La Palma

CTA's site in the northern hemisphere

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Northern Hemisphere Array

Rendering Credit: Gabriel Pérez Diaz, IAC, SMM


CTA’s northern hemisphere site is located on the existing site of the Instituto de Astrofisica de Canarias’ (IAC’s) Observatorio del Roque de los Muchachos on the island of La Palma, the fifth largest island in the Canary Islands. At 2,200 metres altitude and nestled on a plateau below the rim of an extinct volcanic crater, the site currently hosts an operating gamma-ray observatory, the Major Atmospheric Gamma Ray Imaging Cherenkov (MAGIC) telescopes, as well as a wide variety of optical telescopes of various sizes.

Array Coordinates:

Longitude: 17º 53′ 31.218″ West
Latitude: 28º 45′ 43.7904″ North

Proposed Array Layout

While the southern hemisphere array will span the entire energy range of CTA, covering gamma-ray energies from 20 GeV to more than 300 TeV, the northern hemisphere array will be more limited in size and will focus on the low- and mid-energy ranges from 20 GeV to 20 TeV. For this reason, the northern hemisphere site will not host any Small-Size Telescopes, which are tuned to capture the highest-energy gamma rays. The plan is for the site to host four Large-Size Telescopes to capture the low-energy sensitivity of CTA and 15 Medium-Size Telescopes to cover CTA’s core energy range.

Large-Size Telescope Prototype Live Webcam


A Large-Size Telescope prototype is under construction on the La Palma site. Watch the construction live:

Announcements and Construction Updates

The foundation for a prototype of CTA’s largest telescope, the Large-Size Telescope, was completed on 11 January 2017. The main elements of the foundation, the telescope and the camera access tower foundations, were constructed with 620 cubic metres of concrete or about 1,500 tonnes! This massive amount of concrete will help keep the telescope and its mirror (400 square metres) stable with winds up to 200 km per hour. Additionally, a large area of the land next to the foundation has been flattened so it can be used to assemble the telescope structure.


The next step is to install the circular 23 m diameter rail used to spin the telescope, followed by the installation of six wheel bogies. The telescope structure is planned for installation between April and October. The camera access tower should be built in September and, in the final step, the camera is scheduled to be installed in November 2017.

The hosting agreement with the Instituto de Astrofisica de Canarias (IAC) was signed in September 2016 (read the press release). The agreement allows the construction of the CTA northern array to proceed at the Roque de los Muchachos site and ensures access to the infrastructure and common services needed for the operation of the Observatory.

On Friday, 9 October 2015, the first stone-laying ceremony for the Large Size Telescope (LST) prototype took place at the Roque de los Muchachos Observatory (ORM) on the island of La Palma (read the press release).