Advice Needed for an Art Project (Moon Tracking)

Hello everyone,

I'm an artist who's looking for advice on how to calculate the moon's
position for a piece of sculpture (for a temporary exhibition
primarily geared for children opening this coming April in the
Netherlands).

The idea of the piece is this: a life sized standing figure should be
constantly pointing at the moon's position -- 24 hours a day whether
it is above or below the horizon. The figure is to be driven by two
computer controlled motors, one to turn the figure to face the correct
direction (azimuth angle) and the other to raise and lower the
figure's arm to indicate the correct elevation.

What I'm looking for is either an existing program that can provide
these two coordinates to the software driving the motors (to drive the
motors I will be using Real Basic http://www.realbasic.com) or advice
on how such a program or script might be written. The program must run
on Mac OS X.

Please note I am an absolute neophyte when it comes to astronomy or
celestial mechanics. After playing around with some astronomy software
on my Mac I've understood the need to specify the observer's location
(geophysical coordinates) and, of course, the date. I had hoped that I
could mine the azimuth angle and altitude out of such an astronomy
program but now understand that the position of heavenly bodies is
calculated in RA and DEC (and have heard that conversion between the
RA and DEC and azimuth angle and altitude is complicated).

Is there an easy way for me to do what I want to do?

(Anyone want to collaborate?)

Any help or advice here would be greatly appreciated.

Kind regards,

-- Paul

Funambulist wrote:

Hello everyone,

I'm an artist who's looking for advice on how to calculate the moon's
position for a piece of sculpture (for a temporary exhibition
primarily geared for children opening this coming April in the
Netherlands).


Suggest something like XEphem for moon angular position given
place, date and time.

The idea of the piece is this: a life sized standing figure should be
constantly pointing at the moon's position -- 24 hours a day whether
it is above or below the horizon. The figure is to be driven by two
computer controlled motors, one to turn the figure to face the correct
direction (azimuth angle) and the other to raise and lower the
figure's arm to indicate the correct elevation.

You can work out the calculations from sources like

"Astronomical Algorithms" by Jean Meeus

"Explanatory Supplement To The Astronomical Almanac" Edited by
P. Kenneth Seidelmann, U.S. Naval Observatory, Washington D.C.


What I'm looking for is either an existing program that can provide
these two coordinates to the software driving the motors (to drive the
motors I will be using Real Basic http://www.realbasic.com) or advice
on how such a program or script might be written. The program must run
on Mac OS X.

XEphem runs on Mac OS X and sports telescope control


Please note I am an absolute neophyte when it comes to astronomy or
celestial mechanics. After playing around with some astronomy software
on my Mac I've understood the need to specify the observer's location
(geophysical coordinates) and, of course, the date. I had hoped that I
could mine the azimuth angle and altitude out of such an astronomy
program but now understand that the position of heavenly bodies is
calculated in RA and DEC (and have heard that conversion between the
RA and DEC and azimuth angle and altitude is complicated).

Is there an easy way for me to do what I want to do?

(Anyone want to collaborate?)

Any help or advice here would be greatly appreciated.

Kind regards,

-- Paul

Sam Wormley wrote in message ...

Suggest something like XEphem for moon angular position given
place, date and time.

Sam, thank you for pointing me to XEphem. I'm looking into it now --
though -- as it is X windows -- I wonder how easy it is to make the
azimuth angle and altitude to RealBasic and the USB interface that I'm
using?

You can work out the calculations from sources like
"Astronomical Algorithms" by Jean Meeus

"Explanatory Supplement To The Astronomical Almanac" Edited by
P. Kenneth Seidelmann, U.S. Naval Observatory, Washington D.C.

Thanks too for these pointers.

Since posting here I've stumbled across Keith Burnett's pages on
Astronomical Calculations

http://www.xylem.f2s.com/kepler/index.html

And wonder whether his 'Position of the Moon to 0.3 Degrees'
calculation and his 'Converting RA and DEC to ALT and AZ' might be all
I need?

http://www.xylem.f2s.com/kepler/moon.html
http://www.xylem.f2s.com/kepler/altaz.html

Has anyone any experience with these calculations? Anyone know how I
can contact Keith?

Thanks again,

-- Paul

"Funambulist" wrote in message
om...
Sam Wormley wrote in message
...

Suggest something like XEphem for moon angular position given
place, date and time.

Sam, thank you for pointing me to XEphem. I'm looking into it now --
though -- as it is X windows -- I wonder how easy it is to make the
azimuth angle and altitude to RealBasic and the USB interface that I'm
using?

You can work out the calculations from sources like
"Astronomical Algorithms" by Jean Meeus

"Explanatory Supplement To The Astronomical Almanac" Edited by
P. Kenneth Seidelmann, U.S. Naval Observatory, Washington D.C.

Thanks too for these pointers.

Since posting here I've stumbled across Keith Burnett's pages on
Astronomical Calculations

http://www.xylem.f2s.com/kepler/index.html

And wonder whether his 'Position of the Moon to 0.3 Degrees'
calculation and his 'Converting RA and DEC to ALT and AZ' might be all
I need?

http://www.xylem.f2s.com/kepler/moon.html
http://www.xylem.f2s.com/kepler/altaz.html

Has anyone any experience with these calculations? Anyone know how I
can contact Keith?

Thanks again,



No, but your tip of the index finger at arms length subtends an angle of a
degree or so (in my case about 1.5 degrees). In that case, an accuracy of
0.3 degrees would be more than adequate for your purposes.

DaveL