DFM's three 1.3m telescope observatories for TAOS II

Academia Sinica Institute of Astronomy and Astrophysics, Harvard Smithsonian CFA, and Universidad Nacional Autónoma de México (UNAM) contracted DFM Engineering to build three (3) 1.3-M aperture F/4 wide field optical telescopes for their Transneptunian Automated Occultation Survey  (TAOS II) project.  The telescopes are located at the Observatorio de San Pedro Mártir in Baja California, Mexico, approximately 100 miles South and 60 miles east of Ensenada, Mexico at an altitude of 9,000 ft.

Included in this project were three telescope enclosures. DFM Engineering has worked with many architects over the last 40 years and understands the limitations these architects bring to designing and building high-performance observatories.

Starting with a clean-slate, DFM Engineering has designed the ideal observatory building.  The design began with integrating proper mirror handling equipment to provide for safe and easy servicing of the telescope optics.  Not content with the performance of other observatories, DFM brought numerous design improvements to drastically improve the seeing ability of the telescope.

An often neglected aspect of observatory design is "dome seeing," a term encompassing how the design and construction of the dome (and the surrounding structure) affects the Delivered Image Quality (DIQ). During nighttime viewing, the outside air is usually cooler than any structures of significant mass. This causes the air inside the dome to be warmer than the ambient air temperature. When the dome shutter is opened, the warmer air in the dome vents out of the shutter, resulting in warm and cool air mixing and optical distortion.  Because of the shutter's limited area, this resulting air distortion is concentrated directly in the line-of-sight of the telescope.

To address optical turbulence, the DFM building design features low thermal mass about 1/4 that of a conventional observatory.  Thermal control is achieved through minimal internal heat generation, passive and powered ventilation, and a sun shade placed outside of the building main wall to minimize the day time heating of the observatory.  The top of the telescope support pier is also placed 40-ft (12.2-m) above ground to place the telescope above any optical turbulence caused by nearby trees.  Together, these features create the best “dome seeing” possible from modern observatories.