Observing bright variable star Algol

Algol, designated Beta Persei (β Persei, abbreviated Beta Per, β Per), known colloquially as the Demon Star, is a bright multiple star in the constellation of Perseus and one of the first non-nova variable stars to be discovered.

Algol is a three-star system, consisting of Beta Persei Aa1, Aa2, and Ab – in which the hot luminous primary β Persei Aa1 and the larger, but cooler and fainter, β Persei Aa2 regularly pass in front of each other, causing eclipses. Thus Algol’s magnitude is usually near-constant at 2.1, but regularly dips to 3.4 every 2.86 days during the roughly 10-hour-long partial eclipses. The secondary eclipse when the brighter primary star occults the fainter secondary is very shallow and can only be detected photoelectrically. See more about Algol at Wikipedia.

 

Create a go-lang program that creates a list of minima of the star Algol that occur during the night hours for a given period. The beginning and end of the period are entered from the command line in the format YYYY-MM-DD.

Minimum Epoch = ME  Sun Alt = SunA

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Algol (Beta Persei) Nighttime Minima Finder
Period: 2026-07-01 to 2026-12-31
Location: Lat 44.0000°, Lon -92.5000°
Maximum Sun Altitude: -6.0°
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[ 1] ME #3129 | 2026-07-03 05:52 UTC | 2026-07-03 00:52 CDT | SunA: -22.9°
[ 2] ME #3130 | 2026-07-06 02:41 UTC | 2026-07-05 21:41 CDT | SunA:  -7.4°
[ 3] ME #3136 | 2026-07-23 07:35 UTC | 2026-07-23 02:35 CDT | SunA: -23.5°
[ 4] ME #3137 | 2026-07-26 04:24 UTC | 2026-07-25 23:24 CDT | SunA: -21.6°
[ 5] ME #3143 | 2026-08-12 09:18 UTC | 2026-08-12 04:18 CDT | SunA: -17.8°
[ 6] ME #3144 | 2026-08-15 06:07 UTC | 2026-08-15 01:07 CDT | SunA: -31.9°
[ 7] ME #3145 | 2026-08-18 02:56 UTC | 2026-08-17 21:56 CDT | SunA: -17.3°
[ 8] ME #3150 | 2026-09-01 11:00 UTC | 2026-09-01 06:00 CDT | SunA:  -6.5°
[ 9] ME #3151 | 2026-09-04 07:49 UTC | 2026-09-04 02:49 CDT | SunA: -34.0°
[10] ME #3152 | 2026-09-07 04:38 UTC | 2026-09-06 23:38 CDT | SunA: -36.0°
[11] ME #3153 | 2026-09-10 01:27 UTC | 2026-09-09 20:27 CDT | SunA: -10.7°
[12] ME #3158 | 2026-09-24 09:32 UTC | 2026-09-24 04:32 CDT | SunA: -26.3°
[13] ME #3159 | 2026-09-27 06:21 UTC | 2026-09-27 01:21 CDT | SunA: -47.4°
[14] ME #3160 | 2026-09-30 03:10 UTC | 2026-09-29 22:10 CDT | SunA: -34.3°
[15] ME #3165 | 2026-10-14 11:14 UTC | 2026-10-14 06:14 CDT | SunA: -13.1°
[16] ME #3166 | 2026-10-17 08:03 UTC | 2026-10-17 03:03 CDT | SunA: -45.5°
[17] ME #3167 | 2026-10-20 04:52 UTC | 2026-10-19 23:52 CDT | SunA: -53.8°
[18] ME #3168 | 2026-10-23 01:41 UTC | 2026-10-22 20:41 CDT | SunA: -27.1°
[19] ME #3173 | 2026-11-06 09:46 UTC | 2026-11-06 03:46 CST | SunA: -33.8°
[20] ME #3174 | 2026-11-09 06:35 UTC | 2026-11-09 00:35 CST | SunA: -61.5°
[21] ME #3175 | 2026-11-12 03:24 UTC | 2026-11-11 21:24 CST | SunA: -49.0°
[22] ME #3176 | 2026-11-15 00:13 UTC | 2026-11-14 18:13 CST | SunA: -16.0°
[23] ME #3180 | 2026-11-26 11:29 UTC | 2026-11-26 05:29 CST | SunA: -19.3°
[24] ME #3181 | 2026-11-29 08:18 UTC | 2026-11-29 02:18 CST | SunA: -53.4°
[25] ME #3182 | 2026-12-02 05:07 UTC | 2026-12-01 23:07 CST | SunA: -65.5°
[26] ME #3183 | 2026-12-05 01:56 UTC | 2026-12-04 19:56 CST | SunA: -35.8°
[27] ME #3188 | 2026-12-19 10:00 UTC | 2026-12-19 04:00 CST | SunA: -38.4°
[28] ME #3189 | 2026-12-22 06:49 UTC | 2026-12-22 00:49 CST | SunA: -67.8°
[29] ME #3190 | 2026-12-25 03:38 UTC | 2026-12-24 21:38 CST | SunA: -52.9°
[30] ME #3191 | 2026-12-28 00:27 UTC | 2026-12-27 18:27 CST | SunA: -18.8°