I've been studying astronomy and I've encountered 3 different (sexagesimal) ways to write angles.
hh mm ss - hours minutes and seconds
dd '' '''' - degrees, arcminutes and arcseconds.
+/- dd mm ss -
For example most sources give the right ascension of an object in the first format while the declination is given in the third.
Why are two coordinates that usually come together given in two different ways?
How can one convert each one of the formats in to decimal degrees?