Instrumentation Overview

The Fairchild CCD

In partnership with Fairchild Imaging, MIRA uses the Peregrine 447 CCD camera as the primary CCD for imaging and some spectroscopic instruments. This camera uses the Fairchild back-illuminated 2K x 2K 15-micron 447 CCD. Because of its large size and excellent perfomance, this instrument has become the primary direct imaging camera. It was used for observations of the NASA Deep Impact event (Walker et al., Icarus 187, 285, 2007) and is currently being used for establishing the photometric standards for gravitational lens fields and studies of star formation regions. Fairchild CCDs and their cameras are described here.

Direct Imaging

The focal plane of the MIRA 36-inch telescope has a scale of 22 arc seconds/mm. A probe autoguider is used for guiding. Back-illuminated CCD cameras currently configured for direct imaging include a Finger Lakes 1K x 1K SITe 24-micron pixel CCD, a Apogee 47p with a e2v 1K x 1K, and a Fairchild Peregrine 447 2K x 2K. A front-illuminated 2K x 2K 9-micron early Kodak CCD in an Axiom camera is also available. A standard UBVRI filter set is used with the cameras as well as H-alpha and red-continuum filters.

Spectroscopy

The Cassegrain spectrograph supports two independent grating/camera combinations with their own CCDs. The low-resolution side currently uses a commercial 110-mm focal length lens and a PixelVision CCD camera employing a SITe 1024 x 600 back-illuminated CCD. The high-resolution side employs a 400mm custom UV-IR lens system in front of an Andor camera with a 1K x 256 26-micron e2v chip. A large variety of gratings are available permitting resolutions from 116 to 3600 on the low-resolution side and 420 to 13,000 on the high resolution side. This range can be extended to 58 - 20,000 using alternative camera optics.

Currently a high-resolution echelle spectrograph (MIRA Echelle: Mechelle) is under development. This fiber-fed sepctrograph wil lhave resolutions ranging from 20,000 to 80,000 and a wavelength coverage from 3100Å to 9950Å. The camera will use a back-illuminated Fairchild 4K x 4K CCD in a Spectral Instruments camera.

mechelle

The Telescope

MIRA's 36-inch telescope was designed by Frank Melsheimer and built by Frank Melsheimer, Tom Melsheimer, and Bruce Weaver. It was the first telescope of its size to be built with a roller drive instead of a primary worm gear. The primary mirror, figured to 1/37th of a wavelength of visible light, was the backup mirror to Project Stratoscope at Princeton University. Dr. Martin Schwarzschild arranged for the transfer of the mirror from Princeton and NASA to MIRA.

The mirror, the first mirror this size made of fused silica, was solid when delivered. It was cored at the University of Arizona Optical Sciences Center by Dr. Frank Melsheimer. The telescope was completed and moved to a temporary site in the Cachagua Valley in 1979. The Cachagua site, although poor for observational astronomy, was useful for engineering purposes and the development of the initial instrumentation.