Multi-wavelength Simultaneous High throughput Imager and polarimeter (MuSaSHI) : development and its performance

摘要

We describe a development and performance evaluations for Multi-wavelength Simultaneous High throughput Imager and polarimeter called as "MuSaSHI". The science drivers arc high-precision muticolor photometric studies of time-variable astronomical phenomena such as variable stars, transiting planets and asteroids. MuSaSHI is designed to be mounted on the SaCRA telescope at Saitama University, dedicated for relatively wide field imaging and polarimetry in the three optical bands (r: 550 to 680 nm, i: 700 to 810 nm, z: 820 to 1000 nm) . The instrument is equipped with three Back-Illuminated thinned c2v CCDs which provide simultaneous r,i,z images having a field of view of 12.8 x 12.4 arcmin with a pixel scale of 0.73 arcsec. The optical system of MuSaSHI is composed of only two dichroic mirrors and three bandpass filters without lens, so that the total throughput is high especially at z band (~ 50%). In addition, the optics of MuSaSHI is designed for fast telescopes (F ~ 6.5) and with portability in mind so that it is able to be mounted on a larger aperture telescope with slower beam. The limiting magnitudes with 60 sec integration (10σ) are r_(lim) = 16.8, i_(lim) = 17.1, and z_(lim)= 17.2 mag. We demonstrate relative photometric precisions of ＜0.1 % in the all bands for a K0 V star WASP-84 which hosts a transiting planet with 30s exposure observations.