# Tag Info

## Hot answers tagged coordinate

### Where is it possible to observe the Moon for 24 hours?

Lunar standstill Estimate at what latitudes it is possible to observe the Moon for at least 24 hours. This will depend on the Moon's maximum declination, which varies with a period of 18.6 years (...
• 1,395

### How to describe the Sun's location to an alien from our Galaxy?

This has already been done. The pioneer 10 and 11 probes have a description of the solar system's location and Earth engraved for aliens to understand (or so one hopes). The physical parameters of our ...
• 19.9k
Accepted

### Where is it possible to observe the Moon for 24 hours?

Near the Poles is where unusual things occur. Like, in parts of Greenland, which is pretty close to the north pole, the sun never sets during summers, and the sun never rises during winter. The same ...
Accepted

### How to describe the Sun's location to an alien from our Galaxy?

If the travel was instantaneous (or say, less than a million years) it should be relatively easy to relocate the Sun from triangulation using well-known objects visible from anywhere in the Galaxy. If ...
• 155k
Accepted

### Coordinate system for space

For locating objects in the sky, the horizontal and equatorial coordinate systems are commonly used. These systems describe the position of some object in the sky very well, but do not explain the ...
• 1,681
Accepted

### Coordinates in the Night Sky

The altazimuth system is directly linked to your position on the Earth. It is the “left-right/up-down” coordinates system; the azimuth being the “left-right” (with 0° for North, 90° East, etc.), and ...
• 7,512
Accepted

### How big is one arcsecond at various distances?

How big is one arcsecond at various distances? An arcsecond is a small angle, 1/3600 of a degree or about 5 millionths of a radian ($4.85\times10^{-6}$). To estimate the size of something that ...
• 125k
Accepted

### Local Sidereal Time

LST = 100.46 + 0.985647 * d + long + 15*UT They don't explain what the two constants are (100.46 and 0.985647), could anyone explain what those constants are ...
• 34.1k
Accepted

### How to convert density from physical unit to comoving unit?

You're asking two different, but somewhat related questions: One has to do with a practical way of describing the expansion of the Universe; the other has to do with a way of dealing with our ...
• 38.7k
Accepted

### Where is the North of the Universe

Sort of... There is a system called the International Celestial Reference System (ICRS) which has center at the Solar System Barycenter (normally inside the Sun but not the same as the Sun's center) ...
• 8,442
Accepted

### How can non-earth-orbiting satellite coordinates be obtained by amateurs?

Does a publicly accessible website/API exist that provides the current coordinates for such objects? Yes! There's a pre-launch planning trajectory from ISRO/JPLNAV in the Horizons system. Chandrayaan-...
• 15k
Accepted

### Why is the symbol of Vernal Equinox ♈?

As Wikipedia explains in the article on the Zodiac, the Zodiac was originally developed with the assumption of fixed equinoxes. It is assumed this is because the Babylonians who developed the Zodiac ...
• 6,300