1-31 August 2023
Asia/Bangkok timezone

TNT Site and Observation Planning

The Thai 2.4-m National Telescope (TNT) is located at Doi Inthanon. The geographical coordinates are 18° 34´ 25.41” N, 98° 28´ 56.06” E, and the elevation is 2457 meters msl. Together with other smaller telescopes, they form the Thai National Observatory (TNO). The telescope is an alt-az with a 2.4m primary mirror[1]and two f/10 Nasmyth foci. At present, only one of these is equipped with a derotator. Nasmyth 1 hosts an instrument cube which can mount up to 4 instruments simultaneously and allows fast (less than one minute) switching between them. An autoguider exists but due to severe vignetting, it is normally not mounted on the cube. Without the autoguider, the current tracking performance is about one arcsecond over 15 minutes, depending on elevation.

The TNO site has a distinctive tall telecommunications tower to the East of the telescope, which blocks observations in a restricted area of the sky. Observers might consult the observing horizon map while preparing their observations.

Observers are also advised to check carefully the visibility of their targets depending on coordinates and time of the year, i.e. using a tool such as Staralt, which already includes the TNO site. The telescope can point to very low elevations, however, starting from about 30 degrees elevation the dome introduces some vignetting.

For more details see http://www.narit.or.th/index.php/en-observing-facilities/en-tno

[1]The primary is currently masked to 2.3m clear aperture, to avoid diffraction from the mirror edge.