Richard B. Dunn Solar Telescope

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Richard B. Dunn Solar Telescope
The Dunn Solar Telescope in Sunspot, New Mexico.
Organization	National Solar Observatory
Location	Sacramento Peak, New Mexico
Wavelength	310–1000 nm (optical, IR)
Built	1958–1969
Telescope style	Prime focus
Diameter	60 in, 152.4 cm
Angular resolution	0.33 mas/nm (0.1–0.33 arcsecond)
Collecting area	4.9 ft², 0.456 m² (30 inch entrance window)
Focal length	180 ft, 54.86 m
Mounting	Vertical axis with heliostat
Dome	None; enclosed vacuum optics
Website	http://nsosp.nso.edu/dst/

The Dunn Solar Telescope (officially the Richard B. Dunn Solar Telescope) is a unique vertical-axis solar telescope, located at the National Solar Observatory at Sacramento Peak, New Mexico. The optical path starts at a heliostat on top of a 136 foot (41.5 m) tall tower and continues 193 feet (58.8 m) more underground to the primary mirror.[1] It then returns to one of six quartz optical windows in the floor of an optical laboratory at ground level. The optics are evacuated to eliminate distortion due to convection in the telescope that would otherwise be caused by the great heat produced by focusing the light of the sun.

A unique feature of the telescope is its approach to image derotation: the entire 100 m long telescope and 40-foot diameter optics lab, 250 tons total, rotates suspended from a mercury float bearing at the top of the tower.

Originally the Vacuum Tower Telescope at Sacramento Peak, it was renamed in 1998[2] in honor of the retiring solar astronomer Richard B. Dunn (de:Richard B. Dunn) who was the driving force behind its construction.[3] The lowest excavated point (the bottom of the sump) is 228 feet (69.5 m) below ground.