/*      FILE:  phot_mag.c
 *   PURPOSE:  Calculate the stellar magnitude.
 *    AUTHOR:  Kenneth J. Mighell (mighell@noao.edu)
 *  LANGUAGE:  ANSI C
 *      DATE:  2001JUL03
 * COPYRIGHT:  (C) 2001 Assoc. of Universities for Research in Astronomy Inc.
 */

#include "mx.h"
#include "qdphot.h"

int qdphot5_PhotS_CalcMag_f2 (
  qdphot5_ImageS *Image,
  qdphot5_PhotS *PhotS
){

  char mxfunc[] = "qdphot5_PhotS_CalcMag_f2";
  int status = -1;

  double ebkg;
  double area;
  double sgnl;
  double esgnl;
  double electrons;
  double ron;
  double flux;
  double mg;
  double emg;
  double cmg;
  double mnsnr;
  double mmag;

  ebkg = PhotS->ebkg;
  area = PhotS->area;
  sgnl = PhotS->sgnl;
  ron = Image->ron;       /* CCD readout noise */
  mnsnr = Image->mnsnr;

  if (sgnl <= 0) goto bye;

  electrons = sgnl;
  esgnl =
    sqrt( 
      electrons           /* random error due to photon noise */
      + (area*(ron*ron))  /* random error readout noise */
    ) + (area*ebkg);      /* systmatic error due to sky measurement error */

  /* magnitude */
  flux = sgnl;
  mg = 99.999;
  emg = 99.999;
  if (flux > 0) {
    mg = -2.5*log10(flux);
    emg = 1.0857*(esgnl/sgnl);
  }

  /* check magnitude */
  flux = mnsnr*esgnl;
  cmg = 99.999;
  if (flux > 0) cmg = -2.5*log10(flux);

  if (mg<cmg) status = 0;

bye:

  PhotS->mg = mg;
  PhotS->emg = emg;
  PhotS->cmg = cmg;

  return( status );

}
/* end-of-file */