Selection according to the coordinates (alpha, delta)

The selection can be performed over right ascension only, declination only or on both simultaneously. The options -gt (larger), -lt (smaller), and -i (between) may be used for selection on right ascension or declination. Option -i only is allowed with the double selection. The latter perform a selection in a box defined by two RA and two Dec limits. One needs also to precise the parameter keyword:

alf for the right ascension,
dec for declination,
ad for the double selection on ascension and declination.

The command ocl needs one limit for the options -gt et -lt, two limits for the option -i, and four limits for the option -i and the keyword ad. The smaller value should always be given first.

Examples:

ocl alf -gt 23 select clusters with right ascension larger than 23h
ocl dec -i 10. 20. select clusters with declination between +10 and +20 degrees
ocl ad -i 0. 1. 5. 10. select clusters with right ascension between 0h and 1h declination between and +5 et +10 degrees