David F. Hilyard

The DEIMOS spectrograph for the Keck II Telescope: integration and testing

The DEIMOS spectrograph is a multi-object spectrograph being built for Keck II. DEIMOS was delivered in February 2002, became operational in May, and is now about three-quarters of the way through its commissioning period. This paper describes the major problems encountered in completing the spectrograph, with particular emphasis on optical quality and image motion. The strategies developed to deal with these problems are described. Overall, commissioning is going well, and it appears that DEIMOS will meet all of its major performance goals.

COSMIC: A Multiobject Spectrograph and Direct Imaging Camera for the 5 Meter Hale Telescope Prime Focus

We describe the design, construction, and operation of the Carnegie Observatories Spectroscopic Multislit and Imaging Camera (COSMIC) for the prime focus of the Hale 5 m telescope at Palomar Observatory. COSMIC is a reimaging grism spectrograph with a 13.65 arcmin square field of view, which can also be used as a direct imaging camera with a 9.75 arcmin square field of view. The wavelength coverage extends from 350 nm to almost 1 mm; the detector is a thinned, back-illuminated SITe CCD with high quantum 2048 # 2048 efficiency and excellent cosmetics. Multislit aperture masks are produced photographically, with spectra of up to ∼50 objects fitted on a single row of a slit mask. The instrument exhibits very little flexure and uses an active thermal control to maintain focus over a wide range of ambient temperature. In direct mode COSMIC is typically used with Kron-Cousins, Gunn, and narrow bandpass filters. The instrument achieves throughputs of greater than 50% for direct imaging and, in spectroscopic mode, a peak efficiency at 5500 A u of slightly better than 24% of light falling on the 5 m mirror. COSMIC is optimized for faint-object imaging, down to Gunn mag, and r 26 multiobject spectroscopy, down to mag, with typically 30 objects per spectroscopic exposure. r 23

The low-resolution imaging spectrograph red channel CCD upgrade: fully depleted, high-resistivity CCDs for Keck

A mosaic of two 2k x 4k fully depleted, high resistivity CCD detectors was installed in the red channel of the Low Resolution Imaging Spectrograph for the Keck-I Telescope in June, 2009 replacing a monolithic Tektronix/SITe 2k x 2k CCD. These CCDs were fabricated at Lawrence Berkeley National Laboratory (LBNL) and packaged and characterized by UCO/Lick Observatory. Major goals of the detector upgrade were increased throughput and reduced interference fringing at wavelengths beyond 800 nm, as well as improvements in the maintainability and serviceability of the instrument. We report on the main features of the design, the results of optimizing detector performance during integration and testing, as well as the throughput, sensitivity and performance of the instrument as characterized during commissioning.

Progress toward high-performance reflective and anti-reflection coatings for astronomical optics

There is a continued need for efficient reflective and anti-reflection (AR) coatings for increasingly large optics in astronomy. The requirements for these coatings differ in several respects from those developed for commercial use. In general, they require a broad spectral coverage, high-efficiency, long life under semi-exposed conditions, and the ability to be removed without damage to expensive substrates. UCO/Lick Observatory has undertaken an effort to develop improved coatings for astronomical optics. In this paper, we report on progress toward (a) robust protected silver coatings for telescopes; (b) enhanced silver and aluminum coatings for instruments; and (c) hardened sol-gel AR coatings. Examples of some of our new coatings are in use at Lick and Keck Observatories. The problems involved in successful coatings are multifaceted and we summarize our major findings to date. This includes our requirements, test procedures, and performance and durability results for the three types of coatings mentioned.

DEIMOS: a wide-field faint-object spectrograph

This paper describes the design of DEIMOS -- a dual beam, off axis, multi object spectrograph of medium resolution, being designed for the Keck II telescope on Mauna Kea in Hawaii. The difficult and advanced scientific goals of the DEIMOS project have generated many challenging design requirements. The DEIMOS team at Lick Observatory has been responding to these challenges with new and unique concepts in instrument design and fabrication.

Chemical reactivity testing of optical fluids and materials in the DEIMOS spectrographic camera for the Keck II telescope

The DEIMOS Spectrograph Camera contains tow doublets and a triplet. Each group contains materials differing in thermal coefficient expansion, mechanical and optical properties. To mate the elements and at the same time accommodate large camera temperature changes, we will fill the space between with an optical fluid couplant. We selected candidate couplants, lens-support materials, and fluid-constraining materials based on published optical, mechanical and chemical properties. We then tested the chemical reactivity between the coupling fluids, lens-support and fluid- constraining materials. We describe here the test configurations, our criteria for reactivity, and the result for various test durations. We describe our conclusions and final choices for couplant and materials.

Design update of DEIMOS: a wide-field faint-object spectrograph

DEIMOS is a dual beam, off axis, multi object spectrograph of medium resolution being designed for the Keck II Telescope on Mauna Kea in Hawaii. The difficult an advanced scientific goals of the DEIMOS project have generated many challenging design requirements. The DEIMOS team at Lick Observatory has been responding to these challenges with new and unique concepts in instrument design and fabrication. This paper is an update to the paper presented at the SPIE conference in Landskrona, Sweden in 1996.

Assembly and testing of the ESI camera

The Echellette Spectrograph and Imager (ESI), currently being delivered for use at the Cassegrain focus of the Keck II telescope employs an all-spherical, 308 mm focal length f/1.07 Epps camera. The camera consists of 10 lens elements in 5 groups: an oil-coupled doublet; a singlet, an oil- coupled triplet; a grease-coupled triplet; and a field flattener, which also serves as the vacuum-dewar window. A sensitivity analysis suggested that mechanical manufacturing tolerances of order +/- 25 microns were appropriate. In this paper we discuss the sensitivity analysis, the assembly and the testing of this camera.

DEIMOS camera assembly

DEIMOS is a large multi-object spectrography with an imaging mode that is being built for the W. M. Keck 2 Telescope. The camera contains nine lens elements in five groups. The overall length of the camera and detector assembly is 0.67 meters, and the largest element is 0.33 meters in diameter. Typical centration and spacing tolerances are at the level of 25 microns. We describe the error budget, the design of the lens-supporting structure, and the assembly procedures.

Aspheric lens fabrication and testing at UCO/Lick Observatory

Aspherical surfaces on lenses are difficult to produce and test. There are many innovative approaches used today to address the complexities of this process. The size, quality, and quantity of the lens to be produced dictate the best approach. The UCO/Lick Observatory Optical Lab has fabricated aspheric lenses to diameters over 12 inches using fabrication and testing techniques developed specifically for high quality, one-of-a-kind lenses, with axi-symmetric profiles and significant departures from sphere. This paper describes the manufacturing procedures used at UCO/Lick to fabricate aspheric lenses typical for todays astronomical applications.