2013-10-21

psphot call	-recipe PSPHOT DIFF	-recipe PSPHOT DIFF -Db LMM_FIT_CHISQ_CONVERGENCE F -Di LMM_FIT_GAIN_FACTOR_MODE 2
Angle
Angle vs L
Flux
Flux vs L
L1
L2

2013-02-27

The initial guess for L is in general too large for point-like objects. First, there's an error in the code that chooses between the elliptical major axis and the first radial moment, resulting in a large initial guess. Fixing this doesn't completely work, so the idea was to introduce an offset, such that an object with a size similar to the width is probably point like, so we should normalize by subtracting that width off. This shrinks the length again, but insufficiently. Looking at large numbers of objects (click on full skycell tables in attachments below), it's clear that dL/dIteration is almost universally positive, suggesting an issue with the calculation (typo in the code?) or algorithm.

Example: Original:

    float size = (axes.major > source->moments->Mrf) ? axes.major : source->moments->Mrf;
    PAR[PM_PAR_LENGTH] = 1.5*2.35*size; // a tophat of length L has L = 1.5 * 2.35 * sigma                                  

#X         Y           ID    Mxx       Mxx      Myy       Mr1        EXT_F     EXT_L     EXT_W    EXT_Q     PSF_CHISQ   PSF_NDOF    EXT_CHISQ  EXT_NDOF
77.558716 2633.799072 -98 : 11.551100 1.738350 10.857200 6.066510 : 16.974348 32.950000 1.984060 0.725825 : 3286.150000 2600.000000 3207.900000 2892.000000
       #IT F         L         W        Q          oChi        nChi        delt     dlin      rho      lambda
         0 62.666386 21.384449 1.984059 0.686898 : 5817.757812 3362.864990 nan 1238.471436 1.982196 0.001000
         1 16.869297 22.949951 1.984059 0.686511 : 3362.864990 3327.216797 0.849738 22.782276 1.564734 0.000250
         2 16.829279 24.949951 1.984059 0.689350 : 3327.216797 3292.971436 0.012339 20.549458 1.666485 0.000063
         3 16.904570 26.949951 1.984059 0.697310 : 3292.971436 3260.270020 0.011854 18.246912 1.792162 0.000016
         4 16.923841 28.949951 1.984059 0.710121 : 3260.270020 3231.121338 0.011319 16.398548 1.777516 0.000004
         5 16.916101 30.949951 1.984059 0.721472 : 3231.121338 3207.896484 0.010090 12.160172 1.909912 0.000001
        XX 16.974512 32.949951 1.984059 0.725825 : 3207.896484

Sqrt:

    float size = (axes.major > sqrt(source->moments->Mrf)) ? axes.major : sqrt(source->moments->Mrf);                 
    PAR[PM_PAR_LENGTH] = 1.5*2.35*size; // a tophat of length L has L = 1.5 * 2.35 * sigma                                  

#X         Y           ID    Mxx       Mxx      Myy       Mr1        EXT_F     EXT_L     EXT_W    EXT_Q      PSF_CHISQ   PSF_NDOF    EXT_CHISQ  EXT_NDOF
77.559525 2633.799561 -103 : 11.602900 1.715950 10.896300 6.099250 : 17.214936 29.877100 1.992040 0.654534 : 3400.710000 2600.000000 3371.800000 2917.000000
       #IT F         L         W        Q          oChi        nChi        delt     dlin      rho      lambda
         0 62.998722 12.710316 1.992041 0.683864 : 4785.610352 3625.804443 nan 586.573059 1.977257 0.001000
         1 19.728992 13.877067 1.992041 0.690744 : 3625.804443 3593.194092 0.398012 14.094786 2.313647 0.000250
         2 19.357067 15.877067 1.992041 0.688212 : 3593.194092 3559.262207 0.011191 14.204083 2.388882 0.000063
         3 18.790325 17.877068 1.992041 0.654087 : 3559.262207 3522.943359 0.011644 17.820257 2.038065 0.000016
         4 18.215334 19.877068 1.992041 0.623698 : 3522.943359 3488.975830 0.012464 18.180664 1.868333 0.000004
         5 18.069387 21.877068 1.992041 0.611393 : 3488.975830 3458.826904 0.011657 14.959837 2.015325 0.000001
         6 18.013340 23.877068 1.992041 0.616009 : 3458.826904 3429.208984 0.010346 14.725613 2.011320 0.000000
         7 17.703453 25.877068 1.992041 0.629182 : 3429.208984 3399.503418 0.010164 16.940977 1.753474 0.000000
         8 17.366875 27.877068 1.992041 0.643639 : 3399.503418 3371.803467 0.010194 17.004745 1.628954 0.000000
        XX 17.215097 29.877068 1.992041 0.654534 : 3371.803467

Adjustment:

    float size = (axes.major > sqrt(source->moments->Mrf)) ? axes.major : sqrt(source->moments->Mrf);                 
    if (size > psfAxes.major) { size -= psfAxes.major; }                                                              
    else { size = psfAxes.major; }                                                                                        
    PAR[PM_PAR_LENGTH] = 1.5*2.35*size; // a tophat of length L has L = 1.5 * 2.35 * sigma                                  
#X         Y           ID    Mxx       Mxx      Myy       Mr1        EXT_F     EXT_L     EXT_W    EXT_Q   PSF_CHISQ   PSF_NDOF    EXT_CHISQ  EXT_NDOF
77.559189 2633.799561 -98 : 11.558200 1.736740 10.870700 6.072910 : 5.257746 7.728160 1.978440 0.787694 : 2631.840000 2600.000000 836.549000 824.000000
       #IT F         L         W        Q          oChi        nChi        delt     dlin      rho      lambda
         0 62.719723 5.728158 1.978445 0.687694 : 3845.604736 3837.298584 nan 124.292549 0.066827 0.001000
        XX 5.257778 7.728158 1.978445 0.787694 : 3837.298584