An ultra-thinned 1K x 3K CCD for potential use at the McMath-Pierce Telescope has become available to NSO. Mike Lesser at Steward Observatory will coat and test the chip. As readers may recall, previous chips were afflicted with a resolution degradation problem. It is hoped that the additional thinning of the chip will alleviate this defect. We have requested that the chip receive a single-layer "500" coating. This coating seems to offer the best compromise between blue and red response. It has excellent QE near the K-line, while still retaining very good QE in the red, ranging from about 90 about 65 the "600" coating, which is more optimized for the red but drops off a bit more in the blue. With a single-layer coating there will be the prospect of adding another, second layer in the future that will improve QE even more while not having the same maintenance issues that the current double-layer coated chips are confronting.
Mark Giampapa, Dave Jaksha, Jeremy Wagner