IR Binning
At the start of the 2003B observing semester, IR data taken with ANDICAM on the SMARTS 1.3m telescope will be binned 2x2.
The IR CCD is a 1024x1024 device. The 18-micron pixels have an image scale of 0.137-arcsec/pixel at the 1.3m telescope. Given the typical seeing of 0.37 arcsec/pixel, we will be binning the IR images 2x2, giving it 36-micron effective pixels and a more reasonable image scale. Pending any convincing arguments otherwise, binning will be mandatory starting in the 2003B observing semester. Please email Prof. Charles Bailyn concerning this matter.
The process we will take to perform this operation will be to first apply a bad pixel mask to the raw images with the IRAF routine FIXPIX. A bad pixel mask was created from the ratio of a bright skyflat (combination of five bright J skyflats) to a dark image (combination of five 60s darks) using CCDMASK. This (1024x1024) mask can be seen here. After applying the bad pixel mask, the images will be binned 2x2 using BLKAVG. For future reference with binned data, the binned version (512x512) of the bad pixel mask can be seen here.
To see an example of this procedure, we present images of processed data both before and after the mask/binning procedure. Both examples have been created by first processing and then combining the individual images. The examples are zoomed in to show more detail. The first example shows the processed data with no mask applied and no binning. The second example shows the processed data after a mask was applied to the individual raw images and then binned. Close examination reveals the absence of "snowy" pixels in the binned image, which have been removed by the bad pixel mask application prior to binning.
No mask applied, no binning.
Mask applied, binned 2x2.