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FORD 1K X 3K CCD Available at the Coude...(1Sep94) Spectrograph (from KPNO, NOAO Newsletter No. 39, 1 September 1994) We now have a FORD CCD (F3KB) for use on the Coude Spectrograph. The good news is that it is quite good cosmetically, has excellent charge transfer characteristics, high quantum efficiency, and good linearity and dynamic range. However, there appears to be some mechanism within the device which causes a spill-over of photons and/or electrons into neighboring pixels, limiting the best focus to approximately 2.5 pixels FWHM. Fortunately, the impact for use at the Coude Spectrograph is not severe, as we can get about 2.8 pixels FWHM for a 300 um slit width on camera 5. The resolution profiles are very well fit by a Gaussian. Focus varies slightly across the field of view and is most probably attributable to the camera 5 optics. Daryl Willmarth will realign the optics this summer to see if this focus variation can be minimized. In addition, F3KB does fringe redward of about 7000 Angstrom. Flat fielding of the fringe pattern is probably achievable at the 0.5% level. Fringing is not a problem blueward of 7000 Angstrom. The general characteristics of the F3KB device are given in the table below, along with TI5 characteristics for comparison: CCD Name: F3KB TI5 Pixel Size: 15 X 15 um 15 X 15 um Format: 1024 X 3072 800 X 800 Noise: 7.5 e- RMS 8 e- RMS Gain: 2.5 e-/ADU 4.3 e-/ADU Preflash: Not needed 30 to 100 e- Linearity: 1.5 X 10^5 e- (0.5%) 5 X 10^4 e- (1%) Dark Current: 6 e-/hr pixel 1 e-/hr pixel The quantum efficiency for both F3KB and TI5 devices are shown in the figure. Note that the response of F3KB in the blue is 50% higher than that of TI5. [Figure not included] F3KB will be available for shared risk use this fall for those who desire to use it in place of the CCD assigned for their run on the schedule. For observing proposals for the spring 1995 semester, we ask that F3KB be used in all cases if possible. We will, however, keep TI5 available for any applications which absolutely require the resolution capability of that CCD over the F3KB or for any ultra-high signal to noise observations in the red. Sam Barden, Daryl Willmarth, Di Harmer
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