SDF Data Reduction: Procedure of primary data reduction (by Dr. Shimasaku, March 2003)

Data Reduction Flow
Data reduction is based on the reduction package "NEKO" for Suprine-Cam mosaic data. (For package details, contact Dr. M. Yagi )
1 Inspect frames Confirm object frames,
select frames for flat-fielding,
identify bias or dark frames
No bias, dark frames are used for curent reduction.
2 Subtract bias Values in an overscan region of CCD chips of Suprime-Cam indicate bias level, which are subtracted from image region.
3 Trim overscan region Unneccessary overscan region
4 Apply mask Find and replace bad pixels with special values, which values are not used in the following reduction.
5 Create flat frames Create flat-field frames for correct for sensitivity variation of CCD chips. Basically flat-field frames are created from object frames.
6 Flat-fielding Flat-fielding object frames.
7 Distortion correction Correct for large image distortion peculiar to Prime-focus.
8 Matching PSF Seeing size of each frame must be matched to each other before frame stacking. Currently, Gaussian smoothing is applied to each frame to match PSFs of all frames, which
have been determined by detected stellar sources.

9 Subtract sky values Before stacking object frames, sky value is subtracted from each object frame.
10 Matching object frames Obtain relative positions and gains
among all frames, using position and flux of stars in the overlapping area.

11 Mosaicing Regarding to relative positions and gains obtained in procedure #10, all object frames are stacked to make a single large image with a size of 5x2 CCDs. Mosaiced large image must have a sky level of zero.
12 Calibration with standard stars