = entry['dec']
        mag = entry['mag']
        ci = entry['ci']
        proper = entry['proper']
        proper = "".join([c for c in proper if c.isalnum() or c in ' -_'])
        if not all([ra, dec, mag, ci]):
            continue
        if float(mag) > MAX_APPARENT_MAGNITUDE:
            continue
        render(ra, dec, mag, ci, proper)
        count += 1
#for entry in CUSTOM_ENTRIES:
#    render(entry[0], entry[1], entry[2], entry[3], entry[4])
#    count_extra += 1

print("];")
print(f"Wrote {count} stars (total={total}) + {count_extra} extra entries.", file=sys.stderr)