Solar Telescope
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A solar telescope is a special purpose telescope used to observe the Sun. Solar telescopes usually detect light with wavelengths in, or not far outside, the visible spectrum. Obsolete names for Sun telescopes include heliograph and photoheliograph.


Professional solar telescopes

Solar telescopes need optics large enough to achieve the best possible diffraction limit but less so for the associated light-collecting power of other astronomical telescopes. However, recently newer narrower filters and higher framerates have also driven solar telescopes towards photon-starved operations. Both the Daniel K. Inouye Solar Telescope as well as the proposed European Solar Telescope (EST) have larger apertures not only to increase the resolution, but also to increase the light-collecting power. Because solar telescopes operate during the day, seeing is generally worse than for night-time telescopes, because the ground around the telescope is heated which causes turbulence and degrades the resolution. To alleviate this, solar telescopes are usually built on towers and the structures are painted white. The
Dutch Open Telescope The Dutch Open Telescope (DOT) is an optical solar telescope located on Roque de los Muchachos Observatory, La Palma (near the Swedish Solar Telescope, Swedish 1-m Solar Telescope). With a main mirror of 45 centimeters, it can reach an 0.2 arcsecon ...
is built on an open framework to allow the wind to pass through the complete structure and provide cooling around the telescope's main mirror. Another solar telescope-specific problem is the heat generated by the tightly-focused sunlight. For this reason, a
heat stop In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...
is an integral part of the design of solar telescopes. For the Daniel K. Inouye Solar Telescope, the heat load is 2.5 MW/m2, with peak powers of 11.4 kW. The goal of such a heat stop is not only to survive this heat load, but also to remain cool enough not to induce any additional turbulence inside the telescope's dome. Professional solar observatories may have main optical elements with very long focal lengths (although not always,
Dutch Open Telescope The Dutch Open Telescope (DOT) is an optical solar telescope located on Roque de los Muchachos Observatory, La Palma (near the Swedish Solar Telescope, Swedish 1-m Solar Telescope). With a main mirror of 45 centimeters, it can reach an 0.2 arcsecon ...
) and light paths operating in a vacuum or
helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
to eliminate air motion due to convection inside the telescope. However, this is not possible for apertures over 1 meter, at which the pressure difference at the entrance window of the vacuum tube becomes too large. Therefore, the Daniel K. Inouye Solar Telescope and the EST have active cooling of the dome to minimize the temperature difference between the air inside and outside the telescope. Due to the suns narrow path across the sky, some solar telescopes are fixed in position (and are sometimes buried underground), with the only moving part being a heliostat to track the Sun. One example of this is the McMath-Pierce Solar Telescope.


Selected solar telescopes

* The
Einstein Tower The Einstein Tower (German: ''Einsteinturm'') is an astrophysical observatory in the Albert Einstein Science Park in Potsdam, Germany built by architect Erich Mendelsohn. It was built on the summit of the Potsdam '' Telegraphenberg'' to house a ...
(''Einsteinturm'') became operational in 1924 * McMath-Pierce Solar Telescope (1.6 m diameter, 1961–) * Andrei Severny Solar Telescope (90 cm diameter, 1954–) in
Crimea Crimea, crh, Къырым, Qırım, grc, Κιμμερία / Ταυρική, translit=Kimmería / Taurikḗ ( ) is a peninsula in Ukraine, on the northern coast of the Black Sea, that has been occupied by Russia since 2014. It has a p ...
*
Multi-purpose automated solar telescope Multi-purpose is something that has more than one purpose and may more specifically refer to: Buildings * Arena * Auditorium * Civic center * Coliseum * Convention center * Facility * Gymnasium, also called "Multi-Purpose Room" (MPR) * Mult ...
(80 cm diameter) in Republic of Buryatia, Russia *
Large solar vacuum telescope Large means of great size. Large may also refer to: Mathematics * Arbitrarily large, a phrase in mathematics * Large cardinal, a property of certain transfinite numbers * Large category, a category with a proper class of objects and morphisms ...
(76 cm diameter, 1980-) on the coast of lake Baikal, Russia * McMath-Hulbert Observatory (24"/61 cm diameter, 1941–1979) * Swedish Vacuum Solar Telescope (47.5 cm diameter, 1985–2000) * Swedish 1-m Solar Telescope (1 m diameter, 2002–) *
Richard B. Dunn Solar Telescope The Dunn Solar Telescope also known as the Richard B. Dunn Solar Telescope is a unique vertical-axis solar telescope, in Sunspot, New Mexico located at Sacramento Peak, New Mexico. It is the main telescope at the Sunspot Solar Observatory, operate ...
(0.76 m diameter, 1969–) * Mount Wilson Observatory *
Dutch Open Telescope The Dutch Open Telescope (DOT) is an optical solar telescope located on Roque de los Muchachos Observatory, La Palma (near the Swedish Solar Telescope, Swedish 1-m Solar Telescope). With a main mirror of 45 centimeters, it can reach an 0.2 arcsecon ...
(45 cm diameter, 1997–) * The Teide Observatory hosts multiple solar telescopes, including ** the 70 cm Vacuum Tower Telescope (1989–) and ** the 1.5 m GREGOR Solar Telescope (2012–]). * Goode Solar Telescope (1.6 m, 2009-) * Chinese Large Solar Telescope (CLST) (180 cm diameter, 2019–) * Daniel K. Inouye Solar Telescope (DKIST), a telescope with 4m aperture. * European Solar Telescope (EST), a proposed 4-meter class aperture telescope. *
Chinese Giant Solar Telescope The Chinese Giant Solar Telescope (CGST) is a proposed solar telescope in China. CGST will be an infrared and optical solar telescope. Its spatial resolution is equivalent to an 8 m-diameter telescope, and the light-gathering power equivalent t ...
(CGST), a proposed 5-8 meter aperture telescope. *
National Large Solar Telescope The National Large Solar Telescope (NLST) is a Gregorian multi-purpose open telescopeHasan, S. S. The Indian National Large Solar TelescopSolar and Stellar Variability: Impact on Earth and Planets, Proceedings of the International Astronomical ...
(NLST), is a Gregorian multi-purpose open telescope proposed to be built and installed in India and aims to study the Sun's microscopic structure.


Other types of observation

Most solar observatories observe optically at visible, UV, and near infrared wavelengths, but other solar phenomena can be observed — albeit not from the Earth's surface due to the absorption of the atmosphere: * Solar X-ray astronomy, observations of the Sun in x-rays * Multi-spectral solar telescope array ( MSSTA), a rocket launched payload of UV telescopes in the 1990s * Leoncito Astronomical Complex operated a submillimeter wavelength solar telescope. * The Radio Solar Telescope Network (RSTN) is a network of solar observatories maintained and operated by the U.S.
Air Force Weather Agency The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...
. *
CERN Axion Solar Telescope The CERN Axion Solar Telescope (CAST) is an experiment in astroparticle physics to search for axions originating from the Sun. The experiment, sited at CERN in Switzerland, was commissioned in 1999 and came online in 2002 with the first data ...
(CAST), looks for solar axions in the early 2000s


Amateur solar telescopes

In the field of amateur astronomy there are many methods used to observe the Sun. Amateurs use everything from simple systems to project the Sun on a piece of white paper, light blocking filters, Herschel wedges which redirect 95% of the light and heat away from the eyepiece, up to hydrogen-alpha filter systems and even home built spectrohelioscopes. In contrast to professional telescopes, amateur solar telescopes are usually much smaller. With a conventional telescope, an extremely dark filter at the opening of the primary tube is used to reduce the light of the sun to tolerable levels. Since the full available spectrum is observed, this is known as "white-light" viewing, and the opening filter is called a "white-light filter". The problem is that even reduced, the full spectrum of white light tends to obscure many of the specific features associated with solar activity, such as prominences and details of the chromosphere (i.e., the surface). Specialized solar telescopes facilitate clear observation of such H-alpha emissions by using a bandwidth filter implemented with a Fabry-Perot etalon.Morison, Ian (2016-12-25). H-alpha Solar Telescopes - An In-depth Discussion and Survey. Professor Morison's Astronomy Digest, 25 December 2016. Retrieved on 2020-04-17 from http://www.ianmorison.com/h-alpha-solar-telescopes-an-in-depth-discussion-and-survey/.


See also

*
List of solar telescopes This is a list of solar telescopes built in various countries around the world. A solar telescope is a specialized telescope that is used to observe the Sun. This list contains ground-based professional observatory telescopes at optical wavelength ...
* List of telescope types * Heliostat


References


External links

* *
CSIRO Solar Heliographpart 2

Solar Gallery of an amateur astronomer

Solar Gallery of the Hong Kong Astronomical Society
* {{Authority control Astronomical instruments Telescope