# Telescope **URL:** \ **Category:** Factual Questions\ **Created:** [October 3, 2001, 5:40am UTC](https://boards.straightdope.com/t/telescope/85137 "2001-10-03T05:40:06Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![RW55](https://avatars.discourse-cdn.com/v4/letter/r/ac8455/32.png) [@RW55](https://boards.straightdope.com/u/RW55)\ **Post date:** [October 3, 2001, 5:40am UTC](https://boards.straightdope.com/t/telescope/85137/1 "2001-10-03T05:40:06Z")
Not to long ago i saw a story on a new telescope being built that had two lenses. They thought that it might be able to see some of these Jupitor sized planets they have found. Did it not work like they wanted or is it not yet complete? ---
**Author:** ![douglips](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@douglips](https://boards.straightdope.com/u/douglips)\ **Post date:** [October 3, 2001, 9:20am UTC](https://boards.straightdope.com/t/telescope/85137/2 "2001-10-03T09:20:02Z")
I believe you may be talking about the [Keck Interferometer.](http://huey.jpl.nasa.gov/keck/) The telescope doesn’t have two lenses, it’s two telescopes (and eventually more than that) that combine their light to increase the resolution of their images in a process called “interferometry”, where the interference of two light beams is measured. This lets you get an image as if from a single telescope that is much larger than any of the component telescopes. It’s just getting started. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 4, 2001, 1:14am UTC](https://boards.straightdope.com/t/telescope/85137/3 "2001-10-04T01:14:55Z")
To actually image extrasolar planets, you have to go a few steps past the Keck. You take the same basic idea, but you launch the whole works into space. It looks very promising, but it’s not scheduled to go up yet for at least several years. ---
**Author:** ![Chas.E](https://avatars.discourse-cdn.com/v4/letter/c/e99b99/32.png) [@Chas.E](https://boards.straightdope.com/u/Chas.E)\ **Post date:** [October 4, 2001, 1:48am UTC](https://boards.straightdope.com/t/telescope/85137/4 "2001-10-04T01:48:42Z")
Hard to tell what he’s talking about. Refractors have multiple lenses, but all in one barrel, while many reflectors have no lenses, just mirrors. Most smaller scopes have a “guide scope” which is a smaller scope with a wider field of view, used for spotting the target of the larger scope. Or maybe he’s talking about the Keck Multiple Mirror telescope, but it has 6 mirrors. ---
**Author:** ![Earthling](https://avatars.discourse-cdn.com/v4/letter/e/90db22/32.png) [@Earthling](https://boards.straightdope.com/u/Earthling)\ **Post date:** [October 4, 2001, 3:47am UTC](https://boards.straightdope.com/t/telescope/85137/5 "2001-10-04T03:47:48Z")
Maybe the OP is talking about the [CHARA](http://www.skypub.com/news/news.shtml#chara) array on Mt. Wilson, which will consist of 6 1-meter telescopes when complete, but scientists just recently combined data from two (scroll down to Sept. 26). From the article: > [@](#): > > While the CHARA array can’t take “pictures” of extrasolar planets, it will be able to detect the wobbles that such planets induce on stars within binary systems. ---
**Author:** ![evilhanz](https://avatars.discourse-cdn.com/v4/letter/e/ba8739/32.png) [@evilhanz](https://boards.straightdope.com/u/evilhanz)\ **Post date:** [October 4, 2001, 4:02am UTC](https://boards.straightdope.com/t/telescope/85137/6 "2001-10-04T04:02:34Z")
I’m quite sure that the OP references NASA’s [Space Interferometry Mission (SIM)](http://sim.jpl.nasa.gov/) and the [Terrestrial Planet Finder (TPF)](http://tpf.jpl.nasa.gov/) program. SIM will be operational by 2009, TPF sometime after 2010. SIM is a survey and proof of concept project that will pave the way for imaging of extrasolar planets in the TPF program. NASA on SIM: > [@](#): > > The Space Interferometry Mission (SIM), scheduled for launch in 2009, will determine the positions and distances of stars several hundred times more accurately than any previous program. This accuracy will allow SIM to determine the distances to stars throughout the Galaxy and to probe nearby stars for Earth-sized planets. SIM will also pioneer a technique to block out (null) the light of bright stars to take images of the interesting areas close to the star. SIM will open a window to a new world of discoveries. The instrument specs can be viewed [here](http://sim.jpl.nasa.gov/flightsystem/index.html). The first segments will be in space in 2006. There are still several crucial hurdles in the project’s development that must be resolved before the TPF program can move beyond the drawing board. NASA descibes problems that must be resolved: > [@](#): > > (1) nanometer level control and stabilization of optical element positions on a lightweight flexible structure; > (2) sub-nanometer level sensing of optical element relative positions over meters of separation distance; > (3) overall instrument complexity and the implications for interferometer integration and test and autonomous on-orbit operation. NASA on TPF: > [@](#): > > By combining the high sensitivity of space telescopes with the sharply detailed pictures from an interferometer, TPF will be able to reduce the glare of parent stars by a factor of more than one hundred-thousand to see planetary systems as far away as 50 light years. In addition to measuring the size, temperature, and placing of planets as small as the Earth in the habitable zones of distant solar systems, TPF’s spectroscopy will allow atmospheric chemists and biologists to use the relative amounts of gasses like carbon dioxide, water vapor, ozone and methane to find whether a planet someday could or even now does support life. Here’s a simple [illustration](http://www.physik.tu-berlin.de/~wirthig/extrasol/interferometry.html) (in German) that shows how space-based optical interferometry works.