[ ESO ] La Silla

La Silla - Science Operation Department
EFOSC2 Instrument Overview

General Characteristics and Observing Modes:

EFOSC2 is a focal reducer multi-mode instrument using multi-layer coated all-transmission optics. It is part-time mounted on the 3.6m telescope. The wavelength range of operation is between 305nm and 1100nm. The field of view is 5.2'x5.2'.

The following observing modes are available:

EFOSC2 observing modes:
IMA imaging
MOS multi-object spectroscopy (masks)
LSS longslit spectroscopy
IPOL imaging polarimetry (linear polarisation)
SPOL spectropolarimetry
PMOS multi-object spectropolarimetry
COR coronography

The 3.6m telescope is equipped with a differential tracking and guiding mode, so all of the observing modes above can in principle be used on moving targets as well.

Instrument Optics:

The main instrument optics consists of The camera is opened to F/4.9 with a focal length of 200mm. The 3.6m plate scale is 7".12/mm, therefore the focal plane scale of EFOSC2 is 11".75/mm, since the telescope is F/8.09.


The CCD#40 is a Loral/Lesser, thinned, AR coated, UV flooded, MPP chip controlled by ESO-FIERA. It's size is 2048 x 2048 pixel, the pixel size being 15mux15mu, or 0.157"x0.157" on the sky. The 2x2 binned pixels of the default CCD readout modes will be projected to 0".31 on the sky.

Four readout modes are offered for scientific purpose:

The fast mode is not characterised and only used for tests and acquisitions.

For more detailed information, please consult the detailed EFOSC2 webpages or the EFOSC2 manual.

Publications based on data obtained with the EFOSC2 instrument should quote the following reference paper: Buzzoni et al. 1984, ESO Messenger 38, 9
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