CCD Mosaic Imager Status

The CCD Mosaic Imager continues to evolve toward a mainline facility instrument. Fourteen nights of science observing are scheduled with the Mosaic at the 4-m this semester, and 27 nights at the 0.9-m. We had two engineering/checkout nights before the 4-m runs in September, and two more of these nights in October. For the 1998A Semester (February-July 1998), we received 18 Mosaic 4-m proposals for 66 nights, plus nine Mosaic 0.9-m proposals requesting 61 nights. Some specific areas of progress are:

• The IRAF Data Capture Agent, which automatically transfers images from the data acquisition computer to the data reduction computer, is in routine use. In addition, postprocessing capability was added for the October block. This postprocessing is controlled via the new Data Capture Agent GUI. For now, the primary functionality is the automatic display of the image upon readout. Via the GUI, the observer can turn this option on or off, resize the image display to optimize it for speed or resolution, and view the status of the readout. The next major steps to be included with postprocessing are automatic log sheet generation and data taping.

• We received and tested four new Mosaic filters: three Ha redshifted (6611/81, 6652/81, 6691/83), and [OIII] (5021/56). The [SII] filter (6730/81) did not meet specifications (primarily due to a crack), nor does the [OIII] off-band (5315/290). We are retaining the originals while the vendor fabricates suitable replacements. In addition, we are in the process of procuring the following filters: Johnson U, [OIII] redshifted, and Sloan g', r', i', and z'.

• We have upgraded the two Exabyte drives on the data reduction computer, Driftwood, for increased speed. The new drives are Exabyte Eliant 820s. They can write a Mosaic image using the IRAF task `mscwfits' in just under 3 minutes, about twice as fast as the former Exabyte drives. Tapes written with the Eliant 820s are readable by Exabyte 8505s. We continue to offer the faster DLT-7000 tape drive (1.25 minutes per Mosaic image), and we are gaining experience in writing and reading DLTs.

• As discussed in previous Newsletter articles, we plan to replace the current engineering-grade CCDs with thinned science-grade CCDs from SITe. Two of these science-grade CCDs have now been received. Initial testing shows excellent cosmetics, charge-transfer efficiency, readout noise, surface flatness, and quantum efficiency. We expect the other six needed CCDs over the next several months. As of this writing (late October), we expect that the upgrade to science-grade CCDs will be completed during June or July 1998. We will keep users and proposers informed of progress through the Newsletter and the Mosaic Web page (http://www.noao.edu/kpno/mosaic/mosaic.html) .

• Excellent image quality was seen on several occasions during our September 4-m run. The tightest images had FWHM of 0.65" in the R band across the entire 36' x 36' field, demonstrating the image quality improvement offered by the new corrector.

• The IRAF data reduction tools have been enhanced and improved (see following article). A sample fully reduced Mosaic image is shown in the Figure.

Taft Armandroff, George Jacoby, Todd Boroson
(for the Mosaic Team)