flux convert from Jy to erg/s/A

The mks units of flux density, W m−2 Hz−1, are much too big for practical astronomical use, so we define smaller ones: 

1 Jansky=1 Jy10−26 W m−2 Hz−110−23 erg s−1 cm−2 Hz−1

and 1 milliJanksy = 1 mJy 10−3 Jy, 1 microJansky = 1  Jy 10−6 Jy. 



PS:
1 erg s−1 cm−2 Hz−1 =  1 dv/dl  erg s−1 cm−2 lambda−1 = c/lambda**2   erg s−1 cm−2 lambda−1

1 Jy = 3E-5 erg s−1 cm−2 lambda−1   /(X)**2
        ~ 1.2 E-(23-11)  erg s−1 cm−2 lambda−1   at  5000A


http://www.cv.nrao.edu/course/astr534/Brightness.html