urn:nasa:pds:context:telescope:kpno-mcmath-pierce-solar.main_1m61 1.0 1.13.0.0 Product_Context 2020-07-28 1.0 Created from information at https://www.nso.edu/telescopes/legacy-telescopes-2/ and https://www.noao.edu/kpno/. urn:nasa:pds:context:facility:observatory.kpno-mcmath-pierce-solar telescope_to_facility urn:nasa:pds:context:instrument:kpno-mcmath-pierce-solar.main_1m61.vacuum-spectrograph telescope_to_instrument 1.61 111.595 31.9584 2096 A 1.61-meter (5 ft 3 in) primary mirror, reflecting telescope fed by 2.03-meter heliostat, unobstructed. The telescope uses the heliostat at the top of its main tower to direct the sun's light down a long shaft to the primary mirrors. The distinctive diagonal shaft continues underground, where the telescope's primary mirror is located. Tip-tilt correction and low order wavefront correction is available with a number of portable optical benches. These are primarily used with the Main spectrograph and the Solar Stellar spectrograph on the Main telescope, but due to their compact mounting they could be used with other telescopes and instruments in the facility. The third mirror of the main telescope which sends the light down into the observing room can be moved above three different positions. Two of these have a vacuum spectrograph beneath them, one of 18 meter deep and the other 4 meter deep with lower resolution but higher light throughput. These two spectrographs are able to rotate to compensate for the rotation of the image caused by the use of a heliostat. The third position can only be equipped with a static optical table with no image rotation correction and is therefore rarely used.