NavList:

Frank wrote:

"The astronomical data underlying those tables originates from the numerical integrations generated by NASA/JPL. This is the same highly accurate data that is used to navigate spacecraft around the Solar System, and it is the same data that underlies the major official almanacs including the (real) Nautical Almanac and the Astronomical Almanac."

Speaking of the Nautical Almanac, I periodically check my spreadsheet against it to verify that I don't need to fix anything. A few days ago, I decided to do a random check. I set the time and date in my spreadsheet to 00:00:00 UT1, March 30th, 2025. Everything looked good until I got to Venus. My spreadsheet gives a GHA of 192°00.9', but the N.A. gives 192°00.5'. This is the largest discrepancy I have seen so far. Of course, my first thought was that my spreadsheet must be wrong. So, I opened several other programs to see what output they gave. MICA, AstroNav, Teacup Navigation, Frank's online almanac, Andrés' app ... hell, even ICE and StarPilot all agreed that the value should be 192°00.9'. The only source I've found so far that does agree with the N.A. is [unsurprisingly] the USNO website. I only bothered to check a few other hours after that, so I'm not sure when the apparent error starts or stops.

Anyway, am I crazy, or is the 2025 Nautical Almanac off by 0.4' when it comes to Venus' GHA?

Cheers!

Sean C.