Positional astronomy?

Question

The star grouping Leo (the lion) extends for about 30° along and close to the celestial equator. At low to mid-latitudes, roughly how long does it take Leo to rise above the horizon?

Answer 1

OK, Everyone knows that the sky rotates around the fixed and stationary Earth once every day, and there are 24 hours in a day and 360 degrees in a circle, so 360/24=15 degrees per hour, right? So if Leo is 30 degrees wide, and Leo is stuck onto the crystaline orb known as the sky, then it takes about two hours to rise, correct? Every caveman and cavewoman knows these things.
P.S. Leo is 30 degrees wide, not 30 seconds wide. The human naked eye cannot resolve anything smaller than one degree or 3,600 seconds in size, so if Leo were only 30 seconds wide, it would be WAY TOO SMALL to see, except with a powerful telescope.

Answer 2

Mister sciencenut, chill, huh? Nobody's born knowing ANYTHING other than how to schit and cry, and certainly not the fact that Leo takes about 2 hours to rise. And her question DOES read 30 degrees, not thirty seconds. Maybe it's unintentional, but your response really sounds like you are talking down to her.

Oh, and maybe I wasn't born knowing it, but I wasn't very old when I learned that the moon and sun are about 1/2 degree in diameter from our point of view, and I certainly can resolve a lot of detail on the moon. Visual resolution in humans extends down below an arc minute, 60 times finer than one degree.

Answer 3

positional astronomy is the branch of astronomy that is used to determine the location of objects on the celestial sphere, as seen at a particular date, time, and location on the Earth. This is one of the oldest branches of astronomy. It relies on the mathematical methods of spherical geometry and the measurements of astrometry.

This is the oldest branch of astronomy and dates back to antiquity. Observations of celestial objects have and continue to be, important for religious and astrological purposes, as well as for timekeeping and navigation. The science of actually measuring positions of celestial objects in the sky is known as astrometry.

The primary elements of spherical astronomy are coordinate systems and time. The coordinates of objects on the sky are listed using the equatorial coordinate system, which are based on the projection of the Earth's equator onto the celestial sphere. The position of an object in this system is given in terms of right ascension (α) and declination (δ). The latitude and local time can then be used to derive the position of the object in the horizontal coordinate system, consisting of the altitude and azimuth.

The coordinates of celestial objects such as stars and galaxies are tabulated in a star catalog, which gives the position for a particular year. However the combined effects of precession and nutation will cause the coordinates to change slightly over time. The effect of these changes in the movement of the Earth are compensated by the periodic publication of revised catalogs.

To determine the position of the Sun and planets, an astronomical ephemeris is used. This gives the positions of these objects on the celestial sphere at a particular date and time, which can then be converted into suitable coordinates.

The unaided human eye can detect about 6000 stars, of which about half are below the horizon at any one time. On modern star charts, the celestial sphere is divided into 88 constellations. Every star lies within a constellation. Constellations are useful for navigation. Polaris lies close to due north to an observer in the northern hemisphere. This star is always at a position nearly over the north pole.