DECam--What?

Main Characteristics of Focal Plane

Field of View  3 square degree (2.2 degree field of view)
Pixel scale  0.27 arcsec/pixel (15 microns)
Detector  62 2048x4096 science CCDs, 520 megapixels total (570 Mpix including guide and focus CCDs)
Read-out noise  7e-
Read-out time  30-40 seconds
Dark-current ~<25 e-/pixel/hr (spec)
Dynamical range  16 bit
CCD Gaps  3.0 mm (201 pixels) along long edge (e.g., between S4 and N4); 2.3 mm (153 pixels) along short edge (e.g., between N4 and N5)
Cosmetics  Good to excellent.  On average, each CCD has 0.05% bad pixels and the worst CCD has 0.39% bad pixels.
Filters  6 filters now available (ugrizY)
Gain  4.5 e-/ADU (typical, provisional 2012-Nov)
Non linearity, < 1% (provisional/conservative) For normal observing, keep level below 100,000 e-, 22,000 ADU
Raw data format  Fits (with extensions),1 GB/file, ~600 Mbyte/file compressed
Telescope aperture  4m
Telescope focus  Prime
Instrument F ratio  f/2.7

The figure below shows the orientations on the sky and spatial footprint of the focal plane array.

The 2k x 2k CCDs labeled as "F" are used for focus and alignment control; those labeled as "G" are used for guiding.  The detector position numbers (e.g., "S4" or "N4" near the center of the field) are useful for identifying specific CCDs to look at in the multi-extension images, like "display DECam_00153116.fits[N4]").  

When working with the data, both at the telescope (real time display) and off disk (default ds9 view), the images are often displayed in "pixel orientiation".  The figure below shows the orientation of the field and CCDs in pixel orientation.

Example images can be downloaded from the NOAO science archive.

Here is the pixel data array in DECam FITS files (pre-scan and overscan regions are shown).

Here is the pixel scale distortion map (courtesy Mischa Schirmer)