OMEGA CASS - Introduction

The new IR Spectrometer and Array Camera for Calar Alto.

In addition to the IR-camera Omega-Prime, which offers a fixed scale of 0.4 arcsec per pixel at the prime focus of the 3.5 m telescope on Calar Alto, we have started to develop an infrared Camera for the 3.5m-Cassegrain focus, which will be specialized in high spatial resolution. This new camera is equipped with a 1024 x 1024 pixel array, as well, and makes use of the adaptive optics system Alfa, which provides diffraction limited resolution in combination with a laser guide star. In addition, Omega-Cass provides a true cryogenic re-imaging system which is not available at Omega-Prime. This offers the possibility to do low or even medium resolution long slit spectroscopy up to a resolution power of about 6000 all over the near infrared region and to use Wollaston prisms for high sensitive polarimetry of compact sources.

A real telescope focus is available at cryogenic temperatures, field limiting masks, slits or coronagraphic masks can be inserted. Even though a very preliminary layout of Omega-Cass is shown here, the optics has been designed in detail already. Three imaging scales of 0.3, 0.2 and 0.1 arcsec per pixel are realized using the f/10. In combination with the f/45 this yields image scales of 67, 44 and 22 mas/pixel. At present we plan to implement two filter wheels each of which will offer 12 positions, thus in total 22 filters canbe mounted in Omega Cass. An analyzer wheel will offer four grism positions, four Lyot stops, two Wollaston prisms and three wire-grid analyzer.