Largest tip-tilt mirror in the world | ELT Updates

M5, the fifth mirror on the light path of ESO’s Extremely Large Telescope (ELT), has reached an important milestone: its blank, the shaped piece of material that is later polished to become the mirror, has just been finalised.
It might look small compared to the ELT’s enormous 39-metre primary mirror, but in reality, it is the largest tip-tilt mirror in the world. It will move 10 times per second without bending. Together with M4 - a flexible and very fast deformable mirror - they will both correct atmospheric turbulence and telescope vibrations, delivering sharp images.
Learn more about ESO's ELT at: elt.eso.org/
Credit:
ESO
Directed by: Angelos Tsaousis
Editing: Angelos Tsaousis
Web and technical support: Gurvan Bazin and Raquel Yumi Shida
Written by: Bárbara Ferreira
Footage and photos: ESO, L. Calçada, A. Tsaousis, M. Wallner.
Music: Jon Kennedy - A Tale of Pizzicato.
Acknowledgement: Mersen-Boostec.
This video can be downloaded on: www.eso.org/public/videos/ann...

[@bsmith9890]

I can't fathom how much care goes into an instrument as pricise as the ELT

[@ESOobservatory]

It's really challenging! Every component is significantly larger than in any previous telescope, but they still need to move and perform with exquisite accuracy.

[@AnakinSkywalker-mm3gi]

Is there a reason all the biggest telescopes on Earth are alt-az mounted? Are equatorial mounts not feasible for telescopes above a certain size?

[@ESOobservatory]

In equatorial mounts the gravity loads are more complex, since none of the axes is vertical. This makes them impractical for large and heavy telescopes whose mirrors are more than a few metres wide.

[@smeeself]

​@@ESOobservatoryThanks. 👍

[@DausHMS]

EQ mounts, because of their complexity, is also much more expensive. Its much simpler tracking never really justify its cost in large telescopes. Also alt-az mounts allow the telescope dome to be much more compact, further reducing the cost.