Can you explain arcs and arcseconds?

Question

I cannot comprehend this subject dealing with astronimical distance.

Answer 1

the circle is 360°. one degree is sixty arc-minutes. one arc-minute is sixty arc-seconds.

Answer 2

If my memory serves me correctly....
An arc is a portion of a circle. When you are talking astronomy, imagine you are at the center of a circle looking outward. Pick 2 points on the circle, and the portion of the circle between them is an arc. You will recall that a circle has 360 degrees. An arcminute is 1/60th of a degree, and an arcsecond is 1/60th of an arcminute (or 1/3600th of a degree). Incidentally, there are degrees, minutes, and seconds of longitude on the globe, based on the same idea. Back to astronomy, however... How big an arcsecond is depends on the distance from the center of the circle. A parsec is the distance at which an astronomical unit subtends one second of arc (1AU=avg distance of earth to sun=93 million miles); so looking out from the center of a circle with a radius of 1 parsec, 1/3600th of a degree will be 93 million miles long. In recent years, the parsec has been replaced in the common parlance by the "light year," probably because it's easier for the average person to comprehend. Hope that helps!

Answer 3

A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60) of one degree. Its subdivision arcsecond comprises one sixtieth of an arcminute.

Since one degree is defined as one three hundred and sixtieth (1/360) of a circle, 1 arcminute is 1/21600 of the amount of arc in a closed circle, or (π/10800) radians. Its usage is limited to those fields which require a handy unit for the expression of very small amounts of arc, such as astronomy.

In the equatorial coordinate system, astronomers typically measure Declination in degrees, arcminutes and arcseconds