May 7,2002 Update - added analysis of saturated R1 repeats from WSDB.
The estimated magnitudes for 8 R1 saturated sources measured in the V3 calibration scans are plotted vs shape with and without the shape correction. The slope vs shape is well explored and the necessity for the shape correction is evident. These sources range from mag 4 to 5.5 in J and 3.5 to 4.5 in H and Ks. The seeing corrections for brighter sources cannot be validated with this data set.
Five of these sources have some unsaturated measurements in one or more bands, and offsets can be seen between the saturated and unsaturated measurements at good seeing.
These measurements are from the V3 Calibration Point Source database, and have all calibration corrections applied except for the saturated r1 shape correction. There are a total of 11252 measurements for these 8 sources.
The unsaturated measurements have little or no slope vs shape.
The last 2 sources include measurements from both hemispheres.
The per source dispersion was computed for the repeat measurements of the saturated r1 sources in the WSDB. The following plots show the standard deviations vs magnitude for the 1153 saturated sources with repeat measurements without and with shape corrections. The average deviations were as follows:
J H Ks
uncorrected 0.116 0.121 0.115
corrected 0.090 0.087 0.088
The upper plots are the uncorrected standard deviations, the lower plots are with the shape corrections applied.
See Kevin Xu's web pages detailing the saturated r1 magnitude estimation methods and the shape corrections. Also see Brant Nelson's analysis of saturated R1 seeing corrections detailing the 2MAPPS V3 pipeline saturated r1 magnitude estimation and the shape corrections.
This page last updated on May 7, 2002.
Gene Kopan - gene at ipac.caltech.edu
