1. Fast photometry  :

• find pixels on lapalce frame > T_n  ( currently T_n = 3.5 sigma )
• find cluster on laplace - all near pixels > T_n and choose the one with greatest value
• on raw data find maximum N pixels ( N = 12 ) :
  
                           xxx
                           xxx
                           xxx
  
  
  x - pixels are always taken, and 3 more are added
  
  
• finds pixels around N pixels with specified break B ( =1 ) , o width W=2, example :
  
  
                            OOOO
                           OBBOO
                         OBBxBBO
                        OBxxxBOO
                       OBxxxxBBO
                       OBBxxxxBO                       
                        OBBBBBBO
                         OOOOOO
  
  this drawing is only schematic - not proper for W=2, and B=1
  
  
• sums pixels in cluster x and finds median in cluster O
• calculates V= Sum(x) - count_x * Median(O)
  NOTE : Median is special median : sorts elemtents , and finds median of first 0.75 of all elements number
  
• calculates magnitudo as : m = MAG_0-2.5*log10( V );
• X,Y  coordinates of star are calculated as center of mass of N pixels ( plus pixels )
  
  
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2. Testing is described here.