| 3 | | Gene had made a point that the flattening of the SN curve in the 2013-05-09 plots seemed unusual, and that led me to remembering a note I made in my notebook that "sqrt(V) seems to resemble I more than V does". This led to what I believe is the main issue: psphot has a "SOFTEN.VARIANCE" parameter that is applied in the psphotMaskReadout.c file which sets the variance to Vo = Vi + (f * I)^2^. This parameter has a comment in the config file of "XXX drop? soften the errors for bright pixels". However, for the very large flux images I've been examining, Vo ~ I^2 |
| | 3 | Gene had made a point that the flattening of the SN curve in the 2013-05-09 plots seemed unusual, and that led me to remembering a note I made in my notebook that "sqrt(V) seems to resemble I more than V does". This led to what I believe is the main issue: psphot has a "SOFTEN.VARIANCE" parameter that is applied in the psphotMaskReadout.c file which sets the variance to Vo = Vi + (f * I)^2^. This parameter has a comment in the config file of "XXX drop? soften the errors for bright pixels". However, for the very large flux images I've been examining, Vo ~ I^2^, expecially in the core. This forces the S/N image to flatten, prompting the need for the V2 fix to re-add a peak. Disabling this parameter provides a peaked S/N curve. However, this doesn't seem to be the total solution, as switching to a brighter star shows that there is still some ringing in the S/N image. |
