First Light Preparations of the 4 m ILMT

Abstract

The 4 m International Liquid Mirror Telescope (ILMT) is a zenith-pointing optical observing facility at ARIES Devasthal observatory (Uttarakhand, India). The ¯rst light preparatory activities of the ILMT were accomplished in April 2022 followed by on-sky tests that were carried out at the beginning of May 2022. This telescope will perform a multi-band optical (SDSS g0 , r0 and i0 ) imaging of a narrow strip ( 220 ) of sky utilizing the time-delayed integration technique. Single-scan ILMT images have an integration time of 102 s and consecutive-night images can be co-added to further improve the signal-to-noise ratio. An image subtraction technique will also be applied to the nightly recorded observations in order to detect transients, objects exhibiting variations in °ux or position. Presently, the facility is in the commissioning phase and regular operation will commence in March 2023. This paper presents a discussion of the main preparation activities before ¯rst light, along with preliminary results obtained.