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.
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One option is an article at Sky and Telescope SkyAndTelescope.org/stargazing-and-observing/the-minima-of-algol/ . One can enter a date in the format mm/dd/yyyy and calculate generate a table with eight rows and two columns. The first column has time and date in Universal time, second colon in local time.
For example:
07/24/2026 @ 01:41 UT = 07/23/2026 @ 08:41 pm
08/13/2026 @ 03:21 UT = 08/12/2026 @ 10:21 pm
It would be nice to verify that local time is really CDT.
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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.
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Minimum Epoch = ME Sun Alt = SunA
========================================================= 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° ========================================================= [ 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°
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