Basic declination calculator
This calculator uses the same formulae as “GETDEC”, the program referred to in Astronomy in Prehistoric Britain and Ireland (p. 169) and in various publications by myself and others.
The original program is no longer accessible.
Except in discussing putative high-precision lunar phenomena, the apparent declination is sufficient for all archaeoastronomical purposes. While the program quotes results to arc-second precision, a precision of 0.1 degrees (6 arc minutes) is quite sufficient in most contexts.
The program applies a mean refraction correction to the observed altitude and (for geocentric lunar declinations) mean lunar parallax.
See the Astronomy boxes in Astronomy in Prehistoric Britain and Ireland for more information.