The CCD that we used is composed of about 1 million pixels (or 1056 by 1024 pixels to be exact). Each of these pixels is essentially its own detector that detects incoming photons. The CCD's surface is made of silicon. This silicon surface provides the CCD with the photoelectrons that is captured within the pixel wells. Incoming photons with the correct wavelength strike this semiconductor surface which emit photoelectrons due to the photoelectric effect. These photoelectrons are then captured in the potential well of the pixel and stored so it can be read after the exposure is finished. After the image is taken, the CCD starts reading out the data for each pixel by means of an Analog-to-Digital (A/D) converter. The A/D converter reads out the data by measuring the charge collected by each pixel and converting this measurement to a digital readout. Since it would be difficult to place an A/D converter at each individual pixel, CCD's work by systematically transferring the charges from each pixel, effectively moving all of the collected photoelectrons from each pixel toward the measuring device. The signal is amplified to increase the signal strength then measured by the A/D converter. The CCD reads out data in Analog-to-Digital Units (ADU), which is sometimes referred to as Digital Numbers (DN). I will discuss this property of CCD's more in Section 3.4.
We were able to control the CCD through a local computer using a software package called MaxIm DL. This program allowed us to control the temperature of the CCD, the exposure time, and whether or not the shutter opens during the exposure. We also used a Visual Basic script written by Dylan Nelson to run the CCD and automatically take images at different exposure times and then save them as fits files on the local computer.