Abstract:
The 3.6-meter Indo–Belgian Devasthal optical telescope (DOT) has been used for optical and near-infrared (NIR) observations of celestial objects. The telescope has detected stars of B=24.5±0.2,R=24.6±0.12 and g=25.2±0.2 mag in exposure times of 1200, 4320 and 3600 s respectively. In one hour of exposure time, a distant galaxy of 24.3 ± 0.2 mag and point sources of ∼25 mag have been detected in the SDSS i band. The NIR observations show that stars up to J=20±0.1,H=18.8±0.1 and K=18.2±0.1 mag can be detected in effective exposure times of 500, 550 and 1000 s respectively. The nbL band sources brighter than ∼9.2 mag and strong (≥0.4 Jy) PAH emitting sources like Sh 2-61 can also be observed with the 3.6-meter DOT. A binary star with angular separation of 0.′′4 has been resolved by the telescope. Sky images with sub-arcsec angular resolutions are observed with the telescope at wavelengths ranging from optical to NIR for a good fraction of observing time. The on-site performance of the telescope is found to be at par with the performance of other, similar telescopes located elsewhere in the world. Owing to the advantage of its geographical location, the 3.6-meter DOT can provide optical and NIR observations for a number of frontline galactic and extra-galactic astrophysical research problems, including optical follow-up of GMRT and AstroSat sources and optical transient objects.
