You read the title correctly: that's an aperture 8.4 meters wide! The camera itself is the Large Binocular Telescope atop Mount Graham in Arizona. Admittedly, the title is a bit tricky. To capture an optical image, a CCD device, mounted on a boom, is swung into the optical path. The front element of this device is a "minuscule" 810 mm! For those technically-gifted readers out there, here is a diagram of the device:
Here is what the CCD device looks like. I have one on order from B & H!
That's some camera! What do the primary mirrors look like? The two primary mirrors are mounted side-by-side. Here is one of them:
Here is a shot of both mirrors, taken just before dusk as a team of Italian astronomers was preparing the LBT for a night of work:
Periodically, these big mirrors need to be re-coated with a fine layer of super pure aluminium. To to this, the mirror is released from its mount, hoisted up by a large overhead crane, then lowered through a trap door next to the telescope down to the mirror coating facility below:
Tilting is accomplished with a very tiny electric motor since the telescope is so finely balanced. Rotating is another matter, because everything must rotate, including the concrete floor the telescope is mounted on.
Trust me: these photographs do not capture the grandeur of this facility. Everything is amazing. Everything is breathtaking. I often see photos of cars on the blogs of famous photographers. When I do, I smile. I smile because even though expensive sports cars are cool, and I myself enjoy photographing them, they are NOTHING compared the cutting-edge tools of science.
The LBT is closed to the public. Sandy and I are extremely fortunate to have the acquaintance of Joan Green and her astronomer husband Richard Green. It pays to have friends:
Other facilities such as Kitt Peak are open to the public. I urge all of you to visit an astronomy facility if you can. Observatories are more than just buildings housing telescopes. They have living quarters, kitchens, dining and entertainment areas, mirror coating machines, repair, maintenance and even medical facilities. Science is amazing!