How can I get Sun altitude in the Java Script?

[Ivan Rubtsov]

Hi!
I am creating my own script for taking dark frames. I need to be sure the shooting is at dusk. How can I get the altitude of the sun in a java script? Or perhaps there are other ways to determine that the shooting o is at dusk?

[Bob Denny]

Assuming you have the ASCOM NOVAS COM Positional Astronomy engine, and Kepler Orbit Engine installed (API Docs Included), this should work for you, given the current full Julian Date "JD":

var KT = new ActiveXObject("Kepler.Ephemeris");
KT.BodyType = 0;                                            // Planet
KT.Number = 3;                                              // EARTH
var KA = KT.GetPositionAndVelocity(JD);
var tvec = new ActiveXObject("NOVAS.PositionVector")
tvec.x = -KA(0)                                             // Reverse Cartesian vector for Sun from Earth
tvec.y = -KA(1)
tvec.z = -KA(2)
var RA = tvec.RightAscension                                // J2000 Equatorial, convert to alt-az
var Dec = tvec.Declination

If you have ACP available you can use its CoordinateTransform to go from RA/Dec to Alt/Az.

[Ivan Rubtsov]

Thank you Bob! It works!

[Bob Denny]

You're welcome :-) :-)

[Ivan Rubtsov]

Does anybody know, how to calculate Moon Alt/Az?

[Bob Denny]

Hi Ivan -- This is a package I put together that permits "Moon" to be a target in an ACP Plan. It uses a modified version of Stephen Moshier's 'aa' program and ACP UserActions. Read the readme's in the zip file and also the info in ACP Help about UserActions.

[Ivan Rubtsov]

Thanks, Bob!