m := -7.5
M := -19.3

r0 = (10^(((m + 5 - M)/5)))

r0 := 2290.867652767775`
h := 80
b := 14.6  °
l := 327.6

a01*(∫_0^r01) (E^(((-r*
                    Sin[b1])/h1))) \[DifferentialD]r

A[r_, 
        br_] := ((a0*h)/Abs)[Sin[br]]*(1 - (E^(-((r*Abs[Sin[br]])/h))))

Solve[
      A[∞, (π/2)] == 0.128, a0]

a0 := 0.0016

Plot[{(10^(-0.2*(0.128/Sin[14.6  °])*(1 - (E^(-Sin[14.6  °]*r/80))))), r/r0}, {r, 0, 
        2300}]

FindRoot[
      r/r0 == 
        (10^(-0.2*(0.128/Sin[b])*(1 - (E^(-Sin[b]*r/80))))), {r, 2300}]

FindRoot[
      m + 5 - 5 Log[10, 
              r] - (0.128/
                Sin[14.6  °])*(1 - (E^(-Sin[14.6  °]*r/80))) == M, {r, 2200}]

Ab[r_] := a0*r

FindRoot[m + 5 - 5*Log[10, r] - a0*r == M, {r, 2200}]

Δr = 1814.573551499791 - 1053.835248217546

δ = (760.7383032822449/1814.573551499791)