Astrocraft

The positions of these planets in the sky are calculated from their orbital parameters (fully configurable), while also taking into account earth's own orbit. These include:

• Semi-Major Axis
• Orbital period
• Eccentricity
• Inclination
• Obliquity / Axial Tilt (For moons of planets)
• Precession

The brightness or size of a planet is calculated using:

• Absolute Magnitude (H)
• Distance to Earth / Observing Planet
• Distance to the Sun
• Phase Angle (Different phase curve models are used for different planets)

Satellites of planets (including The Moon) or even the Sun use the same algorithm. When the angular diameter of a planet exceeds a certain size, the mod switches from star-like rendering to vanilla-moon-like rendering.

Using a spyglass allows you to see stars, planets, asteroids or moons that are too faint to see with the naked eye. In some cases, large planets can be rendered with a texture, some showing phases like the moon (this is the case with Venus).

Below is a table of the major planets (except Earth), with descriptions of their in-game appearances:

Over 100 asteroids have also been added. These appear almost indistinguishable from dim stars, but subsequent observations may show their movements.

Moons

Both Jupiter and Saturn have easily observable moons. In a spyglass, they look like stars around the planet. You can see moons move over a single night, as they have short orbital periods. Moons disappear as they go behind the planet. You can also see the moons of Mars, but only when Mars is very close.

Positions in the Sky

Unlike in vanilla minecraft, where the sun, moon and stars pass overhead, they will now be tilted by the latitude set in the configuration (30°N by default). Additionally, the sun's path is also affected by its declination which changes throughout the year cycle (365 ingame days by default). This makes it similar to real life, where the sun only passes overhead in the tropics. Disable the 'Angled Sky' setting in the config for vanilla behavior.

Throughout the year, the sun moves relative to the stars, travelling through the zodiac. This determines which stars can be seen at a given time.

The Moon

The moon's position relative to the sun will depend on the moon's phase. At full moon, the moon stays opposite the sun, just like in vanilla minecraft. However, during a crescent phase, the moon will appear just to the left or right of the sun, and can be seen during the day. This mod also adds moonlight, which lights up the night around the full moon.

Changing Day / Night Lengths

Times of sunrise / sunset are also affected by the sun's declination (longer days around the summer solstice, shorter around the winter solstice). Setting latitude to 90° or -90° in the configuration will simulate polar day / night that are experienced at the poles.

Eclipses

This mod adds rare astronomical events such as eclipses. A lunar eclipse occurs when a full moon coincides with the moon crossing the ecliptic. The moon turns red and moonlight dims for a few minutes. During a new moon, the moon can partially or fully cover the sun, blocking out the sunlight and dimming the sky. Other astronomical objects, such as Mercury and Venus can also eclipse the sun, appearing similarly to sun spots.

Astrocraft makes the sun and moon the same size, so eclipses work properly. However it does not make them smaller like in real life.

Here you can toggle stars or planets off, disable star color, add your own stars and much more. The main option affecting performance is "Magnitude Limit", reduce this if you need to, or you want to simulate the appearance of an urban night sky.

Default "Year Length" is 365.25 minecraft days, this affects the orbital period of every planet / moon. This can be reduced if 365.25 days is too slow for you. Set to 100 days to retain the vanilla 8 day moon cycle.

Multiplayer Compatibility

Positions of planets and stars are calculated from the world time, therefore other players with Astrocraft installed playing on the same world will see the same stars and planets in the same position as you. However, this won't be the case if you change certain settings, such as "year length" or most settings in the "Planets" category.

Overlays and Constellations

Astrocraft can help you see the constellations by drawing them as lines in the sky. Enable the "Show Constellations" option under the "Overlays" category. It will now show you which stars make up each constellation. There are also options for other overlays such as a grid or the ecliptic.

Planets

In the "Planet" category of the menu, you will find a list of all the planets added by the mod. Here you can edit the appearance and orbit of any planet, including Earth. Each planet has a list of moons, these can be edited the same way as any planet. You can also add new planets and moons in the config. Custom stars and deepsky objects can be added in a similar way to planets in their own categories.

Using the "Observing Planet" option, you can easily switch the perspective from Earth to any added object in the solar system, including planets, moons, asteroids or even the sun. This shows you how planets / moons appear from planets other than Earth (like Earth from Mars).

Other

• Setting the latitude to a value above 90° will activate dynamic latitude (latitude is decided based on Z coordinate. A globe can be simulated by setting latitude to how many blocks away the poles are from the equator on your hypothetical globe. The stars will now tilt as you walk north or south.
• Background stars can be edited using resource packs, at "assets/astrocraft/stars.txt". If you only want to add a few stars, use the custom star list in the menu.