For the Halpha frames:
1) Measure the counts through some aperture.
2) Correct for exposure time (from the header) so you have counts/sec.
3) Correct to X=0 (above atmosphere) by multiplying by 10.**-0.095*X/2.5
4) Convert to F_lambda [ergs/sec/cm2/A) by multiplying by 2.14e-18
5) If you have an emission-line source (rather than a continuum source)
multiply by 83.69 to obtain ergs/sec/cm^2
For the broad-band filters: