CFHT Information Bulletin, number 38, First Semester 1998

Optics Group Report

Greg Barrick, CFHT (


Because of multiple complaints that the OSIS slow guiding is not working properly, the system has been investigated and a swapped cable discovered on the APDs. The system was re-tested on the Mezzanine and during engineering time and seemed to work fine. More complaints, however, have come up as well as the failure of the guider to work with TCS VI, so additional test are planned for after the November run which will hopefully resolve these issues finally.

Also, pupil masks have been defined and cut for each grism. These should be installed and tested before the February run. These are being installed to help reduce scattered light in the MOS and OSIS spectrographs.


The auto-focus unit for LAMA is nearly complete. The unit has been run successfully many times by CFH staff and should be ready for release to observers by the February MOS run. See the accompanying article by Jon Seerveld for further details on the LAMA auto-focus.

LAMA was used many times in the support of instruments other than MOS/SIS. Many masks were cut, some on very short notice, for both OASIS acceptance testing and for the multi- diaphragm mask used for the micro-lens array. Also, the Lyot stop used in KIR was cut using LAMA and cold tested at CFHT before being sent to Montreal for integration.


OASIS has had its first successful on-the-sky engineering run. The first engineering run was weathered out, but the second one had good weather. The instrument performed well during this run and much useful performance data was taken during this time including flexure, throughput, and image quality. In all of these cases, the instrument performed at least as well as expected. There are still some software problems and some small hardware problems to be worked out before and during the commissioning run in January. See the accompanying article by Pierre Martin for more details.


The Gumball upgrade project is nearly completed. The upgraded optical path was installed and tested successfully during the November MOS run. The electronics and control software are nearly completed as is the Fabry-Perot calibration source. It is planned that the new Gumball system will be installed, tested, and ready for the January OASIS run. For details, see the accompanying article by Greg Barrick


The new V, R, and I band beamsplitters are still being fabricated. The beampslitters have been tested for surface quality and radius of curvature by NRC-Ottawa and have been accepted. They are currently at APS and the final design of the coatings is being done. The I beamsplitter has had its reflective coating applied and it looks good. It still needs an AR coating applied, but it should arrive by around mid-January. The others are still being processed and could need several months to be completed.

Summit Coating Chamber

The summit coating chamber has been test fired to determine the suitability of some new aluminum clips which are of a different mass and hardness than the clips previously used. The firing was successful and the proper loading of the filaments with the new clips has been determined.


The new Loral 5 CCD has been installed and tested on Gecko and was used for the October Gecko run. The tests showed that the QE was better than Loral 3 by a factor of 2-3 times for most wavelengths as expected and that the QE appears to be stable. The tests also showed the onset of fringing at ~6800 Å with the fringing reaching a plateau of about 28% (peak-to-peak) at ~8500 Å. Finally, we found that the image quality (slit image size) degrade by ~20% with Loral 5 due to the MTF degradation expected with thinned CCDs. We have not seen a clear wavelength dependance to this degradation, but we did not thoroughly explore all possible wavelengths.


Several staff members have been trained by Gerry Luppino on the operation of the UH8k, especially the shutter mechanism, to allow for faster response time from CFHT in the event of UH8k malfunctions.

Editor: Dr. T. M. C. Abbott,
Copyright © 1998, CFHT Corporation. All rights reserved.