CCD MOSAIC Imager Status

During May through July, the CCD Mosaic Imager continued to evolve toward a user-class facility instrument. Engineering runs took place at the 0.9-m and 4­m, followed by shared-risk science observing. Two groups used the instrument at each telescope. The observers achieved a high degree of scientific success with the Mosaic. In turn, the Mosaic team received valuable feedback from the observers, and a number of issues raised are being addressed this summer. Some highlights of the runs were:

• Excellent image quality was seen during the 4-m run. The tightest images had FWHM of 0.65" (2.6 pixels) in the R band. This demonstrates that the new 4-m Corrector and ADC are performing well in demanding conditions.

• The IRAF Data Capture Agent, which automatically transfers images from the data acquisition computer to the data reduction computer, was used routinely during the most recent 4-m and 0.9-m runs. The image is available for analysis within seconds of the readout completing (125s for unbinned readout).

• Commands for obtaining multiple dithered exposures have been added to the Arcon IRAF user interface: mosdither and mosgrid. They automatically offset the telescope over a dither pattern or grid, take exposures, and assist with recordkeeping and guider control. The default pattern designed to fill in the gaps between the CCDs proved popular.

• We received two new Mosaic filters, I and H (6563/80), and tested them at the telescope. These join B, V and R. We are scheduled to take delivery and test six other Mosaic filters over the summer (three Ha redshifted (6603/80, 6643/80, 6683/80), O[III] (5007/50), O[III] off (5300/250), and S[II] (6723/80)). However, deliveries have been running somewhat behind schedule.

• As described in the last Newsletter article, we decided to embrace digital linear tape technology to record the vast amount of data produced by the Mosaic Imager. A DLT-7000 tape drive has been installed on the data reduction computer, and a second drive is present downtown on Ursa. IRAF can write the multi-extension FITS files produced by Mosaic to the DLT-7000. We were pleased by the speed of one Mosaic image per minute to the DLT. We offer two Exabyte 8505 drives on the data reduction computer as well.

We are awaiting the thinned science-grade CCDs from SITe, to replace the current engineering-grade CCDs. As of late July, none has been delivered. We continue to work on documenting the CCD Mosaic Imager for users. Progress has been made on the manual sections describing the acquisition software (author Steve Heathcote) and the data reduction software (author Frank Valdes). This documentation is available in draft form on the Mosaic Web page http://www.noao.edu/kpno/mosaic/mosaic.html.

The CCD Mosaic Imager will continue to be offered for shared-risk observing during the first semester 1998 (see the list of instruments in the SCOPE section for guidelines). For more information about Mosaic status or performance, see the Mosaic Web page or contact one of the undersigned.

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