Max-Planck-Institut für extraterrestrische Physik

- Infrared/Submillimeter Astronomy -

The SHARP I camera

SHARP I mounted on the NTT

This Camera was designed to obtain diffraction-limited images in K-Band of the galactic center. Some of its technical details are given in the following table. Detector 256x256 Pixel NICMOS 3 Wavelength Coverage 1 µm - 2.5 µm Image Scale 50 mas per pixel Temperature liquid nitrogen (77 K) Exposure Time > 0.15 sec The camera was exclusively built to be mounted at the New Technology Telescope, which is located in La Silla, Chile and operated by the European Southern Observatory. Since 1992, the camera was used once a year to observe the Galactic Center and other astronomical targets.

This picture shows the optical system of our NIR Speckle-Camera SHARP I. Light comes in from the right through the window. The path is folded by the 4 prism reflectors. 12 different filters are mounted in the filter wheel: 3 broadband filters for the J (1.10 - 1.40 µm)-, H (1.45 - 1.85 µm)-, and K (1.95 - 2.45 µm) as well as narrowband-filters for line and continuum (Bracket-gamma; 2.188 µm, He I; 2.059 µm, CO absorption bandhead; 2.295 µm).

Additional optical devices

In order to make the most out of this camera, we constructed three additional optical devices which can be optionally mounted in front of the Dewar window:

1. A polarizer mounted on a rotatable table which is made of BaF₂ with a diameter of 25 mm. Its wire grid constant is 0.25 µm.
2. A lens which halfs the pixel scale of SHARP I to 25 mas per pixel.
3. A dual prism which results in K-Band spectra of 1" length with a spectral resolution of 35.