Nomenclature

CCDs are often listed and named by an apparently strange convention. This small section aims to demystify these odd sounding names. CCDs come in various sizes and shapes and are manufactured by a number of companies (see Appendix B).

Figure 1.1 illustrates a number of modern CCDs. Present day CCDs generally come in sizes ranging from 512 by 512 "picture elements" or pixels to arrays as large as 8192 by 8192 pixels. Often the size designations of CCDs are written as 2048 x 2048 or 20482. CCDs are also available as rectangular devices of unequal length and width and with nonsquare pixels. For example, CCDs of size 2048 x 4096 pixels are produced for spectroscopic applications. We will see in Chapter 2 that each pixel acts as an electrically isolated portion of the silicon array and is capable of incoming photon collection, storage of the produced photoelectrons, and readout from the CCD array to an associated computer as a digital number.

The names or designations of CCDs are usually a combination of the company name with the CCD size. Tek2048, 4K x 2K E2V, and SITe4096 are examples. Instrumentation at observatories almost exclusively includes a CCD as the detector and is specialized to perform a task such as imaging or spectroscopy. Observatories designate these instruments with a name that may or may not include information about the associated CCD detector. The Royal Greenwich Observatory (RGO) on La Palma has the FOS#1A (a 512 x 1024 Loral CCD used in their Faint Object Spectrograph), and the Tek 2K CCD of the National Optical Astronomy Observatories (NOAO) is a 2048 x 2048 pixel array used in their 0.9-m telescope imaging camera. Observatories keep lists of each of their instruments and associated CCDs with detailed documentation about the CCD specifications. For examples of such information, check out the observatory websites listed in Appendix B.

Fig. 1.1. A selection of CCDs of the type that are currently used in astronomical instruments at various telescopes throughout the world. Clockwise from bottom left they are: SITe-002 (2048 x 4096), Loral 2k3eb (2048 x 2048), E2V CCD42-80 (2048 x 4096), SITe-424 (2048 x 2048), GEC P8603 (385 x 578), E2V 15-11 (1024 x 256), TeK1024 (1024 x 1024), Loral 512FT (512 x 1024), E2V-05-30 (1242 x 1152), E2V CCD42-10 (2048 x 512), Loral-64 (64 x 64), and E2V CCD39-01 (80 x 80). E2V Technologies was formerly known as Marconi and prior to that as EEV.

Fig. 1.1. A selection of CCDs of the type that are currently used in astronomical instruments at various telescopes throughout the world. Clockwise from bottom left they are: SITe-002 (2048 x 4096), Loral 2k3eb (2048 x 2048), E2V CCD42-80 (2048 x 4096), SITe-424 (2048 x 2048), GEC P8603 (385 x 578), E2V 15-11 (1024 x 256), TeK1024 (1024 x 1024), Loral 512FT (512 x 1024), E2V-05-30 (1242 x 1152), E2V CCD42-10 (2048 x 512), Loral-64 (64 x 64), and E2V CCD39-01 (80 x 80). E2V Technologies was formerly known as Marconi and prior to that as EEV.

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