Last Newsletter we had the "Bad and the Ugly," so it's only natural that we have the "Good" this time. Firstly, we have purchased a Grade 1 SITe 2048 CCD. This is a thinned device, with four low-noise amplifiers and near-perfect cosmetics. It has the "standard" SITe AR coating and thus has QE over 60% from 3900Å to 8700Å, peaking at 80% in the red. This CCD will replace the failed (Tek 2048 #4) CCD, with use mostly for 4-m imaging and echelle spectroscopy. Tests in the detector lab and at the telescope confirm the high quality of the new CCD. All that remains is to tweak a few voltages in order to optimize full-well behavior before releasing for general use.
Secondly, our STIS 2048 CCD, used at the Schmidt, suffered broken bond wires when a bolt became detached inside the dewar and its associated washer ended up on the CCD surface. Observers over the two weeks following the incident had to make do with a variety of CCDs but since then most have been scheduled with Tek 2K #5, a thinned CCD with high QE but large pixels. We took the opportunity to remove the cracked coating (see NOAO Newsletter No 50. p9) before sending the damaged STIS CCD to Mike Lesser (Steward Observatory) for re-attachment of the bond wires. The CCD was then re-coated by Kirk Gilmore (Lick Observatory). A second, spare STIS 2048 CCD was coated at the same time. Tests indicate that our original STIS is now working on two amplifiers only. The second CCD also only has two low-noise amplifiers, but rather better cosmetics, and will likely be the one chosen to be installed at the Schmidt. The doubling of the read time implied by the use of two amplifiers rather than four (to approximately one minute) will unfortunately lower observing efficiency.
Alistair Walker, Roger Smith