Reduction Steps

The software now available is a package for doing relative calibrations of the pixels, for averaging frames, and for cleaning images. Cleaning in this context means removal of instrumental faults and other defects from the images. A list of the relevant commands is provided for reference in the section B.1.10 of this appendix.

The CCD-reduction involves the steps outlined below. Steps in paranthesis [...] are optional but see the following discussion to determine if they are optional in your particular case.

• [ Remove irrelevant columns of all frames ]
• [ Bias correct all frames ]
• compute an average DARK $\Longrightarrow$ DARK_AVG
• [ remove defects from DARK_AVG ]
• compute an average FLAT $\Longrightarrow$ FLAT_AVG
• dark subtraction $\Rightarrow$ FLAT_AVG = FLAT_AVG - DARK_AVG
• [ remove defects from FLAT_AVG ]
• [ normalize the FLAT_AVG,( see Eq. (B.6)) $\Rightarrow$ FLAT_NRM ]
• dark subtraction $\Rightarrow$ SCIE_FRM = SCIE_FRM - DARK_AVG
• [ remove defects from SCIE_FRM ]
• flatfield the scie-frame SCIE_FLAT = SCIE_FRM/FLAT_NRM
• compute the average of science frames $\Rightarrow$ SCIE_AVG

The sections below describe and discuss the various options which are available to perform the needed operations. These sections discuss bias corrections, techniques for computing averages, techniques for cleaning images and removing specific defects, and finally how to use the COMPUTE command for dark subtraction and flat fielding.