How do you multiply a GMT time (for example, 13:19) with a duration time (like 10 seconds.)
The examples I gave are the exact problem I need to do, btw. It's for an astrology thing... so how do I do that?
2007-07-24 19:05:52 · 3 answers · asked by Kiki 3 in Science & Mathematics ➔ Mathematics
Huh... in response to gjmb... I'm not actually sure.
I'm making up for the difference between 24-hour time and sidereal time. The sidereal day is less than 24 hours. Four minutes less. So each hour passes ten seconds faster. So I need to multiply the GMT time by ten seconds and subtract it from the GMT time to find my actual GMT time, astronomically speaking.
2007-07-24 19:27:00 · update #1
If you are trying to convert between GMT and sidereal time, I can't believe its for astrology. Astrologers are about 3000 years off when it comes to precession of the equinoxes. So far that they even have some wrong constellations in the zodiac. So a few minutes certainly won't matter to them. I'm assuming this is for astronomy.
The conversion is a little more complex than just 4 minutes per day. Jean Meeus' book "Astronomical Algorithms" gives an excellent treatment of this. In short, the sidereal time at Greenwich is:
ST = 280.46061837 + 360.98564736629 N + 0.000387933 T^2 - (T^3) / 38710000
This is in degrees, divide by 15 to get it in hours.
The parameter N is days since 0 hr, 1/1/2000 GMT. N need not be a whole number. For example, if your GMT is 06:00 on 1/15/200 then N=14.25. The parameter T is: T = N/36525.
If you do any amount of this sort of calculation, do yourself a favor and buy Meeus' book. Meeus' is the authority on this.
Again though, if this IS for astrology, use any number you like for sidereal time. Astrology is such a complete load of crap that I would find it offensive that someone would use the intelligence and elegance of Meeus and his formulae for that.
2007-07-28 10:24:56 · answer #1 · answered by Pretzels 5 · 0⤊ 0⤋
The whole piracy movement in the Gulf of Aden is ridiculous. These unarmed ships passing through this major water thoroughfare are completely vulnerable to attacks. It is out of control I believe that the identification of this vessel as American was a mistake. I believe it is actually Italian.
2016-05-17 23:06:08 · answer #2 · answered by ? 3 · 0⤊ 0⤋
are you sure that this 10 seconds is a duration and not an angle ?
update:
here is an example dont know if its usefull.
http://www.astrologicallyspeaking.com/calculate.htm
calculator for siderealtime
http://tycho.usno.navy.mil/sidereal.html
and ofcourse you dont need to calculate this by hand
http://alabe.com/freechart/
2007-07-24 19:24:04 · answer #3 · answered by gjmb1960 7 · 0⤊ 0⤋