Speaker
Description
The Two-Channel-Focal-Reducer Rozhen (FoReRo2) was delivered to the Bulgarian National Astronomical Observatory (BNAO) Rozhen based on a contract between the Max-Planck Institute for Solar System Research and the Institute of Astronomy and National Astronomical Observatory (IA and NAO) in 2004. Since then, the FoReRo2 has been used at the f/8 Ritchey-Chrétien focus of the 2m Ritchey-Chrétien-Coudé telescope, where it reduces the original focal ratio to f/2.8, corresponding to an effective focal length of 5.6 m. The FoReRo2 is a multimode instrument offering a wide variety of observing capabilities: broadband and narrowband filter imaging; long slit low dispersion spectroscopy; Fabry-Pérot interferometry; imaging polarimetry; low dispersion spectropolarimetry. The two lenses of the blue and red channels are both colour-corrected in the range of 587-1014 nm and 365-436 nm, respectively.
One important improvement of the polarimetric mode is a new Wollaston prism. It is placed before the colour divider, and it feeds both channels simultaneously. The split angle of 0.71 degrees guarantees separation without overlapping the ordinary and extraordinary stripes projected on the blue and red CCDs. Combining the Wollaston prism and the available Grism for spectroscopic observations opens the way for carrying out low-dispersion spectropolarimetry.
In 2018, both channels of the FoReRo2 were equipped with new Andor CCD cameras iKon-L 9363, with the new dual antireflection deep depletion ‘BEX2-DD’ chip.
In February 2014, in the framework of the agreement for collaborative research actions between Armagh Observatory (AO) and IA and NAO, AO delivered to BNAO a half-waveplate (HWP) for joint polarimetric observations. This allows us to easily apply the beam-swapping technique (BST) described by Bagnulo et al. 2009 which is used to minimise instrumental polarisation introduced by the optical components located between the HWP and the CCDs.
We will present some results of small solar system bodies’ polarimetric observations to show the polarimetric capabilities of the FoReRo2 instrument, which we believe is invaluable for obtaining polarimetric observations of NEOs not only as one of a few instruments in the part of the world but also in general.
