final class DirectionOfMotion extends Object
By default, the spacecraft moves towards the North Celestial Pole (in the general direction of Polaris). This class allows you to change that default, and to see what the stars look like when the spacecraft is moving in a different direction.
For example, to point the spacecraft towards the galactic pole near the constellation of Leo, you can try (for J2000) the following values (in degrees):
DirectionRightAscension = 192.85 DirectionDeclination = +27.13 Phi = 33
To point the spacecraft towards the galactic center, you can try (for J2000):
DirectionRightAscension = 266.40 DirectionDeclination = -28.94 Phi = 30
The value for Phi is simply controls the rotation of the view about the direction of motion. You may adjust it to suit your taste.
Constructor and Description |
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DirectionOfMotion(double aDirectionRightAscension,
double aDirectionDeclination,
double aPhi)
Constructor.
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Modifier and Type | Method and Description |
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(package private) void |
changeCoordsOfThe(Star aStar)
Change the right ascension and declination of a
Star to reflect its coordinates with respect the
direction of motion of the spacecraft. |
(package private) boolean |
isNotDefault()
Return true only if the user has input at least one parameter that differs from the default.
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DirectionOfMotion(double aDirectionRightAscension, double aDirectionDeclination, double aPhi)
aDirectionRightAscension
- Right ascension of the direction of motion of the spacecraft, in radians.aDirectionDeclination
- Declination of the direction of motion of the spacecraft, in radians.aPhi
- Rotation angle about the direction of motion, in radians. Controls how the view is rotated.boolean isNotDefault()
void changeCoordsOfThe(Star aStar)
Star
to reflect its coordinates with respect the
direction of motion of the spacecraft. (Of course, the position of the star hasn't changed in space; this
is merely a convenient way of doing the calculation.)
In effect, the direction of motion of the spacecraft becomes the "new" North Celestial Pole.
This corresponds to a rotation of the coordinates.
(Implementation Note: this transformation is almost exactly the same as the transformation between equatorial coordinates and galactic coordinates.)
Starfield - Copyright Hirondelle Systems. Published March 1, 2014