The design and on-sky results of the prototype of a low-resolution spectrograph for the thai national telescope

Abstract

The objectives of the research project presented in this paper are to design and develop a Low Resolution Spectrograph for the 2.4 m Thai National Telescope. The Low Resolution Spectrograph will deliver a spectrum in the spectral range (440-740 nm), with a resolution of R approximately equals to 1,000 at the central wavelength, λc, of 600 nm, while observing through a slit with a width of 0. 9 arcsecond wide (in long-slit mode) or during slit-less observations. The Low Resolution Spectrograph was designed to have a total weight of less than 20 kg and a maximum displacement due to gravity of less than 6 microns during a 360° rotation of the instrument cube. We have installed a prototype of the Low Resolution Spectrograph on the Thai National Telescope in December 2018. We have tested its performance on stellar objects during a one-night observing run. During these observations we calibrated the instrument using a Thorium-Argon spectral calibration lamp and a Tungsten lamp and recorded the spectrum of the planetary nebula NGC 2392 in both slit-less and long-slit modes. We measured a spectral resolution of 800-1,300 over the wavelength range 440-740nm, thus demonstrating that the on-sky performance of the prototype was in agreement with the theoretical specifications.