Astrophysics

Boller & Chivens Spectrograph at OAGH

Overview

The Boller & Chivens Spectrograph is a tool to obtain long-slit spectra of low and intermediate resolution through the use of different diffraction gratings as a disperser.

 The layout of a typical Boller & Chivens spectrograph is shown below.

The spectrograph is mounted at the f/12 Cassegrain focus of the telescope, and is equipped with a collimator of focal length 1080 mm and a camera of focal length 465 mm. At the image scale of 8.185''/mm, this amounts to approximately 0.463''/pix  along the spatial direction for the TK1024 CCD as the detector. Slit width can be changed manually at steps of 1 micron all the way up to 1000 microns. A typical slit width of 250 micron (or 2 arcsec) corresponds to 4 detector pixels. Maximum slit length allowed is around 3 arcmin. The spectrograph uses a reflection grating, whose orientation can be changed with a micrometer at steps of 5 arcmin. A HeAr lamp is available with the spectrograph for wavelength calibration. In the default mounting of the spectrograph the slit is oriented along east-west. This corresponds to a reading of 263 degrees on the scale of the mounting panel (well, there is more than one way of mounting and unfortunately it is not mounted always the same way). For any other slit orientation the entire panel needs to be rotated.