[Aavso-photometry] Differential vs. absolute magnitudes

[gianlucaros at gmail.com]

I have been doing some differential CCD photometry with a V filter.
Since I would like to increase precision I am thinking of buying a B
filter and to use transformation coefficients. Reading the AAVSO
manual I haven't a clear picture on how to trasform differential
magnitudes into absolute one. Once the data have been transformed
using transformation coefficients, shall I calculate zero point to get
the absolute magnitudes? What is the procedure? Are absolute
magnitudes only possible with all sky photometry or all sky photometry
is compulsory only if the comparisons stars are more than a field
apart? I am getting a bit confused.

Gianluca (RGN)