A semi-automated solar telescope designed for precise surface photometry measurements is headed for installation at Mauna Loa. This instrument will be operated in collaboration with the High Altitude Observatory. It will work in concert with identical telescopes at the Osservatorio Astronomico di Roma and the NSO Sacramento Peak Observatory to obtain measurements which will help us understand the origins of the eleven-year solar luminosity cycle. The accompanying photo shows a view of the Organ mountains and the White Sands Basin reflected against the 15 cm telescope objective, from the site at NSO/Sacramento Peak Observatory, where the telescope was developed, assembled, and tested.
The PSPT telescopes use a new 2K x 2K pixel CCD (Thomson) camera that was developed for this experiment. The camera allows very high photometric dynamic range measurements with rapid (8 million pixels/s) readout, low readout noise, and large well capacity pixels. An active tip/tilt mirror stabilizes the full-disk image, while continuous scintillation measurements provide a mechanism for frame-selecting data to provide the highest possible spatial resolution allowed by the observing site. Photometric measurements in three 0.25 to 0.5 nm bandwidth filters at CaII K, a blue and a red continuum wavelength are obtained with photometric accuracy of about 0.1%. In combination with satellite measurements of the total integrated sunlight, the PSPT photometric network will allow us to understand the physical mechanisms that cause magnetic fields at the solar photosphere to affect the solar irradiance and luminosity.
The Precision Solar Photometric Telescope (PSPT) Project is funded jointly by the NSF/ATM and AST divisions. The instruments are collaboratively operated by the PSPT partners (HAO and OAR). The instrument was developed by Roy Coulter (Instrument Specialist), Haosheng Lin (Instrument Scientist) and Jeff Kuhn (Project Scientist).