# [AstroPy] Rotating and Transforming Vectors--Flight Path of a Celestial Body

Wayne Watson sierra_mtnview@sbcglobal....
Thu Dec 17 19:33:52 CST 2009

```I'm just getting used to the math and numpy library, and have begun
working on a problem of the following sort.

Two observing stations are equidistant, 1/2 degree, on either side of a
line of longitude of 90 deg west, and both are at 45 deg latitude. Given
the earth's circumference as 25020 miles, a meteor is 60 miles above the
point between the two sites. That is, if you were standing at long
90deg  and lat 45 deg, the meteor would be that high above you. 70 miles
along the long line is 1 degree, so the stations are 70 miles apart.  I
want to know the az and el of the meteor from each station.  With some
geometry and trig, I've managed to get that first point; however,  I can
see  moving the meteor say, 1/2 deg, along its circular path towards the
north pole is going to require more pen and pencil work to get the az/el
for it.

Long ago in a faraway time, I used to do this stuff. It should be easy
to rotate the vector to the first point 1/2 deg northward, and find the
vector there, then compute the new az and el from each station. Maybe.
I'm just beginning to look at the matrix and vector facilities in numpy.
Maybe someone can comment on how this should be done, and steer me
towards what I need to know in numpy.

--

(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site:  39° 15' 7" N, 121° 2' 32" W, 2700 feet

"... humans'innate skills with numbers isn't much
better than that of rats and dolphins."
-- Stanislas Dehaene, neurosurgeon

Web Page: <www.speckledwithstars.net/>

```