A. Omar

ARIES, Nainital, INDIA

AO related efforts at Devasthal site

Devasthal site

Longitude = 79.7 E Latitude = 29.4 N Altitude = 2450 meters above MSL Median seeing = 1”.1 Best seeing = 0”.6 Humidity = nominal 30 % (Winter)

down to 5% (in 2010-11)

Identified in early 2000 as a good site for large optical telescopes in the country. The site has an advantage that light pollution is very low, has not increased much since the past 10 years (21.2 mag/arcsec2 in V band) Due to its altitude, site is well above the first atmospheric boundary layer and extinction is low (0.06 mag in R and 0.22 mag in B band). The site has a 130-cm telescope installed in 2010. A 360-cm telescope and a 400-cm liquid mirror telescope will be installed by 2013. The institute also has active research in atmospheric science and operates a high power LIDAR at Manora Peak (20 km away).

Median Visual Seeing = 1”.1 Mean Seeing = 1”.2 (+/-0”.3) Best Seeing = 0”.6 Almost 40% of the nights seeing is below 1”.0

Sagar et al. (2000)

Wind speed (Median) ~ 2 m/s

Sagar et al. (2000)

The 130-cm Telescope (from DFM Eng. Inc. USA) Installed in 2010-11. F/4 Optics with corrector FoV = 66’ Full adjustment of M2 focus/tilt for optics alignment. Optics can produce ~0”.4 FWHM images. Roll of roof enclosure. Detection sensitivity ~ 20 mag star in 1 min in V/R bands

First images from 130-cm telescope

The 360-cm Telescope (from AMOS, Belgium)

Expected to be installed in 2013. Factory test phase beginning August 2011 until March 2012. The f/9 optics producing images with 50% energy within 0”.3 diameter. Raw plate scale 0”.064 in 10 micron. Active optics support for M1. Full control of M2 motions for optics alignment.

Why Adaptive Optics or high angular resolution imaging efforts at Devasthal?

1. Atmospheric conditions (low wind speed), low humidity (for NIR observations), and good seeing, and dark sky favour to carry out high angular resolution imaging from Devasthal telescopes. 2. The availability of largest apertures 360-cm and 400-cm in near future provides an excellent and unique test-bed for doing AO in the country. 3. Fried’s parameter r0 ~ 20 cm at 1.0 micron wavelength at Devasthal. At low wind speed (~1 m/s),The WFS/DM can operate at 10-15 Hz frequency at 1.0 um. For 0.5 micron wave-length r0~10 cm and DM needs to be operated at >35 Hz. (This is technologically feasible). 4. There is also an active program for atmosphere characterization in Nainital – synergy with the atmospheric science expertise. [Unique in the country]

D/r0 ~ 13 at 0.5um, – [Coherence time ~ 30 ms] Need to see how much improvement in angular resolution results with tip-tilt correction and speckle imaging. D/r0 ~ 6 at 1.0 um for 130-cm telescope - Can tip-tilt correction alone improves the Image quality significantly ? Starting this winter, first efforts will be made to carry out lucky imaging and speckle imaging experiments with 130-cm telescope. Two high speed EMCCD cameras (ANDOR iXon and Luca) capable of sampling images at <10 ms intervals will be employed in r’I’z’ filters. Also SBIG AO-8 unit will be used to test imaging.

Plans with 130-cm telescope (this winter)

Practicalities for AO development at ARIES

First priority in coming 2 years is successful operation of the 3.6 meter telescope at the site and its back end instruments. Not much dedicated manpower/ facility available at present for AO. Due to aperture advantage, low level efforts, experiments to be initiated with limited manpower on full AO and tip/tilt alone corrections. The 130-cm telescope to be used as test bed and emphasis on characterizing atmosphere over Devasthal for the next 2 years. Science program requires improvement in seeing – If images at ~0”.5 over 2’-3’ FoV can be obtained for about 60 nights in a year. May be only ground layer seeing correction, tip tilt alone or higher order alone? In the meantime learning from other experiments in the country (RoboAO etc.)

Plans for 360-cm Telescope

D/r0 ~ 36 at 0.5um and ~12 at 1.0 um; It will be interesting to carry out lucky imaging experiments with this aperture. The speckle imaging should yield a better result as the number of speckles will be quite large (~400 or more) and spatial sampling (0.06” in 10 um pixels) will be adequate. Set up an experimental test-bench for AO using MEMS in the laboratory. In long term, establish a closed loop AO using LGS with 3.6 meter telescope.

Resource Developments: 1. Systems & Control Engineering, IIT Mumbai (for system control development) 2. ESO – Chile (Dr. Rengaswamy) for speckle imaging experiments using bi-spectrum based inversion. 3. Also some communications with Nick Law for Lucky imaging. 4. Some ongoing communications with Univ. of Victoria, Canada and Caltech.

Anybody willing to use the existing 1.3 meter aperture or upcoming 3.6 meter aperture at Devasthal site for high angular resolution/ AO experiments is welcome.

Thanks