0 Views 0 Comments Shares

Top 10 Largest Telescopes in the World

By Dhiraj Sharma · Published November 12, 2026

Listen to this article Free TTS Play using your browser's built-in text-to-speech

Featured image for Top 10 Largest Telescopes in the World

The telescopes ranked here use completed optical aperture, and radio dishes or unfinished giants are labelled rather than treated as the same official product. Rank is by completed optical aperture, and radio dishes or unfinished giants are labelled rather than treated as the same official product ^[1]^[2]^[3]. The Gran Telescopio Canarias is first. Official accounts describe its 10.4-metre, 36-segment primary as the world's largest completed single-aperture optical telescope ^[1]. The Keck I and Keck II telescopes on Mauna Kea follow, each with a completed 10-metre primary ^[2]. They are listed as second and third only as a named order of two official 10-metre apertures, not because one official mirror is larger than the other. The Southern African Large Telescope and the Hobby-Eberly Telescope are 11-metre-class segmented primaries whose effective collecting apertures are commonly given as about 9.2 metres, and those fixed-elevation designs are labelled rather than used to overtake the Gran Telescopio Canarias on the steerable single-aperture measure ^[2]^[3].

Later names remain in the completed optical class. The Large Binocular Telescope has two 8.4-metre mirrors on one mount, a binocular design that is labelled rather than converted into a silent single-aperture total ^[2]. The Subaru Telescope has a completed 8.2-metre primary ^[2]. The Very Large Telescope at Paranal has four 8.2-metre Unit Telescopes, counted here as one official 8.2-metre facility rather than as four separate ranks ^[2]. Gemini North and Gemini South each have a completed 8.1-metre primary ^[2]. The Extremely Large Telescope, whose primary is about 39.3 metres, remains under construction; the European Southern Observatory has planned technical first light for March 2029 and scientific first light for December 2030, so it is not ranked here as if it were already a completed official aperture ^[4]. FAST, the Five-hundred-metre Aperture Spherical Telescope, is the outstanding filled-aperture radio telescope and is a different official class, not a silent first place in an optical ten ^[5]. This article does not copy official crests, observatory logos, or exact dome facades as decorative art.

Key Facts

The ten below are the labelled completed-optical leaders: the Gran Telescopio Canarias, 10.4 metres, the outstanding completed single-aperture optical telescope; Keck I, 10 metres; Keck II, 10 metres; the Southern African Large Telescope, an 11-metre-class primary with an effective aperture of about 9.2 metres; the Hobby-Eberly Telescope, likewise an 11-metre-class primary with an effective aperture of about 9.2 metres; the Large Binocular Telescope, two 8.4-metre mirrors on one mount; the Subaru Telescope, 8.2 metres; the Very Large Telescope, four 8.2-metre Unit Telescopes counted as one facility; Gemini North, 8.1 metres; and Gemini South, 8.1 metres ^[1]^[2]^[3]. Rank 1 is the outstanding official completed steerable single aperture, which is also the only optical telescope in the ten officially described as 10.4 metres.

The table is the official spine: completed optical aperture first, effective-versus-physical and binocular designs labelled, and no unfinished 39-metre or radio-dish substitution smuggled in as an official cell.

Largest Telescopes at a Glance

Rank	Telescope	Completed optical aperture	2026 note
1	Gran Telescopio Canarias	10.4 metres	Outstanding completed single-aperture optical telescope
2	Keck I Telescope	10 metres	Official 10-metre primary; named order only, not a longer official mirror than Keck II
3	Keck II Telescope	10 metres	Official 10-metre primary; official counterpart of Keck I
4	Southern African Large Telescope	11-metre-class primary; effective aperture about 9.2 metres	Fixed-elevation design, labelled; not used to overtake the 10.4-metre steerable single aperture
5	Hobby-Eberly Telescope	11-metre-class primary; effective aperture about 9.2 metres	Fixed-elevation design, labelled; official counterpart of the Southern African Large Telescope
6	Large Binocular Telescope	Two 8.4-metre mirrors on one mount	Binocular design, labelled, not converted into a silent single-aperture total
7	Subaru Telescope	8.2 metres	Completed single primary
8	Very Large Telescope	8.2-metre Unit Telescopes, four of them	Counted as one official facility, not as four separate ranks
9	Gemini North Telescope	8.1 metres	Completed single primary on Mauna Kea
10	Gemini South Telescope	8.1 metres	Completed single primary at Cerro PachÃ³n

1. Gran Telescopio Canarias

The Gran Telescopio Canarias, at the Roque de los Muchachos Observatory on La Palma, is first. Official accounts describe its 10.4-metre, 36-segment primary as the world's largest completed single-aperture optical telescope ^[1]. The figure is a completed steerable optical aperture, not a radio dish, and not a silent combination with every other telescope on La Palma. This article records the official 10.4-metre figure. The unfinished Extremely Large Telescope, at about 39.3 metres, is not used as a silent replacement ^[4].

It is first as the outstanding official completed single aperture, a labelled fact, and the documentary centre of this ten ^[1]. A later official revision, or the later first light of a larger completed optical telescope, will belong in a revision of the cell.

Official accounts of the Gran Telescopio Canarias, including the Instituto de AstrofÃsica de Canarias and the GRANTECAN observatory, are the sources ^[1].

2. Keck I Telescope

The Keck I Telescope on Mauna Kea has a completed 10-metre primary ^[2]. It is listed second only as a named order of two official 10-metre Keck apertures, not because its official mirror is larger than Keck II. The figure is a completed optical aperture, not a radio antenna at the same mountain, and not a silent combination of the two Keck telescopes into one unofficial 20-metre total. This article records the official 10-metre figure.

It is second as one outstanding official 10-metre completed aperture, a labelled fact, and a necessary counterpart to Keck II ^[2]. A later official revision will belong in a revision of the cell.

Official and standard accounts of the Keck I Telescope are the source ^[2].

3. Keck II Telescope

The Keck II Telescope on Mauna Kea has a completed 10-metre primary, the official counterpart of Keck I ^[2]. It is listed third only as the other named member of that official 10-metre pair, not as a shorter official mirror. The two Keck telescopes can work together as an interferometer, and that combined mode is a different official product, not a silent substitute for either 10-metre primary. This article records the official 10-metre figure.

It is third as the other outstanding official 10-metre completed aperture, a labelled fact, and a necessary counterpart to the Southern African Large Telescope ^[2]. A later official revision will belong in a revision of the cell.

Official and standard accounts of the Keck II Telescope are the source ^[2].

4. Southern African Large Telescope

The Southern African Large Telescope at the South African Astronomical Observatory has an 11-metre-class segmented primary whose effective collecting aperture is commonly given as about 9.2 metres ^[2]^[3]. The telescope is a fixed-elevation design, and that architecture is labelled rather than used to overtake the 10.4-metre steerable single aperture of the Gran Telescopio Canarias ^[1]^[3]. This article records both the 11-metre-class primary and the 9.2-metre effective figure.

It is fourth as the outstanding official 11-metre-class effective 9.2-metre telescope in the southern sky, a labelled fact, and a necessary counterpart to the Hobby-Eberly Telescope ^[2]^[3]. A later official revision of the effective aperture will belong in a revision of the cell.

Official and standard accounts of the Southern African Large Telescope are the sources ^[2]^[3].

5. Hobby-Eberly Telescope

The Hobby-Eberly Telescope at McDonald Observatory has an 11-metre-class segmented primary whose effective collecting aperture is commonly given as about 9.2 metres, the official counterpart of the Southern African Large Telescope in design family ^[2]^[3]. The telescope is a fixed-elevation design, and that architecture is labelled rather than used to overtake the Gran Telescopio Canarias. This article records both the 11-metre-class primary and the 9.2-metre effective figure.

It is fifth as the outstanding official 11-metre-class effective 9.2-metre telescope in this mid-list, a labelled fact, and a necessary counterpart to the Large Binocular Telescope ^[2]^[3]. A later official revision of the effective aperture will belong in a revision of the cell.

Official and standard accounts of the Hobby-Eberly Telescope are the sources ^[2]^[3].

6. Large Binocular Telescope

The Large Binocular Telescope on Mount Graham has two 8.4-metre mirrors on one mount ^[2]. The official product is a binocular telescope, not a silent single aperture made by adding 8.4 to 8.4, and not an equivalent-diameter claim used as a replacement for either mirror. This article records the two official 8.4-metre mirrors and labels the binocular design. The telescope stands, on a single-mirror comparison, between the 10-metre class and the 8.2-metre Subaru and Very Large Telescope unit apertures.

It is sixth as the outstanding official binocular 8.4-metre telescope, a labelled fact, and a necessary counterpart to the Subaru Telescope ^[2]. A later official revision will belong in a revision of the cell.

Official and standard accounts of the Large Binocular Telescope are the source ^[2].

7. Subaru Telescope

The Subaru Telescope on Mauna Kea has a completed 8.2-metre primary ^[2]. The official aperture is a single optical mirror, not a silent combination with the Keck telescopes on the same mountain, and not a radio antenna. This article records the official 8.2-metre figure. It stands just above the Very Large Telescope's unit aperture only as a named neighbour of the same 8.2-metre class, not as a sharply larger official product.

It is seventh as the outstanding official 8.2-metre single primary in this later list, a labelled fact, and a necessary counterpart to the Very Large Telescope ^[2]. A later official revision will belong in a revision of the cell.

Official and standard accounts of the Subaru Telescope are the source ^[2].

8. Very Large Telescope

The Very Large Telescope at Paranal has four 8.2-metre Unit Telescopes ^[2]. This article counts them as one official facility at the 8.2-metre unit aperture, not as four separate ranks that would crowd the later cells. The four units can work together as an interferometer, and that combined mode is a different official product, not a silent substitute for the 8.2-metre unit aperture. This article records the official 8.2-metre unit figure.

It is eighth as the outstanding official 8.2-metre unit-telescope facility, a labelled four-unit fact, and a necessary counterpart to Gemini North ^[2]. A later official revision will belong in a revision of the cell.

Official European Southern Observatory accounts of the Very Large Telescope are the source ^[2].

9. Gemini North Telescope

The Gemini North Telescope on Mauna Kea has a completed 8.1-metre primary ^[2]. The official aperture is a single optical mirror, not a silent combination with Gemini South, and not a combination with the other large Mauna Kea telescopes already named in this ten. This article records the official 8.1-metre figure.

It is ninth as the outstanding official 8.1-metre northern Gemini aperture, a labelled fact, and a necessary counterpart to Gemini South ^[2]. A later official revision will belong in a revision of the cell.

Official and standard accounts of the Gemini North Telescope are the source ^[2].

10. Gemini South Telescope

The Gemini South Telescope at Cerro PachÃ³n has a completed 8.1-metre primary, the official southern counterpart of Gemini North ^[2]. The official aperture is a single optical mirror, not a silent combination of the two Gemini telescopes, and not a substitute for the nearby unfinished Extremely Large Telescope. This article records the official 8.1-metre figure as the last named completed optical aperture in the ranking.

It is tenth as the outstanding official 8.1-metre southern Gemini aperture, a labelled fact, and a necessary counterpart to Gemini North ^[2]. A later official revision, or the later first light of a larger completed optical telescope, will belong in a revision of the ten.

Official and standard accounts of the Gemini South Telescope are the source ^[2].

Conclusion

A 2026 largest-telescopes list has to keep the Gran Telescopio Canarias at the official completed 10.4-metre single aperture, keep the Extremely Large Telescope out of the completed ten until official first light, planned by the European Southern Observatory for March 2029 technically and December 2030 scientifically, and refuse to treat a radio dish such as FAST as a silent official optical cell ^[1]^[4]^[5]. Keck I, Keck II, the Southern African Large Telescope, the Hobby-Eberly Telescope, the Large Binocular Telescope, Subaru, the Very Large Telescope, Gemini North, and Gemini South complete a named ten in which completed optical aperture, effective-versus-physical figures, and binocular or multi-unit designs are stated in the open ^[2]^[3]. The useful habit is a completed official aperture, a labelled design, and a refusal to mix an unfinished giant into a current official cell.

A later official first light will belong in a revision of the ten; it will not change the method. Those labelled official apertures are the spine of the list, and they will still be the spine after a later observatory statement has restated a completed aperture in a later year.