  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 seconds 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 seconds 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 having
angular separation of 0.4 arc-sec has been resolved by the telescope. Sky
images with sub-arc-sec 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. Due to
advantage of its geographical location, the 3.6 meter DOT can provide optical
and NIR observations for a number of front line Galactic and extra-galactic
astrophysical research problems including optical follow up of GMRT and
AstroSat sources and optical transient objects.
