[time-nuts] Calculating sidereal time

Didier Juges shalimr9 at gmail.com
Sat Jan 19 03:04:52 UTC 2019


Hi Mark, Brooke,

Thanks for the offer, I did not know you had that option but I should not
be surprised :)
I believe there must be a rounding issue. I fixed an earlier issue that had
me way off (West longitude is NEGATIVE...)
I am now about 57 seconds off (late), which is an odd number, but is
constant, at least for the last hour or so that I have been scratching my
head about that.
I use double precision in the new code (the sidereal portion), it is an
add-on to the old 8051 code which was limited to 32 bit variables, float or
int, but the old code was working fine and was all integer. The relatively
small and constant offset is puzzling. I think I am going to stop for
tonight and wait to see if it's still 57 seconds tomorrow.
In the mean time, I'll look at your code. Thank you

Didier


On Fri, Jan 18, 2019 at 8:06 PM Mark Sims <holrum at hotmail.com> wrote:

> Check out the sidereal code in Lady Heather (it's in heathmsc.cpp) and see
> if anything looks usable.  Heather uses double precision floating point for
> all the time functions.  To display sidereal times set the time zone to
> GMST, GMAT, LMST, or LAST.
>
> Also, if you are doing integer arithmetic, check very carefully for
> overflows, etc.
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