Really Big Binoculars

By Phil Plait | November 6, 2005 10:23 pm

Take a look at this:

Cool, huh? It’s NGC 891, a relatively closeby edge-on spiral galaxy. OK, now keep that picture in mind for a sec while I digress.

A couple of years ago I bought a pair of binoculars at a star party. They’re pretty nice, and I can see amazing stuff from my back yard (the Crab Nebula is a pretty easy target on a clear, moonless night). The problem is, they’re so big that holding them is hard. The lenses are a full 7 centimeters across, and the binocs weigh about 1.5 kilos (3 pounds), so I can hardly keep them pointed. I bought a tripod to hold them up, which has helped a lot.

So I like them, and they’re big enough to be impressive. At least, I used to think so. Then I heard about the LBT… the Large Binocular Telescope. Unlike your typical telescope which has one mirror, the LBT uses two mirrors to observe its targets. And these aren’t small mirrors– they are 8.4 meters across each— the combined area is equivalent to a single mirror nearly 12 meters across. That’s huge! But it’s even better than that…

The mirrors are spaced several meters apart. By carefully combining the images produced by each mirror, details can be seen in an astronomical target that are far smaller than either mirror could do on its own. This technique is called interferometry, and it’s been used in radio astronomy for decades. It’s much harder at optical wavelengths, but we’re clever, we apes. LBT will be able to use it routinely to see objects as small as 0.005 arcseconds across. By comparison, Hubble’s resolution is about 0.1 arcseconds. That means LBT will be able to resolve an object just ten meters across if it were sitting on the Moon! Hubble’s resolution limit at that distance is about 200 meters.

Currently, just one mirror is operating at LBT. But when you have a half million square centimeters of mirror, you can still do a lot. You can go pretty deep (seeing faint objects) and see lots of detail. OK, now go and look at that image of the galaxy NGC 891 again. That image is really deep, showing faint stars and galaxies. It was taken by the LBT, of course, in what’s called the “first light” image (the first time the ‘scope actually observes a target in the sky).

The LBT, with one mirror tied behind its back, took that image in just 5 minutes of observing! That’s pretty impressive. Imagine what this thing can do when it’s let loose on a target for an hour, or for five hours!

And when the second mirror comes online, it’ll be more impressive. It’ll be able to easily resolve Jupiter’s moons, for example. It can look for planets orbiting other stars, and peer deep into the Universe to see what was happening a long time ago, near the time when the first stars formed.

When I was younger, this stuff was considered a pipe dream. Now it’s a reality. Sometimes I wonder what could possibly be next.


Comments (20)

  1. dark_matter

    Thats awfully cool.

    And the 100m OWL would be….well, I don’t think I have the words.

    Personally, I think we should stick a 100m on the MOON. That would make for some interesting observations…

  2. Blake Stacey

    Like, no way! Like, way!

    I was thinking that Olympus Mons would probably be about the best place in the Inner Solar System to do astronomy. You’ve got air so thin it’s practically vacuum, but you’re on a planet that provides more useful materials than the Moon. (And even if we terraformed the place, a mountaintop **that** high would still be better than Chile!) Let’s see, I heard Zubrin give some numbers in the 5e10 – 1e11 dollar range for a Mars expedition. On top of that, the cost of an OWL would be a rounding error.

    “First rule of government spending: why build one when you can have two at twice the price?” –S. R. Hadden

  3. I think the first rule of government make sense. Building only one is going to be twice the price anyway.

    Building a telescope off the planet is gonna 100 times (my estimate) the price, so research into ground based telescopes make more sense to me.

  4. Evolving Squid

    I have a pair of 80mm binos and a pair of 100mm binos. I use them quite a bit more than my telescope actually – easier to transport, easier to use, and you can see things that are hard to comprehend in a telescope due to the wider field of view. I also find binos are a great way to introduce other people to astronomy.

    I am really looking forward to seeing the types of images that will come from the completed/fully operational LBT.

  5. oooooo


    I want one…


  6. Chris

    Maybe that would be able to finally put to rest the “we never went to the Moon” lunatics (ha ha- pipe dream, I know).

  7. Kim

    I never understand why NGC 891 isn’t a Messier object. I was at the Grand Canyon doing a little observing once and 891 was a pretty obvious naked-eye object. (Along with just about everything else you might want to look at, actually.)

    I’d be interested in whether we could use the LBT to obtain parallax measurements on a Cepheid variable or other standard candle and tighten up some of the baseline distance measurements.

  8. Samara

    Holy Flying Spaghetti Monster

    Any update on when the second mirror will come up? If that was just one mirror…WOAH

    On the planet front, will it just be able to see large gas planets (like Jupiter) or will it be possible to see small rocky bodies (like Earth)

  9. Samara

    On a lighter note, we need to come up with more creative names than overwhelmingly large telescope

  10. F. Mozel

    Another project I’ve heard of is the Magdalena Ridge Observatory It will have a 400m optical interferometer made up of 10 1.4m telescopes. Really cool stuff.

  11. Evolving Squid

    On a lighter note, we need to come up with more creative names than overwhelmingly large telescope

    I’d bet a pound of macadmia nuts that, at some point – perhaps only in a meeting somewhere, the telescope was to be named “Binocular Large Telescope”, but the name was changed because of the abbreviation :)

  12. L. Fuller

    For the last couple of years, I have lived in an area where I can see the LBT from my front yard (I hold a degree in geology from the University of Arizona so feel especially proud of this ‘scope). I have tried, off and on, to explain the significance of this observatory to my co-workers… especially when we were so close to losing it to a forest fire last year… but with images like this one and those that will come out of the observatory in the near future… well, what can I say, the project speaks for itself!

  13. Personally, I rather like 10×50 binoculars. Much bigger gets too tiring to hold steady, and much more magnification is almost impossible to hold steady enough. We’ve got some 30×80 binoculars, but they require a mount. Anything that requires setup tends to discourage use.

  14. TJ

    How inspiring! I went to a star party back in the late 80s at the top of Mt. Pinos in California. Nice clear night, everyone with their red lens-covered flashlight and telescopes for days! I went to these star parties as often as I could, and was alwyas impressed with the equipment, tracking software, etc. that these ‘amateur’ astronomers had and used.

    The best view of Saturn I’d ever had though was through a pair of large binoculars. The binocs were not too common at these events, but this set was large, probably 10 or 11 cm outer lens. They were on a stand, of course! I stepped up, skeptical (go figure) at first since I know nothing about optics, then looked through thelarge binoculars. BANG! There was Saturn in all its ringed glory. Spectacular. Since then, I have never looked at binoculars the same way again…

  15. Evolving Squid

    I use these 25×100 and a set of 11×80 for which I don’t have the brand name handy (i.e. I’m too lazy to go look :) ) For both I have sturdy tripods that can raise them to almost 7 feet, which is good because there is a limitation of many optical mountings that is not well documented:

    They’re designed for people much shorter than 6’3″

    I don’t know how the stargazing is on nice, big, professional telescopes, but the amount of bending down I have to do to see through my telescope does limit my viewing time – hence the binos, which I can use standing up on the tall tripods, have a big advantage. If there’s anyone who has overcome this particular limitation for a celestron 8″ scope, please let me know :)

  16. P. Edward Murray


    I’m just a bit older than you are and I am just amazed at the technology that we all have today that was not available say when I was in Elementary School in the early 1970’s ..

    Pretty large machines that could record video and now are VCR’s that are almost extinct now!

    Astronomical CCD’s that you can pick up for $150 and webcams that cost less that can give you great photos of the Moon that didn’t exist back then!

    And these are “consumer” electronics that anyone can buy today…virtually unthinkable in the “60’s!

    I can only guess at what amateurs might be able to do in 100 years!

  17. P. Edward Murray

    Sorry , I meant High School!

  18. hale_bopp

    I have 20×80 binocs and a parallelogram mount. Very easy set up and very impressive views. I think it is the best visual view I have ever had of Andromeda was these things while observing at Apache Point.

    Oh, and I know the LBT director, so this was really cool seeing him on television promoting the first light image :)



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