The new Gottingen Fabry-Perot spectrometer for two-dimensional observations of the Sun

Studies of small-scale dynamics and magnetic fields in the solar atmosphere require spectroscopy and polarimetry with high spatial resolution. For this purpose, spectrometers based on Fabry-Perot interferometers (FPIs) have advantages over slit spectrographs. They possess a high throughput and allow fast two-dimensional, narrow-band imaging and image reconstruction of the data. In the present contribution we describe an upgrade, essentially renewal, of the Gottingen FPI spectrometer achieved during the first half of 2005. A new etalon from IC Optical Systems Ltd. (formerly Queensgate), England, with 70 mm free aperture for high spectral resolution has been mounted. New CCD detectors from La Vision GmbH (Gottingen) with powerful computer hard-and software were implemented. We consider the product of signal-to-noise ratio, frame rate, and field of view as a measure of the efficiency. At low light levels, e. g. in narrow-band speckle applications, this product has increased by a factor similar to 60 compared to the old system. In addition, several spectral regions can now be scanned quasi-simultaneously. We present first results obtained with the upgraded spectrometer. The efforts are undertaken to provide an up-to-date post-focus instrument for the new German 1.5 m GREGOR solar telescope presently under construction at the Observatorio del Teide on Tenerife.