Hubbry Logo
Solar telescopeSolar telescopeMain
Open search
Solar telescope
Community hub
Solar telescope
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Contribute something
Solar telescope
Solar telescope
Solar telescope
View on Wikipedia
from Wikipedia
The Swedish Solar Telescope at Roque de los Muchachos Observatory, La Palma in the Canary Islands

A solar telescope or a solar observatory 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

[edit]
McMath–Pierce solar telescope observing room

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.[1] 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 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 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.[2] 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) and light paths operating in a vacuum or helium 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 Sun's 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.

The Sun, being the closest star to earth, allows a unique chance to study stellar physics with high-resolution. It was, until the 1990s,[3] the only star whose surface had been resolved. General topics that interest a solar astronomer are its 11-year periodicity (i.e., the Solar Cycle), sunspots, magnetic field activity (see solar dynamo), solar flares, coronal mass ejections, differential rotation, and plasma physics.

Other types of observation

[edit]

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:

Amateur

[edit]
Public event organized to observe the Sun with solar telescope and solar glasses
Diagram of a Herschel Wedge and other solar viewing methods

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,[4] up to hydrogen-alpha filter systems and even home built spectrohelioscopes. In contrast to professional telescopes, amateur solar telescopes are usually much smaller.[citation needed]

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. Specialized solar telescopes facilitate clear observation of such H-alpha emissions by using a bandwidth filter implemented with a Fabry-Perot etalon.[5]

Solar tower

[edit]

A solar tower is a structure used to support equipment for studying the Sun, and is typically part of solar telescope designs. Solar tower observatories are also called vacuum tower telescopes. Solar towers are used to raise the observation equipment above atmospheric turbulence caused by solar heating of the ground and the radiation of the heat into the atmosphere. Traditional observatories do not have to be placed high above ground level, as they do most of their observation at night, when ground radiation is at a minimum.

The horizontal Snow solar observatory was built on Mount Wilson in 1904. It was soon found that heat radiation was disrupting observations. Almost as soon as the Snow Observatory opened, plans were started for a 60-foot-tall (18 m) tower that opened in 1908 followed by a 150-foot (46 m) tower in 1912. The 60-foot tower is currently used to study helioseismology, while the 150-foot tower is active in UCLA's Solar Cycle Program.

The term has also been used to refer to other structures used for experimental purposes, such as the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE), which is being used to study Cherenkov radiation, and the Weizmann Institute solar power tower.

Other solar telescopes that have solar towers are Richard B. Dunn Solar Telescope, Solar Observatory Tower Meudon and others.

Selected heliophysics missions

[edit]
See also: List of heliophysics missions

Selected solar telescopes

[edit]
See also: List of solar telescopes
Daocheng Solar Radio Telescope in China

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Solar telescope

View on Grokipedia
from Grokipedia
A solar telescope is a specialized designed exclusively for observing the Sun, distinguished from conventional astronomical telescopes by its adaptations to manage the overwhelming brightness, heat, and proximity of our star, enabling detailed study of without distortion from atmospheric or thermal gradients. These telescopes typically incorporate a —a tracking mirror system that redirects into a fixed —often along a tall tower structure to achieve exceptionally long focal lengths, sometimes exceeding 100 meters, which magnifies solar features for high-resolution imaging. To counteract image blurring caused by air heated by concentrated , many employ vacuum tubes or evacuated enclosures that eliminate convective currents, while others use temperature-controlled or helium-filled chambers for similar effects. Additional features include narrowband filters to isolate specific wavelengths, for real-time atmospheric correction, and off-axis designs to minimize scattered light, all supporting observations across the visible, , and spectra. The primary purpose of solar telescopes is to investigate the Sun's dynamic processes, including sunspots, magnetic fields, flares, prominences, and coronal mass ejections, which drive space weather and influence Earth's magnetosphere, ionosphere, and climate. By resolving features as small as 50 kilometers across the solar disk—equivalent to structures the size of a U.S. state—they facilitate measurements of solar magnetic activity, plasma flows, and energy transport, contributing to models of stellar evolution and predictions of solar-terrestrial interactions. Solar telescopes trace their origins to the early 20th century, when astronomer constructed pioneering instruments like the 1904 Snow Solar Telescope at , followed by larger tower designs such as the 60-foot (1908) and 150-foot (1912) solar towers there, which introduced vertical configurations to leverage stable air at altitude. Mid-century advancements included vacuum tower telescopes, exemplified by the Richard B. Dunn Solar Telescope (dedicated 1969) at Sacramento Peak, which used an underground vacuum path for unprecedented clarity. The McMath-Pierce Solar Telescope (1962) at became the world's largest at the time with its 1.6-meter , emphasizing spectroscopic studies. Modern milestones feature the 1-meter Swedish 1-m Solar Telescope (2002) and the 4-meter (2021) on , , which holds the record for the largest solar aperture and delivers diffraction-limited views resolving features down to 20 kilometers. Ongoing developments emphasize larger apertures, advanced instrumentation like spectro-polarimeters, and integration with space-based observatories such as NASA's , enhancing our understanding of the Sun's role in the and beyond.

Introduction and History

Definition and Purpose

A solar telescope is a specialized designed exclusively for observing the Sun, typically operating in visible, , or wavelengths to study without damaging equipment or observers. Unlike general astronomical telescopes, which observe faint night-sky objects, solar telescopes are engineered to capture high-resolution images and spectra of the Sun's dynamic features. The use of telescopes for dates back to the , when early instruments first recorded sunspots. The primary purpose of solar telescopes is to enable detailed imaging and spectroscopy of the solar surface, known as the , as well as the overlying atmosphere, including the and corona, along with the Sun's magnetic fields. These capabilities are essential for research, which investigates solar activity, events, and solar-terrestrial interactions that influence Earth's environment. By providing unprecedented views of solar processes, such telescopes support predictions of phenomena that affect operations, power infrastructure, and global communications. Solar telescopes face unique challenges due to the Sun's extremely intense brightness and heat, which can overwhelm standard optical systems and pose risks to both instruments and human observers. To address this, they incorporate narrowband filters, such as those tuned to the (H-alpha) or calcium-K spectral lines, which isolate specific wavelengths to reduce light intensity while highlighting key solar features like prominences and flares. Advanced heat rejection mechanisms, including cooling systems and off-axis designs, further protect the from thermal damage. Through these observations, solar telescopes contribute to a deeper understanding of solar cycles, explosive flares, looping prominences, and coronal mass ejections (CMEs), all of which drive that can disrupt Earth's climate patterns, radio communications, and electrical grids. This research is vital for mitigating the societal impacts of solar events, such as geomagnetic storms that threaten technology-dependent infrastructure.

Historical Development

The earliest telescopic observations of the Sun were made in the early using simple refracting telescopes, with among the pioneers who systematically documented sunspots starting in 1610. These observations, conducted by projecting the Sun's image onto a surface to avoid direct viewing, revealed dark spots moving across the solar disk, providing evidence of the Sun's rotation with a period of about 27 days and challenging the Aristotelian view of perfect celestial bodies. In the , advancements enabled more detailed studies, including the invention of the spectroheliograph by in 1889, which allowed imaging the Sun in specific wavelengths to reveal chromospheric features. During this period, solar prominences—bright, gaseous structures extending from the Sun's surface—were first observed outside of total eclipses using , beginning with and in 1868, with Angelo Secchi contributing detailed records starting in 1871. The early 20th century marked the establishment of dedicated solar observatories, such as the Mount Wilson Solar Observatory founded by Hale in 1904, which featured the Snow Solar Telescope in 1905 and the 60-foot tower telescope completed in 1908. These facilities introduced coelostats—rotating mirrors that track the Sun and direct its light to a fixed horizontal —for stable, high-resolution imaging without moving the main telescope structure. By the mid-20th century, efforts to mitigate atmospheric turbulence led to innovative designs like the 50-foot tower telescope at the McMath-Hulbert Observatory, operational from 1936, which elevated optics above ground-level seeing effects. Post-World War II developments included precursors to , such as early wavefront correction techniques tested on solar instruments in the 1950s and 1960s to compensate for air distortions. The era also saw the rise of vacuum tower telescopes, exemplified by the McMath-Pierce Solar Telescope dedicated in 1962, which evacuated the light path to eliminate internal air currents and improve image stability. In the late , solar telescopes grew in aperture size and fostered international collaborations, with the 50-cm Swedish Vacuum Solar Telescope commencing operations in 1972 at the Observatorio del Teide, later upgraded to a 1-m instrument in the early for enhanced resolution of solar dynamics. These advancements emphasized multi-wavelength observations and global data sharing, laying groundwork for modern solar research networks.

Design Principles

Optical Configurations

Solar telescopes employ a variety of optical configurations to capture and process the intense while minimizing distortions and effects. Early designs predominantly utilized refracting telescopes with achromatic lenses, which consist of two or more elements—typically crown and —to correct for by bringing different wavelengths to a common focus. These refractors were suitable for small to medium apertures, such as the 25-cm objective at the , enabling monochromatic observations like H-alpha imaging with minimal color fringing. However, modern solar telescopes favor reflecting configurations, particularly off-axis designs, to avoid central obstructions that cause and to reduce heat buildup on the primary optic, as seen in the 4-m (DKIST), where the off-axis Gregorian layout provides an unobstructed aperture and space for a heat-stop at prime focus. Focal arrangements in solar telescopes emphasize long effective focal lengths to achieve high on the solar disk, with tower-based systems extending up to approximately 90 meters, as in the McMath-Pierce Solar Telescope, where a directs light down a vertical shaft to form a large image scale. This extended path enhances by magnifying solar features, producing images up to 333 mm in diameter for a 0.6-m at f/60. The Coudé focus configuration is commonly employed to relocate instrumentation to a stable, heat-isolated laboratory environment away from the main optical train, as implemented in DKIST's transfer optics that route the f/13 Gregorian beam to a coudé room for multiple instruments. Beam directing systems track the Sun's motion to deliver a stable light path into the telescope. Heliostats use a single rotating flat mirror on an to reflect along a fixed polar axis, though this introduces image rotation at 15° per hour, often compensated by derotators like Dove prisms. Coelostats, by contrast, employ a fixed primary mirror and a rotating secondary on an alt-azimuth setup to produce a non-rotating horizontal beam, ideal for fixed spectrographs, as in the German Vacuum Tower Telescope. Specialized filters and polarimetric optics enable targeted observations of . Coronagraphs occult the bright solar disk to reveal the faint inner corona, typically using an external occulter and internal stops to suppress stray light, as in the Metis instrument on , which employs an inverted external occulter and a back-rejecting spherical mirror to image from 1.7 to 3.1 solar radii with reduced thermal load. Tunable Fabry-Pérot etalons provide narrowband filtering for spectral lines like H-alpha (656.3 nm), with bandpasses of tens to hundreds of milliangstroms adjusted via cavity spacing or tilt according to the relation mλ=2μdcos⁡θm \lambda = 2 \mu d \cos \theta, allowing dynamic scanning of solar features. Vector magnetographs map solar by measuring Zeeman-induced polarization, using quarter-wave plates and analyzers in a , as in the SVM-I at , which employs a piezo-scanned etalon and polarizers to derive across the 630 nm Fe I line. The theoretical resolution limit for these systems is governed by diffraction, given by θ≈1.22λ/D\theta \approx 1.22 \lambda / D in radians, where λ\lambda is the and DD the ; converting to arcseconds yields θ≈252,000λ/D\theta \approx 252,000 \lambda / D. For visible at λ=500\lambda = 500 nm and a 4-m aperture like DKIST, this approaches 0.04 arcseconds, resolving features as small as 30 km on the Sun and underscoring the need for large apertures to overcome this fundamental limit.

Thermal and Seeing Management

Solar telescopes must manage intense thermal loads from concentrated sunlight, which can cause optical distortions through heating of components and induce internal seeing effects from currents. The primary heat load arises from , approximately 1 kW/m² at the Earth's surface, absorbed by the telescope's over its area, with the absorbed power calculated as Q=I⋅A⋅(1−R)Q = I \cdot A \cdot (1 - R), where II is , AA is the collecting area, and RR is the reflectivity of the surface. This heat must be rejected efficiently to maintain and image quality, as even small gradients can warp mirrors or create turbulent air flows within the instrument. Heat rejection strategies begin with a heat-stop positioned at the primary focus, which reflects over 95% of incoming solar radiation to prevent excessive absorption downstream, dissipating the remainder through radiative and convective cooling while keeping surface temperatures near ambient levels. For the primary mirror, systems circulate coolants such as water or synthetic fluids through embedded channels, maintaining temperature variations below 1°C to minimize and errors. Vacuum chambers or evacuated sections along the further reduce convective heating by eliminating air-mediated , a technique employed in early designs to suppress internal . These measures ensure that the telescope's remain thermally stable, with noncontact estimation methods verifying mirror temperatures in real time via models. Atmospheric seeing, caused by turbulence in the air layers above the , degrades resolution, but solar telescopes counteract this using (AO) systems that employ wavefront sensors to measure distortions and deformable mirrors to correct them in real time. Pioneered at facilities like the Dunn Solar Telescope, these systems achieve near-diffraction-limited imaging by compensating for the Sun's extended brightness as a natural guide source, unlike night-time astronomy's point stars. Multi-conjugate AO extends correction to multiple atmospheric layers using sequential deformable mirrors, widening the field of view and improving uniformity, as demonstrated at the New Solar Telescope. Site selection plays a critical role in minimizing seeing and thermal effects, favoring high-altitude locations with low content, such as in or the , where reduced atmospheric thickness and stable boundary layers limit turbulence. Off-axis optical designs further mitigate ground-induced seeing by directing light paths away from heated telescope structures and surrounding terrain, avoiding convective plumes from the ground. Enclosures incorporate vent systems to promote airflow, flushing heated air and equalizing internal temperatures with the ambient environment during observations. Laser guide stars, while common in night-time AO, are impractical for solar applications due to the Sun's brightness overwhelming artificial beacons. Modern advancements integrate these elements for enhanced performance, with real-time AO processing enabling high-order corrections up to thousands of actuators, as seen in recent observations of fine coronal structures. Thermal modeling informs cooling requirements by simulating heat loads and airflow, ensuring designs like those for the European Solar Telescope handle up to 13 kW while preserving optical stability.

Types of Solar Telescopes

Professional Instruments

Professional solar telescopes are large-scale facilities designed for advanced research, featuring apertures typically ranging from 1 to 4 meters to capture sufficient solar flux for high-resolution studies. These instruments are primarily funded by governmental and international bodies, such as the U.S. (NSF) for facilities like the (DKIST) and a multinational of European countries, supported by programs including Horizon 2020 for preparatory phases and subsequent initiatives like , for the planned 4-meter European Solar Telescope (EST). As of November 2025, the project has established a Board of Governmental Representatives to oversee construction, with first light expected around 2030. Such supports multi-wavelength observations spanning (starting at 380 nm), visible, and (up to 2300 nm) regimes, enabling comprehensive analysis from the to the corona. Key instrumentation includes spectro-polarimeters, which measure in spectral lines to derive Doppler velocities and magnetic field strengths in solar plasma with sub-arcsecond and spectral resolutions exceeding 100,000. arrays, such as HgCdTe or InSb sensors, are employed to probe cool features like sunspots, using lines like Fe I at 1565 nm to map magnetic fields up to 2500 G and reveal penumbral structures. spectrometers focus on the transition region, capturing emissions from ions to study chromospheric dynamics, though ground-based access is limited and often supplemented by space missions. These telescopes operate in continuous daytime modes, with automated data pipelines processing high-cadence observations (e.g., multiple frames per second) to generate real-time products for forecasting, including magnetograms and velocity maps. International collaborations, such as the Global Oscillation Network Group (), provide 24/7 global coverage via six identical sites, achieving over 90% for helioseismology and synoptic monitoring essential to alerts. Facilities like the National Solar Observatory's Dunn Solar Telescope exemplify this, using its 0.76 m aperture in a tower to deliver high-resolution imaging and of photospheric features. Integration with computational resources allows these instruments to support advanced simulations, correlating observational data with models of solar convection and . Since the early , emphasis has shifted to 4 m-class designs, enabling resolution of fine structures under 100 km on the solar surface—approximately three times finer than prior generations—for detailed studies of and turbulence. Many incorporate systems to mitigate atmospheric seeing, achieving near-diffraction-limited performance across broad fields of view.

Amateur Setups

Amateur astronomers can observe the Sun using compact, affordable equipment designed for safe and accessible solar viewing. Small refractor telescopes with apertures between 50mm and 150mm, equipped with full-aperture solar filters, are popular entry-level options for white-light observations of sunspots and the solar disk. These filters, such as Baader AstroSolar Safety Film with an optical of 5.0, block 99.999% of incoming to prevent damage to the instrument and ensure safe viewing. (H-alpha) telescopes, which isolate the 656.3 nm emitted by in the solar chromosphere, offer views of prominences, filaments, and spicules; examples include the Coronado Personal Solar Telescope (PST), a 40mm instrument with internal <1 bandpass filtering for portable H-alpha . Safety is paramount in amateur solar observing, as direct exposure to unfiltered can cause permanent eye damage. Observers must never point unfiltered at the Sun and should use full-aperture solar filters from reputable manufacturers that meet safety guidelines for astronomical use, such as those with an optical density of at least 5.0 in the to block harmful UV and IR , as recommended by the (AAS). These filters maintain color neutrality and durability against solar heat. Handheld or glasses meeting ISO 12312-2:2015 criteria can supplement use during events like partial s. Basic observation techniques focus on visual and simple imaging of solar features. Visually, amateurs spot sunspots as dark umbrae with lighter penumbrae, dark filaments against the disk, and the mottled texture of photospheric granules on clear days. For imaging, webcams or modified digital cameras attached to the capture short videos, which are then processed using stacking software like AutoStakkert! to align and combine frames, reducing noise and enhancing contrast for features like faculae or active regions. This method allows hobbyists to produce detailed images of the visible solar disk without advanced setups. Amateur solar setups are highly accessible, with costs ranging from $200 for basic refractors and filters to $2,000 for dedicated H-alpha systems like the Coronado PST or Lunt 50mm models. Community events, such as public viewings organized by astronomy clubs, provide hands-on opportunities, while mobile apps like SpaceWeatherLive deliver real-time forecasts of solar activity, including numbers and alerts, to optimize observing sessions. These tools enable participation from urban backyards or remote sites without specialized infrastructure. Limitations of amateur setups include reduced angular resolution compared to professional instruments, typically constrained by atmospheric seeing to about 1 arcsecond, versus 0.05 arcseconds achievable with adaptive optics in large observatories. Observations thus emphasize broad disk features like sunspot groups and limb prominences rather than fine chromospheric details.

Specialized Designs

Heliostat and Coelostat Systems

Heliostats are optical devices consisting of a single large flat mirror mounted on an equatorial drive that tracks the Sun's apparent motion across the sky, reflecting sunlight into a fixed telescope or instrument below. This design allows for compact solar telescope setups by directing the solar beam downward or horizontally without requiring an extended tube structure, thereby minimizing mechanical stress from long focal lengths. The mirror typically rotates at the solar rate, approximately equal to Earth's rotational speed of 15′′/s15''/\mathrm{s}, to maintain alignment with the Sun. Coelostats, in contrast, employ a two-mirror to produce a stationary image of the Sun, with a primary flat mirror mounted parallel to Earth's polar axis and rotating at half the solar rate—also derived from the 15′′/s15''/\mathrm{s} equatorial tracking rate—to compensate for , while a fixed or slowly adjusting secondary mirror directs the beam to the instrument. Invented by French physicist Gabriel Lippmann in 1895, this configuration eliminates image rotation inherent in single-mirror systems, facilitating stable attachment of heavy instrumentation like spectrographs or polarimeters directly to a fixed focal plane. Both systems offer key advantages in solar astronomy, including reduced mechanical complexity compared to fully rotating large telescopes and the ability to feed a single collected beam to multiple instruments simultaneously, such as in setups where stable pointing is essential. For instance, the McMath-Pierce Solar Telescope at employs a atop its tower to direct sunlight down a vacuum shaft for high-resolution observations. Coelostats are particularly valued for long-exposure studies, as seen in the German Vacuum Tower Telescope (VTT) on , where the system supports two-dimensional spectropolarimetry with polarization efficiencies exceeding 50% at 630 nm and spatial resolutions better than 0.5 arcsec when paired with . Historically, these devices have enabled precise solar imaging since the late , evolving to integrate with tower structures for elevated, seeing-minimized paths. Despite their benefits, heliostats and coelostats require stringent mirror alignment to prevent image wander, with tracking accuracies typically better than 0.1 arcsec over short intervals to avoid degrading resolution in fine-scale solar features. Heliostats suffer from field rotation at 15° per hour, necessitating derotators like Dove prisms for extended observations, while coelostats demand precise synchronization of the two mirrors to mitigate time-varying incidence angles that could introduce polarization artifacts in modern applications.

Tower Telescopes

Tower telescopes employ vertical architectural designs that elevate the high above the ground to mitigate atmospheric seeing effects. These structures typically consist of tall towers, typically 30 to 50 meters in height, such as the McMath-Pierce Solar Telescope's 30.5-meter tower combined with an extensive underground shaft for a total light path exceeding 150 meters. Sunlight is captured by a at the tower's apex and directed horizontally into an evacuated tube that extends downward, housing the primary at the base. This elevation positions the light path above the turbulent atmospheric near the surface, significantly reducing distortions from ground-heated air . The design facilitates exceptionally long effective focal lengths, often between 50 and 200 meters, which support magnifications up to several thousand times for high-resolution imaging. For instance, the 60-foot Solar Telescope, completed in 1908 at , achieves an 18-meter to enable detailed spectroheliograph observations. The evacuated enclosure of the light path prevents internal air currents and thermal gradients that could induce variations, thereby preserving image sharpness by eliminating convection-induced turbulence. Contemporary implementations incorporate advanced features like to compensate for residual atmospheric aberrations. The New Solar Telescope at Solar Observatory exemplifies this hybrid approach, with its 83-meter effective and integrated AO system for real-time wavefront correction. These towers deliver superior , on the order of 0.1 arcseconds or better, crucial for investigating solar granulation patterns and convective dynamics. Despite these advantages, the elevated frameworks face engineering hurdles, including heightened vulnerability to wind-induced vibrations and substantial construction expenses for reinforced supports and vacuum maintenance.

Notable Facilities

Historical Examples

The Snow Solar Telescope, relocated to Mount Wilson Observatory in 1904 by George Ellery Hale, was one of the earliest dedicated solar instruments. This horizontal telescope, using a coelostat to direct sunlight, enabled initial high-resolution studies of sunspots and solar spectra, marking the beginning of systematic solar observation at altitude to reduce atmospheric distortion. The 60-Foot Solar Tower at Mount Wilson, completed in 1908, introduced a vertical configuration with a heliostat atop a 60-foot (18-meter) tower. This design improved image stability by placing optics above turbulent boundary layers, facilitating spectroscopic observations that advanced understanding of solar magnetic fields. The 150-foot Tower Solar Telescope at , operational since 1912 and later upgraded in the 1960s with enhanced spectrograph capabilities, stood as a cornerstone for long-term solar monitoring. Its vertical design and system provided stable, high-resolution views, where early helioseismology experiments in the 1960s detected oscillations in the Sun's surface, linking them to internal dynamics. It also documented variations across the 11-year , contributing to models of solar activity prediction. The McMath-Pierce Solar Telescope, dedicated in 1962 at with a 1.6-meter entrance , represented a significant leap in solar instrumentation due to its unprecedented 87-meter achieved through a series of mirrors. This design minimized atmospheric distortion and allowed for high-dispersion spectroscopy, pioneering infrared observations of the solar spectrum that revealed new absorption lines and temperature profiles. Throughout the mid-20th century, it facilitated key studies on solar granulation and , influencing subsequent telescope designs. The Richard B. Dunn Solar Telescope at Sacramento Peak Observatory, featuring a 76 cm (0.76-meter) and a 65-meter evacuated tower commissioned in 1970, advanced vacuum tower technology to suppress thermal turbulence. Building on the observatory's origins in 1947 for solar flare monitoring during and after , it enabled precise imaging of correlated with radio bursts in systematic observations, improving understanding of solar activity's impact on Earth's and radio communications. By the early 2000s, many 20th-century solar towers, including the McMath-Pierce facility decommissioned in 2018, faced decommissioning due to advancements in and that rendered older vacuum and long-focal-length systems less efficient for modern research demands. This shift allowed resources to be redirected toward more versatile ground- and space-based observatories.

Modern and Future Telescopes

The (DKIST), located on in , , represents the pinnacle of contemporary ground-based facilities, achieving first light in 2019 with a 4-meter off-axis Gregorian primary mirror that collects more sunlight than any other solar telescope. This design minimizes scattered light and thermal distortion, enabling unprecedented views of solar features down to approximately 0.03 arcseconds in resolution when paired with advanced systems. DKIST's suite of instruments, including spectro-polarimeters and narrowband imagers, facilitates detailed studies of processes in the solar atmosphere, contributing to improved models of solar eruptions and impacts. In the , the GREGOR telescope, operational since 2012 at the in , features a 1.5-meter optimized for high-resolution imaging and spectro-polarimetry in visible and near-infrared wavelengths. Its open-air Gregorian configuration, supported by , allows for efficient air flushing to reduce seeing effects, while fiber-fed spectrographs like enable precise measurements of chromospheric dynamics, such as wave propagation and evolution. Funded through collaborations involving German and Spanish institutions, GREGOR has advanced understanding of solar convection and oscillations through its versatile post-focus instrumentation. The Swedish 1-m Solar Telescope (SST), situated at the on since 2003, exemplifies refined vacuum-lens technology for diffraction-limited performance, upgraded in 2010 with multi-conjugate to achieve resolutions approaching 0.1 arcseconds. This facility excels in high-cadence imaging of atmospheric waves and magnetic structures using instruments like CRISP and CHROMIS, which provide spectropolarimetric data across multiple wavelengths. SST's commitment to an policy, with public archives of processed observations, has fostered collaborative research on solar magnetism and dynamic phenomena. Looking ahead, the European Solar Telescope (EST), a 4-meter class instrument planned for the Roque de los Muchachos Observatory with first light targeted for 2027, will incorporate multi-conjugate adaptive optics to deliver sub-arcsecond resolution across the solar atmosphere. Its design supports up to eight simultaneous instruments, including polarimeters and spectrographs, focused on tracing magnetic connectivity from the photosphere to the corona. Construction preparations advanced in 2023 with the establishment of an international foundation, building on preparatory phases initiated in 2021 to ensure integration of cutting-edge diagnostics for solar plasma physics. Emerging trends in solar telescopy emphasize the fusion of with observational data to handle the vast volumes generated by these facilities, as seen in models applied to DKIST datasets for real-time atmospheric visualization and property . Global networks, such as the NSF-funded Global Oscillation Network Group () with its six synchronized stations, enable continuous 24-hour monitoring of solar oscillations and activity, complemented by proposed expansions like the NSO's next-generation worldwide array. Aperture sizes exceeding 4 meters, as in DKIST and EST, are driving capabilities toward sub-arcsecond views of the low corona, enhancing studies of faint emissions and through increased light-gathering power and advanced correction.

References

  1. https://www.buffalo.edu/ubnow/stories/2025/09/solar-telescope.html
  2. https://www.su.se/institute-for-solar-physics/the-telescope/design-1.638544
  3. https://sunspot.nmsu.edu/about/dunn-solar/index.html
  4. https://noirlab.edu/public/images/noao-02482/
  5. http://www.livingreviews.org/lrsp-2011-2
  6. https://nso.edu/telescopes/dkist/fact-sheets/dkist-overview/
  7. https://nso.edu/telescopes/inouye-solar-telescope/
  8. https://nso.edu/press-release/groundbreaking-achievement-nsf-inouye-solar-telescope-produces-first-magnetic-field-maps-of-the-suns-corona/
  9. https://www.mtwilson.edu/vt-snow-solar-telescope/
  10. https://www.mtwilson.edu/discovering-mount-wilson-chapter-16-hale-nicholson-law/
  11. https://noirlab.edu/public/news/noao9807/
  12. https://adsabs.harvard.edu/full/2003cigs.book.....P
  13. https://www.nsf.gov/news/nsfs-newest-solar-telescope-produces-first-images
  14. https://solarscience.msfc.nasa.gov/SunspotCycle.shtml
  15. https://nso.edu/telescopes/dkist/fact-sheets/dkist-space-weather/
  16. https://nso.edu/telescopes/dkist/fact-sheets/dkist-instruments/
  17. https://nso.edu/telescopes/dkist/fact-sheets/resisting-the-heat/
  18. https://www.swpc.noaa.gov/sites/default/files/images/u2/Chapter_4_mod2-FINAL.pdf
  19. https://galileo.library.rice.edu/sci/observations/sunspots.html
  20. https://www2.hao.ucar.edu/education/about-the-sun/what-are-some-historical-observations-sun
  21. https://adsabs.harvard.edu/full/1943PASP...55..184P
  22. https://ui.adsabs.harvard.edu/abs/2021JSWSC..11...51C/abstract
  23. https://www.mtwilson.edu/vt-60-foot-solar-telescope/
  24. https://adsabs.harvard.edu/full/1939POMic...7....1M
  25. https://noirlab.edu/public/programs/kitt-peak-national-observatory/mcmath-pierce-solar-telescope/
  26. https://www.aanda.org/articles/aa/full_html/2019/06/aa35735-19/aa35735-19.html
  27. https://www.tifr.res.in/~antia/nandita.pdf
  28. https://link.springer.com/article/10.1007/s11207-020-01736-7
  29. http://bzhang.lamost.org/upload/astron/cphistory.html
  30. https://link.springer.com/article/10.1007/s10686-020-09662-z
  31. https://www.ias.ac.in/public/Volumes/joaa/027/02-03/0285-0292.pdf
  32. https://arxiv.org/abs/1102.0111
  33. https://www.spiedigitallibrary.org/journals/Journal-of-Astronomical-Telescopes-Instruments-and-Systems/volume-7/issue-3/038003/Modeling-and-experiment-validation-of-thermal-control-for-the-heat/10.1117/1.JATIS.7.3.038003.full
  34. https://www.researchgate.net/publication/305686543_Active_thermal_control_for_the_18-m_primary_mirror_of_the_solar_telescope_CLST
  35. https://iopscience.iop.org/article/10.1088/1748-0221/19/08/P08031
  36. https://www.spiedigitallibrary.org/journals/Journal-of-Astronomical-Telescopes-Instruments-and-Systems/volume-3/issue-4/046001/Noncontact-temperature-estimation-method-on-the-actively-cooled-primary-mirror/10.1117/1.JATIS.3.4.046001.full
  37. https://nso.edu/telescopes/dkist/fact-sheets/dkist-adaptive-optics/
  38. https://pmc.ncbi.nlm.nih.gov/articles/PMC4841189/
  39. https://nso.edu/press-release/next-generation-of-adaptive-optics-widens-the-field-for-observations-of-the-sun/
  40. https://www.aanda.org/articles/aa/full_html/2017/01/aa29970-16/aa29970-16.html
  41. https://nso.edu/press-release/three-sites-selected-as-candidates-for-worlds-largest-solar-telescope/
  42. http://www.bbso.njit.edu/newtelescope/large.html
  43. https://bbso.njit.edu/nst_publ/NST_align.pdf
  44. https://nso.edu/telescopes/dkist/enclosure/
  45. https://est-east.eu/enclosure
  46. https://link.springer.com/article/10.12942/lrsp-2011-2
  47. https://www.nature.com/articles/s41550-025-02564-0
  48. https://www.aanda.org/articles/aa/full_html/2022/10/aa43867-22/aa43867-22.html
  49. https://www.est-east.eu/funding
  50. https://www.spiedigitallibrary.org/journals/optical-engineering/volume-58/issue-08/082417/Instrumentation-for-solar-spectropolarimetry--state-of-the-art-and/10.1117/1.OE.58.8.082417.pdf
  51. https://pmc.ncbi.nlm.nih.gov/articles/PMC4841185/
  52. https://iopscience.iop.org/article/10.1088/1538-3873/ac24d5
  53. https://nso.edu/telescopes/nisp/gong/
  54. https://link.springer.com/article/10.1007/s11207-025-02503-2
  55. https://eclipse.aas.org/eye-safety/optics-filters
  56. https://www.iso.org/standard/59289.html
  57. https://www.autostakkert.com/
  58. https://www.highpointscientific.com/solar-filters-telescopes
  59. https://www.spaceweatherlive.com/en/app.html
  60. https://www.telescope-optics.net/telescope_resolution.htm
  61. https://adsabs.harvard.edu/full/1984SoPh...93..211D
  62. https://www.nobelprize.org/prizes/physics/1908/lippmann/biographical/
  63. https://www.aanda.org/articles/aa/full_html/2010/12/aa13441-09/aa13441-09.html
  64. https://www.prl.res.in/~uso/mast.pdf
  65. http://www.scholarpedia.org/article/Solar_telescopes
  66. https://www.som.com/projects/mcmath-pierce-solar-telescope/
  67. https://adsabs.harvard.edu/full/1985SoPh..100....1D
  68. https://opg.optica.org/abstract.cfm?uri=ao-3-12-1353
  69. http://www.bbso.njit.edu/newtelescope/
  70. https://www.aanda.org/articles/aa/abs/2001/09/aah2397/aah2397.html
  71. https://noirlab.edu/public/images/noao-02573/
  72. https://nso.edu/telescopes/dkist/fact-sheets/follow-the-photons/
  73. https://www.nsf.gov/news/daniel-k-inouye-solar-telescope-starts-year-long
  74. https://www.iac.es/en/observatorios-de-canarias/telescopes-and-experiments/gregor-solar-telescope
  75. https://www2.mps.mpg.de/dokumente/publikationen/solanki/j360.pdf
  76. https://www.aanda.org/articles/aa/full_html/2016/12/aa30019-16/aa30019-16.html
  77. https://www.su.se/institute-for-solar-physics/the-telescope
  78. https://www.iac.es/en/observatorios-de-canarias/telescopes-and-experiments/swedish-solar-telescope
  79. https://dubshen.astro.su.se/sst_archive/
  80. https://www.est-east.eu/european-solar-telescope
  81. https://www.iac.es/en/outreach/news/european-solar-telescope-project-presents-design-its-construction-roque-de-los-muchachos-observatory
  82. https://datascience.hawaii.edu/ai-and-astronomy-uh-researchers-to-help-decode-suns-secrets/
  83. https://www.est-east.eu/est-project
Add your contribution
Related Hubs
Contribute something
User Avatar
No comments yet.