In article , "PoorRichard"
writes:

We need one additional piece of information. Are these objects and
cosmologically significant distances?

Ah yes, that is important! The objects (type 2 AGN) are fairly local; z
0.03. I am dealing with cm wavelength.

OK, the cosmological redshift is negligible; that makes things a lot
simpler.

Next question.

Are you interested in the number of objects of a given absolute
luminosity per volume, or the number of objects of a given apparent
magnitude per redshift interval? This doesn't really matter since the
conversion is trivial at these redshifts, but it might simplify the
discussion.

Important questions: what is the actual problem you are workin on? How
large is the data set? What are the selection criteria and how complete
is the sample?