Tuesday, June 19, 2012

Two Telescopes

I own two telescopes right now, both refractors. One is 2.4 inches in diameter and the other is 4 inches in diameter.

I’ve talked a lot about telescopes, and I usually talk about telescopes larger than the two I own. (It’s almost a rule among amateur astronomers—you always talk about telescopes larger than what you own, whatever you own.)


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But I’ve also talked about what I consider the best approach these days to general amateur astronomy. I like the idea of a really well-made small scope on a computer-driven mount, along with a good pair of wide-angle binoculars. The combination is good for most kinds of amateur astronomy, except dim deep-sky objects, because those simply must have large aperture telescopes to be seen.

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Recently I saw a story about something all-together different. European scientists are planning to build the largest telescope in the world. It will be a reflector with a main mirror approximately 129 feet across. Here’s an artist’s rendering and an excerpt from the story, along with a couple of links:

Long, long ago, when backyard stargazers dreamed of owning a 6-inch reflector, I vividly remember making pilgrimages to Palomar Mountain in California to see the world's largest telescope. In the visitor's center was a massive concrete slab, bigger around than our family room, to represent the 200-inch (5-m) primary mirror of the famous Hale Telescope.

So my mind veritably boggles at the notion of a telescope so huge that its secondary mirror is nearly as big. Yet astronomers are now a step closer to that reality, because this week the European Southern Observatory's governing council approved construction of the European Extremely Large Telescope, or E-ELT. It's the no-nonsense moniker for an instrument destined to become the world's largest optical instrument, with a primary mirror 129 feet (39.3 m) across. That's 60% more aperture than the Giant Magellan Telescope now under construction and a third bigger than the proposed (but iffy) Thirty Meter Telescope.

As announced by ESO on June 11th, six of ESO's 14 member states have approved the project outright and four others have given provisional approval. The remaining four are expected to join the majority soon.

... And what might one do with a telescope this big? ESO astronomers hope exploit its visible-light and infrared prowess to find and scrutinize Earth-like planets in the "habitable zones" of other stars, measure characteristics of the first stars and galaxies to form after the Big Bang, and to probe the nature of dark matter and dark energy.

I don’t like so-called “big science” initiatives like this. I’m not an astrophysicist, but I don’t really believe the return on investment is reasonable at all. I’ve posted briefly about this before:

An Albireo Question

For example, astrophysicists don’t have any reasonable actual data on how many comets and asteroids impact Jupiter’s atmosphere every year. That data would provide pivotal information on the current constituents of our solar system, deepen our understanding of dangers of a possible Earth impact event and help us understand the history of the formation of our solar system. I strongly suspect a small spacecraft designed to orbit Jupiter and gather impact data would cost significantly less than the E-ELT.

But a small spacecraft is not as impressive politically as a giant building and new technology mirror mounts and all the “firsts” associated with the E-ELT. A small spacecraft orbiting Jupiter would be better science by almost every metric imaginable. But less politically impressive.

Big science is something I dislike very much, and I wanted to do this post so that I can refer back to it if I ever talk about big science again.

Here is one more picture of a telescope:

This is another reflector, and it is sort of the conceptual opposite of the E-ELT. The Astroscan is a 4 inch telescope with no mount at all. It is designed to provide a very wide field of view, similar to binoculars, and like binoculars you just hold it in your hands.

I’ve never owned an Astroscan, and I’ve never even looked through one. But I’ve heard people say good things about them, and I’ve never heard anyone say bad things about them. (It’s worth mentioning as an amateur astronomy aside that some astronomers have such affection for the Astroscan that they sometimes build larger or more advanced telescopes using the same basic design, just for fun. And sometimes they build larger flat-out copies of the Astroscan: A Great Big Astroscan by Jerry Oltion)

It’s not really a complicated gadget telescope, since there are no electronics involved, no computers. But if someone wanted to get a general purpose telescope, a simple gadget, without going the complicated gadget route, I’d recommend the Astroscan.

And I’ve mentioned the Astroscan once before.

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In my constant dream of moving onto a boat, a hand-held telescope like the Astroscan would be perfect. It gathers more light than binoculars, but doesn’t require a firm ground for a tripod. I hope to get one someday.

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