Hi Brooke,
SV position in circular orbit repeats at 12h sidereal, but ground relative
az/el repeats at 24h sidereal. This is because of the earth 24h rotation rate.
After 12h your earth position will be 180deg away from (inertil) start position.
—
Björn
Sent from my iPhone
> On 21 Jan
Hi Didier:
I'm still very much interested. The main reason is the GPS satellites come
close to following the same ground track.
So I'd expect the elevation and azimuth to a given SVN to be the same on a 12
sidereal hour basis.
--
Have Fun,
Brooke Clarke
https://www.PRC68.com
On Sat 2019-01-19T12:15:28-0800 Steve Allen hath writ:
> The most expedient place to find them are roughly pages B7 to B12 in a
> current Astronomical Almanac. See for example
> https://babel.hathitrust.org/cgi/pt?id=uc1.31822038913307;view=1up;seq=116
Emphasizing one point, it has always been
Replying to my own email as I understand my mistake...
Of course the leap seconds must be applied. The whole point of the leap
seconds is for UTC to be consistent with the actual position of the earth
in the sky, so to get accurate mjd, I have to use UTC.
On Sat, Jan 19, 2019 at 11:33 AM Didier
On Fri, Jan 18, 2019 at 11:00 PM Steve Allen wrote:
>
> This expression is no longer in use. It was superseded Capitaine et al.
>
> http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003A%26A...406.1135C
> in which formalism it is explicitly disavowed that earth rotation is time.
>
>
Hi Steve,
Thanks a lot for the references and background information. Looks like I
have more reading to do... I was not planning to for this project but it is
interesting.
I have seen references to using half days in some code samples. I suppose
this is what Brooke referred to when he said
When I was playing with the sidereal time code I found lots of buggy/bogus
implementations and also lots of web calculators that were either totally wrong
or off by some amount.Same for sunrise/sunset code and equation-of-time
code. It's hard to know what code / sites you can trust.
On Fri 2019-01-18T15:18:08-0600 Didier Juges hath writ:
> //---
> // Craig Haley 20/09/01
> // 30-06-04 CSH made small changes
> // 05-01-05 CSH modified to use mjd rather than converting to jd
> // Didier Juges
> // 18Jan19
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,
Trying to add sidereal time to my Thunderbolt monitor (I am working on a
new design with an ARM Cortex chip so that I can have double precision
math), I am obviously not understanding something in the process as my
calculations are off.
Here what I am doing:
I have the GPS date which I convert to
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