Analysis of Ccd Properties

Preliminary Analysis of CCD Properties

Group one gathered bias and flat exposures for a 16 bit CCD of 1x1 binning, at a temperature of 263 +/- .2 Kelvin, using a clear filter. Seven bias frames were taken, and data for 23 flat fields were gathered. However, flat field exposures 13-16 were compromised due the dispersing cover falling off the CCD. The CCD had a well capacity of 100,000 electrons, and a manufacture's gain of 2.5 e/ADU, suggesting saturation due to full well capacity at 40,000 ADUs.

Two of the bias frames were analyzed, both in the region [700:800,500:600], yielding mean pixel values of 994.5 and 994.4. The standard deviation of the difference of the two frames were determined using the imarith command in IRAF, which yielded a value of 8.808.

Two of the flat field exposures were selected, number 18 and 25, with the same region analyzed as the two previous bias frames, with mean pixel values of 23,576 and 25407, respectively. The imarith command was again used to determine the standard deviation between the exposures, yielding a value of 147.8.

Gain = [(F1 + F2) – (B1 + B2)] / [sigma2(F1-F2) – sigma2(B1-B2)]

The above equation was used to determine the experimental gain of the CCD, with F1 and F2 as the mean pixel values of each flat field exposure, B1 and B2 as the mean pixel values of each bias frame, and sigma(F1-F2) and sigma(B1-B2) as the standard deviations of the difference between the frames. From the bias and flat fields analyzed, an experimental gain of 2.159 e/ADU was determined.

Gain = [(23576 + 25407) – (994.5 + 994.4)] / [147.82 – 8.8082] = 2.159

Read Noise = [Gain * sigma(B1-B2)] / sqrt(2)

The above equation was used to determine the read noise of the CCD. From the frames analyzed, a Read Noise value of 13.446 ADU.

Read Noise = [2.159 * 8.808] / sqrt(2) = 13.446

In practice, the CCD displays a lesser gain of 2.159 relative the manufacture's claimed 2.5.

In 1x1 binning, the CCD detector reaches...