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rise/transit/set times calculation #140

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@valeriy-sokoloff

Hi! I'm trying to compute the Moon and Sun rise, transit, and set times for a given date and location: example-riseset.c

$ ./example-riseset -0.833 SUN
'SUN' observed from lon = -73.920, lat = 40.730:
 will rise above  -0.8 degrees at  : 2025-08-20T10:16:48.868Z
 will transit at                   : 2025-08-20T17:04:33.411Z
 will set below  -0.8 degrees at   : 2025-08-20T23:51:36.179Z
$ ./example-riseset -0.833 MOON
'MOON' observed from lon = -73.920, lat = 40.730:
 will rise above  -0.8 degrees at  : 2025-08-20T06:58:31.859Z
 will transit at                   : 2025-08-20T14:56:18.920Z
 will set below  -0.8 degrees at   : 2025-08-20T22:43:35.827Z

At first glance, the results look good. However, when I compared them with data from USNO and imcee.fr - used as "sources of trust" - I noticed a discrepancy:

example usno imcee
sun rise 10:16:48 10:11 10:12
sun transit 17:04:33 16:59 16:59
sun set 23:51:36 23:46 23:45
moon rise 06:58:31 06:53 06:55
moon transit 14:56:18 14:51 14:51
moon set 22:43:35 22:38 22:37

The produced output appears to be about 5 minutes later than USNO/imcee.

I also tested different locations and dates, with and without built-in refraction calculations, using custom refraction calculations, and with dynamic elevation angle calculations. The discrepancy remains, up to +7 minutes.

It seems like there might be an underlying bug in supernovas.
Could you please check and confirm this, or let me know if I’m just missing something?

SuperNOVAS v.1.3.0-rc4
CSPICE V.N0067

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