3 Description of Devasthal sites

Amongst the four sites mentioned above, Devasthal was chosen for further in depth study based on the criteria such as logistics, altitude, approachability and local topography conducive to good seeing. It is worth mentioning that there are no mountain ranges higher than Devasthal peak within an aerial radius of 1 km which can create turbulence and thus degrade the seeing. As the name Devasthal in Hindi language means place of God, there is an ancient Shiva (one of Hindu Gods) temple at the highest point of this region. The geographical and contour maps of Devasthal region are shown in Fig. 1. This site except for the last 3-4 km is connected to major towns (e.g. Nainital, Kathgodam and Haldwani) by a 6 m wide metalled road. It is far away from any urban development and therefore light contamination is virtually nil. Two potential sites for locating the modern optical telescope were identified. This selection is primarily based on logistics, not to disturb the location of the temple at Devasthal top, apart from being relatively free from trees. The two sites which are separated by about 1.5 km from each other are hereinafter referred as Site 1 and Site 2. Using a GPS clock unit accurate geographical coordinates of Devasthal Site 1 have been determined. The altitude is 2420 $\pm$ 5 m, while longitude and latitude are $79\hbox{$^\circ$ }$ 40' 57'' E $\pm$ 1 $^{\prime\prime}$ and $29\hbox{$^\circ$ }$ 22' 46'' N $\pm$ 1 $^{\prime\prime}$ respectively. It is about 1.5 km from the metalled road. Sufficient amount of water is available from natural springs near this site. Site 2 is close to Devasthal peak and is about 120 m higher than Site 1.

The theory of seeing along with the observations carried out at Devasthal are given in the following sections.