Solar telescope
Encyclopedia
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
used to observe the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. Solar telescopes usually detect light with wavelengths in, or not far outside, the visible spectrum
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm. In terms of...
.
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 European Solar TelescopeEuropean Solar Telescope
The European Solar Telescope is the European counterpart of the American Advanced Technology Solar Telescope which is currently being constructed in Hawaii. It is presently at the end of its conceptual design study...
as well as the Advanced Technology Solar Telescope
Advanced Technology Solar Telescope
The Advanced Technology Solar Telescope is a large domed solar telescope facility that is planned to be built by the National Solar Observatory atop the Haleakala volcano on the Pacific island of Maui. The site was selected for its clear daytime atmospheric seeing conditions, which will enable...
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
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...
and degrades the resolution. To alleviate this, solar telescopes are usually built on towers and the structures are painted white. The Dutch Open Telescope
Dutch Open Telescope
The Dutch Open Telescope , located on Roque de los Muchachos Observatory, La Palma , is an optical solar telescope with a main mirror of 45 centimeter and can reach an 0.2 arcsec resolution for sustained periods. For further optimization of the images, the DOT uses the image despeckle mechanism...
is built on an open framework to allow the wind to pass through the complete structure and provide cooling around the telescopes main mirror.
Another solar telescope-specific problem is the heat generated by the tightly-focused sunlight. For this reason, a heat stop is an integral part of the design of solar telescopes. For the upcoming ATST
Advanced Technology Solar Telescope
The Advanced Technology Solar Telescope is a large domed solar telescope facility that is planned to be built by the National Solar Observatory atop the Haleakala volcano on the Pacific island of Maui. The site was selected for its clear daytime atmospheric seeing conditions, which will enable...
, 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 length
Focal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus...
s (although not always, Dutch Open Telescope
Dutch Open Telescope
The Dutch Open Telescope , located on Roque de los Muchachos Observatory, La Palma , is an optical solar telescope with a main mirror of 45 centimeter and can reach an 0.2 arcsec resolution for sustained periods. For further optimization of the images, the DOT uses the image despeckle mechanism...
) and light paths operating in a vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
or helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
to eliminate air motion due to convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
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 EST
European Solar Telescope
The European Solar Telescope is the European counterpart of the American Advanced Technology Solar Telescope which is currently being constructed in Hawaii. It is presently at the end of its conceptual design study...
and ATST
Advanced Technology Solar Telescope
The Advanced Technology Solar Telescope is a large domed solar telescope facility that is planned to be built by the National Solar Observatory atop the Haleakala volcano on the Pacific island of Maui. The site was selected for its clear daytime atmospheric seeing conditions, which will enable...
have active cooling of the dome to minimize the temperature difference between the air inside and outside the telescope.
Because the Sun travels on a narrow fixed path across the sky, some solar telescopes are fixed in position (sometimes buried underground) with the only moving part being a heliostat
Heliostat
A heliostat is a device that includes a mirror, usually a plane mirror, which turns so as to keep reflecting sunlight toward a predetermined target, compensating for the sun's apparent motions in the sky. The target may be a physical object, distant from the heliostat, or a direction in space...
to track the Sun. One example of this being the McMath-Pierce Solar Telescope
McMath-Pierce Solar Telescope
The McMath-Pierce Solar Telescope is a 1.6-m f/54 reflecting solar telescope at Kitt Peak National Observatory in Arizona, USA. The building was designed by Myron Goldsmith and built in 1962. It is the largest telescope of its kind in the world and is named for astronomers Robert McMath and Keith...
.
Selected solar telescopes
See also List of solar telescopes- The Einstein TowerEinstein TowerThe Einstein Tower is an astrophysical observatory in the Albert Einstein Science Park in Potsdam, Germany built by Erich Mendelsohn. It was built on the summit of the Potsdam Telegraphenberg to house a solar telescope designed by the astronomer Erwin Finlay-Freundlich...
(Einsteinturm) became operational in 1924 - McMath-Pierce Solar TelescopeMcMath-Pierce Solar TelescopeThe McMath-Pierce Solar Telescope is a 1.6-m f/54 reflecting solar telescope at Kitt Peak National Observatory in Arizona, USA. The building was designed by Myron Goldsmith and built in 1962. It is the largest telescope of its kind in the world and is named for astronomers Robert McMath and Keith...
(1.6 m diameter, 1961–) - McMath-Hulbert ObservatoryMcMath-Hulbert ObservatoryThe McMath-Hulbert Solar Observatory is a decommissioned solar observatory in Lake Angelus, Michigan, USA. It was established in 1929 as a private observatory by father and son Francis Charles McMath and Robert Raynolds McMath and their friend, Judge Henry Hulbert...
(24"/61 cm diameter, 1941–1979) - Swedish Vacuum Solar TelescopeSwedish Vacuum Solar TelescopeThe Swedish Vacuum Solar Telescope was a 47.5 cm solar telescope on La Palma in the Canary Islands. It was removed on 28 August 2000, and has been superseded by the Swedish 1-m Solar Telescope....
(47.5 cm diameter, 1985–2000) - Swedish 1-m Solar TelescopeSwedish Solar TelescopeThe Swedish 1-m Solar Telescope is a refracting solar telescope at Roque de los Muchachos Observatory, La Palma in the Canary Islands. It is run by the Institute for Solar Physics of the Royal Swedish Academy of Sciences. The primary element is a single fused silica lens, making it the second...
(1 m diameter, 2002–) - Richard B. Dunn Solar Telescope (1.63 m diameter, 1969–)
- Mount Wilson ObservatoryMount Wilson ObservatoryThe Mount Wilson Observatory is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson, a 5,715 foot peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles...
- Dutch Open TelescopeDutch Open TelescopeThe Dutch Open Telescope , located on Roque de los Muchachos Observatory, La Palma , is an optical solar telescope with a main mirror of 45 centimeter and can reach an 0.2 arcsec resolution for sustained periods. For further optimization of the images, the DOT uses the image despeckle mechanism...
(45 cm diameter, 1997–) - The Teide ObservatoryTeide ObservatoryThe Observatorio del Teide is an astronomical observatory on Tenerife operated by the Instituto de Astrofísica de Canarias. Opened in 1964, it became one of the first major international observatories, attracting telescopes from different countries around the world because of the good astronomical...
hosts multiple solar telescopes, including- the 70 cm Vacuum Tower TelescopeVacuum Tower TelescopeFor the vacuum tower telescope at Sacramento Peak, see Richard B. Dunn Solar Telescope.The Vacuum Tower Telescope is an evacuated-optics solar telescope located at the Teide Observatory on Tenerife in the Canary Islands. It is operated by the Kiepenheuer-Institut für Sonnenphysik ..It has a ...
(1989–) and - the 1.5 m GREGOR solar telescope nearing completion .
- the 70 cm Vacuum Tower Telescope
- Advanced Technology Solar TelescopeAdvanced Technology Solar TelescopeThe Advanced Technology Solar Telescope is a large domed solar telescope facility that is planned to be built by the National Solar Observatory atop the Haleakala volcano on the Pacific island of Maui. The site was selected for its clear daytime atmospheric seeing conditions, which will enable...
, a planned telescope with 4m aperture.http://atst.nso.edu/
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 (MSSTAMSSTAThe Multi-spectral solar telescope array, or MSSTA, was a sounding rocket payload built by Professor A.B.C. Walker, Jr. at Stanford University in the 1990s to test EUV/XUV imaging of the Sun using normal incidence EUV-reflective multilayer optics...
), a rocket launched payload of UV telecopes in the 1990s - Leoncito Astronomical ComplexLeoncito Astronomical ComplexThe Leoncito Astronomical Complex is an astronomical observatory in the San Juan Province of Argentina. The Leoncito Astronomical Complex is one of two observatories located within El Leoncito National Park, located in an area of the country which rarely sees cloud cover. The other facility is the...
operated a submillimeter wavelength solar telescope. - The Radio Solar Telescope NetworkRadio Solar Telescope NetworkThe Radio Solar Telescope Network is a network of solar observatories maintained and operated by the U.S.Air Force Weather Agency. The RSTN consists of ground-based observatories in Australia, Italy, Massachusetts, New Mexico and Hawaii.- History :...
(RSTN) is a network of solar observatories maintained and operated by the U.S.Air Force Weather AgencyAir Force Weather AgencyThe Air Force Weather Agency is a Field Operating Agency and the lead military meteorology center of the United States Air Force...
. - CERN Axion Solar Telescope(CAST), looks for solar axions in the early 2000s
Amateur solar telescopes
Amateur astronomy
Amateur astronomy, also called backyard astronomy and stargazing, is a hobby whose participants enjoy watching the night sky , and the plethora of objects found in it, mainly with portable telescopes and binoculars...
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
Herschel Wedge
A Herschel Wedge or Herschel prism is an optical prism used in solar observation to refract most of the light out of the optical path, allowing safe visual observation.-Overview:...
which redirect 95% of the light away from the eyepiece, up to hydrogen-alpha filter systems and even home built spectrohelioscope
Spectrohelioscope
A spectrohelioscope is a type of solar telescope designed by George Ellery Hale in 1924 to allow the Sun to be viewed in a selected wavelength of light...
s. In contrast to professional telescopes, amateur solar telescopes are usually much smaller.
External links
- Solar telescopes, ScholarpediaScholarpediaScholarpedia is an English-language online wiki-based encyclopedia that uses the same MediaWiki software as Wikipedia, but has features more commonly associated with open-access online academic journals....
- CSIRO Solar Heliograph part 2
- Solar Gallery of an amateur astronomer
- Solar Gallery of the Hong Kong Astronomical Society