code: def eclipse_pars(P,M1,M2,R1,R2,ecc=0,inc=90,w=0,sec=False):
      
      a = semimajor(P,M1+M2)
      if sec:
          b = a*AU*np.cos(inc*np.pi/180)/(R1*RSUN) * (1-ecc**2)/(1 - ecc*np.sin(w*np.pi/180))
          #aR = a*AU/(R2*RSUN) #I feel like this was to correct a bug, but this should not be.
          #p0 = R1/R2 #why this also?
      else:
          b = a*AU*np.cos(inc*np.pi/180)/(R1*RSUN) * (1-ecc**2)/(1 + ecc*np.sin(w*np.pi/180))
          #aR = a*AU/(R1*RSUN)
          #p0 = R2/R1
      p0 = R2/R1
      aR = a*AU/(R1*RSUN)
      return p0,b,aR
docs: retuns p,b,aR from P,M1,M2,R1,R2,ecc,inc,w