in reply to Trouble with time zones and Sun rise/set

For even more precision, you should check if the Astro:: modules use UTC (Coordinated universal time) or TAI (international atomic time). UTC includes leap seconds, TAI doesn't (which is why TAI is prefered for space related stuff like astronomy and orbital parameters).

Currently, the offset UTC-TAI = -37s, but you should regularly (January and July) check against the International Earth Rotation and Reference Systems (IERS) Bulletin C for any upcoming leap second changes.

37 seconds doesn't sound like much, but when you use a big telescope, it can mean the difference between getting a nice picture of the crab nebula or getting a picture of something else that is up to 0.15 degrees (9 arcminutes?) away from the center of the crab nebula, if my math is correct.

perl -e 'use Crypt::Digest::SHA256 qw[sha256_hex]; print substr(sha256_hex("the Answer To Life, The Universe And Everything"), 6, 2), "\n";'

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Re^2: Trouble with time zones and Sun rise/set
by GrandFather (Saint) on Apr 22, 2022 at 00:53 UTC

    The Astro::Coords modules use UTC. For my current project I'm just interested in providing a report for naked eye and maybe binocular observers so the TAI/UTC disparity doesn't matter. The software I use for pointing telescopes does know about such things, but I don't have to worry about it. Much more important is to remember that the software's default epoch is JNow which is almost never correct and that I have to bludgeon it into using J2000 to get things pointed correctly!

    Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond
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