Saturday, July 14, 2007

First Light for the Gran Telescopio Canarias

Last night, the Gran Telescopio Canarias (GTC) at the Observatorio del Roque de los Muchachos of the European Northern Observatory (ENO) in La Palma, Canary Islands, Spain, saw its "First Light". The first star observed was Tycho 1205081, close to Polaris - a bit more photogenic is this shot of the pair of interacting galaxies UGC 10923 with extended star formation regions, taken with an exposure time of 50 seconds:

Interacting galaxies UGC 10923 seen with the eyes of the World's largest telescope (Credits: Gran Telescopio Canarias, Instituto de Astrofisica de Canarias)

The primary mirror of the new telescope consists is made up of 36 separate, hexagonal segments, fabricated at the Glaswerke Schott in Mainz, just around the corner from Frankfurt. Taken together, the segments have a light-collecting surface of 75.7 m2, which corresponds the a circular mirror with a diameter of 10.4 metres. At this size, it is the currently largest telescope for optical and near-infrared light!

The Gran Telescopio Canarias in La Palma, Canary Isles, in September 2006 (Credits: GTC project webcam)

This was in the news these days here (see e.g.,, or Le Monde), but the European Northern Observatory somehow has managed to issue a press release only in Spanish, so I am a bit at loss to find more details. Actually, the report in the FAZ is very good, and recalls the developments that lead to the construction of these huge telescopes:

I remember from the popular astronomy book I read as a kid that at that time the 5-metre mirror of the Mount Palomar telescope was thought to be the endpoint of the growth of telescope mirror size: Larger solid mirrors are to heavy and deform when the telescope is moved, and moreover, the image gets blurred anyway by the distortions caused to the light as it passes through the atmosphere. As a case in point, a 6-metre telescope in the Soviet Union was mentioned, which produced pictures of not as high a quality as expected from its size. I was quite disappointed when I read that.

Fortunately, both obstacles could be overcome with new technologies first realised in the 1990s: Active Optics, which means that the mirror is always kept in perfect shape by an array of motors and can therefore be lightweight, and large, and Adaptive Optics, which manages to compensate for the fluctuations of the density of air and allows for a seeing nearly as good as in space.

Among the big optical telescopes using these techniques - the Keck, Subaru and Gemini-North telescopes in Hawaii, the four mirrors of the Very Large Telescope and the Gemini-South telescope in Chile, the Large Binocular Telescope in Arizona, the Hobby-Eberly-telescope in Texas, and the South African Large Telescope in the South African Karoo - the Gran Telescopio Canarias is currently the largest one.

The good news is that all these telescopes will continue to take great shots of the Universe for the professionals and for armchair astronomers like me, even when the Hubble Space Telescope will once have stopped working.



  1. Hi Stephan,

    I found this photo of the unfinished primary mirror,showing the mechanicals inolved with the active/adaptive optics.


  2. Hi Mike,

    thank you for the link!

    Here are some more photos which show the mechanics of the telescope, albeit without further explanations. The general text about the the GTC is the same as in the link above.

    Best, stefan

  3. And here you can find more information on it too, including what Queen has to say about it. :-)

  4. Hi Urbano,

    great :-). Does Amara know that Brian May worked on dust in the Solar System? Problably yes...

    Best, stefan

  5. Dear Stefan,

    Absolutely! :-) I have been following the Brian May story; i.e. his PhD work on zodiacal dust. It's a fantastic story and I'm really tickled about what he did.

    He's not easy to reach, and honestly, I'm not sure yet I've been successful, but at least his publisher forwarded an important package from me and the interplanetary dust community, about one month ago, a gift to support him in his research, which is a book of the Proceedings of our 2005 Dust in Planetary Systems Meeting. There are at least 100 people in our community who are interested to read his thesis, when it is in its final form.

    P.S. I know that Brian May is difficult to reach because the head of the Solar Systems division of the European Space Agency (ESA) tried in 2004 to invite Brian to the launch of the Rosetta mission. This high-level ESA fellow was unsuccessful. I think that is a sad story, from both the perspective of Brian May (given his obvious enthusiam about astronomy), and from the perspective of ESA and the Rosetta scientists. I hope my smaller scaled attempt via his publisher will be more successful.

  6. Hi Stefan,

    great news! I am considering a week at the very same site... For visual observing! With a few amateurs we are searching for dark sites, and the roque de los muchachos seems a nice idea (I also have friends in Magic, which by the way has a mirror of 17m diameter... but works with Cherenkov light).

    As for the 50 seconds exposure, I am unimpressed! The pair is a 14.3 magnitude object, so with a 10m instrument I was hoping for more detail and more brightness.


  7. Have you seen this? It looks like it was a very nice event!

  8. Hi Stefan

    You can find information in english at the public consortium that built the telescope and at the astrophysics institute at the canary islands whose facilities host the new telescope.

    You might want to know that all the data collected by the different instruments to be used with the telescope (some of them already built some of them yet to be developed) will be considered 'public' and stored and archived in a external facility (I believe in Spain's mainland). The researchers will get a kind of some 'exclusivity' rights on the rough data during some period of time but after the period expires the rough data collected will be publicly available.

    I don't know if this is a common practice everywhere.



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