| Returns float holding great circle distance between two points (ra1,dec1) & (ra2,dec2) |
| The great circle distance is in arcmins, the ras and decs are in degrees. |
| Name | Type | Length | inout | pnum |
| @ra1 | float | 8 | input | 1 |
| @dec1 | float | 8 | input | 2 |
| @ra2 | float | 8 | input | 3 |
| @dec2 | float | 8 | input | 4 | float | 8 | output | 1 |