instrumental magnitude

Affiliation
American Association of Variable Star Observers (AAVSO)
Fri, 07/12/2024 - 10:55

I have this quick question: usually the apparent magnitude is introduced as m = -2.5 * log10(F) where F is the apparent brightness of a given star. F is given as

F = (\sum E_xy) / (texp * A),

where texp is exposure time and A is the aperture of the telescope. In a given software, is F actually calculated as the sum of pixel counts (converted to electrons) divided by (texp * A) where texp and A are taken from the FITS header?

If that is true then F has units of e- per second per m^2. Would it be then permissable to take the log10 function of that number? If permissable, is the resulting m the instrumental apparent magnitude?