Impact of Simple Dithering on Co-Added Depth

March 10, 2010Krughoff, Jones, Ivezic, Connolly

Testing Framework

• Focal plane:– $LSST_SVN/imsims/raytrace/focalplanelayout.txt

• Postgres DB with OpSim 1_29 and 3_61• Python code to add dithered centers• PGSphere for spherical indexing• Join of OpSim field centers and rotator positions

with focal plane layout.• Grid sky and query at each position for

observations.

OpSim 1_36 r-band180 < RA < 220; -30 < Dec < 10

Dithering requirements• Full field dithering• Completely deterministic• Preserve same night pair overlap

Dithering algorithm:• Number nights• Number vertices• Night number%Max vertex number = Vertex number• Apply offset to all OpSim field centers for given night.

Differential and cumulative distributions of 10 year co-added 5 sigma limiting magnitude in r-band. For

reference, the SRD value is 27.5.

Visit Histograms

Power spectra for Dithered and Non-Dithered cases.

Preliminary

Priorities for Future Work

• Further analysis of current dithering scheme– Larger area– Additional metrics

• Proposal aware dithering schemes• Different dithering approaches• Include vignetting