Home Random Page



The Fine Art of Observing

The challenge of astronomy is that we must view most of the universe from extremely far away. When you're trying to see something well on Earth, your instinct is to move closer for a better look. But when it comes to stars and galaxies, we're stuck where we are. So, ever since the dawn of telescopic astronomy, the art of observing has been the art of using your eye to the utmost of its ability.

Looking with care. When looking through the telescope, focus and refocus with care. A good observer is always fiddling with the focus, trying to get it just a hair sharper. Many people find it best to keep both eyes open, since squinting strains the working eye. You can cover the "off" eye with one hand or with an inexpensive eye patch, available at drugstores.

Don't expect to see everything an astronomical object has to offer right away. The first look always shows less than comes out with continued scrutiny. This is true whether your subject is a dim galaxy that can hardly be told from the blackness of space, or a hairline feature on the blindingly bright Moon.

Seeing Through the "Seeing." One reason it takes time to see detail is the unsteadiness of the Earth's atmosphere. Celestial objects constantly shimmer and boil when viewed at high power, thanks to weak but ever-present heat waves in the air around and above us. The severity of this shimmering Ч called the atmospheric seeing Ч varies from night to night and often from minute to minute.

First one detail is noticed and fixed, and you think there's nothing more to be seen. But after a few minutes another detail becomes evident, then another.

To convince yourself of this, look at a piece of sky with the naked eye and try to spot faint stars. Some will be visible right away; others take a few seconds to come out. When no more appear, most people would quit trying. But keep at it for a few minutes.

The planet Mars provides another classic example of this effect. For the beginner taking a first look with a small telescope, Mars ranks as the most disappointing object in the sky. It's just a tiny, featureless, orange fuzzball. The beginner steps aside to let an experienced Mars observer look in the eyepiece. Silence. "There's the north polar cap. . . . That big dark area in the south must be Mare Erythraeum. Okay, I've got Sinus Meridiani. . . . There's a cloud patch on the western limb. . . . "

The beginner looks again. Nothing but a fuzzball.

Training Your Eye. An excellent way to train yourself to see better is to make sketches. These don't have to be works of art; the idea is just to record details in your notebook more directly than you can with words. Star fields require no artistic talent whatsoever, but by sketching a field that contains a faint asteroid or outer planet, you can identify the intruder.

For practice sketching planets, try drawing the Moon with the naked eye. If you have reasonably sharp or well-corrected vision, the Moon shows much more detail to the naked eye than any planet will in a telescope! Make a semicircle a couple of inches in diameter by tracing some round object and then draw the terminator exactly as you see it on the Moon. Carefully add the major dark areas with pencil shading, then look for finer markings. By now you'll be seeing much more detail on the Moon's face than you ever thought possible without optical aid.

crosshairs (тех.) - крест нитей, перекрестье

3.3.8. What is the Sloan Digital Sky Survey?

Simply put, the Sloan Digital Sky Survey is the most ambitious astronomical survey project ever undertaken. The survey will map in detail one-quarter of the entire sky, determining the positions and absolute brightnesses of more than 100 million celestial objects. It will also measure the distances to more than a million galaxies and quasars. Apache Point Observatory, site of the SDSS telescopes, is operated by the Astrophysical Research Consortium (ARC).

The SDSS addresses fascinating, fundamental questions about the universe. With the survey, astronomers will be able to see the large-scale patterns of galactic sheets and voids in the universe. Scientists have varying ideas about the evolution of the universe, and different patterns of large-scale structure point to different theories of how the universe evolved. The Sloan Digital Sky Survey will tell us which theories are right -- or whether we have to come up with entirely new ideas.

The Sloan Digital Sky Survey (SDSS) is a joint project of The University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, The Korean Scientist Group (KSG), the Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, University of Pittsburgh, Princeton University, the United States Naval Observatory, and the University of Washington.

Funding for the project has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Aeronautics and Space Administration, the National Science Foundation, the U.S. Department of Energy, the Japanese Monbukagakusho, and the Max Planck Society.

Date: 2015-12-18; view: 526

<== previous page | next page ==>
Optical Projection and Direct Viewing | Mapping the Universe 2 page
doclecture.net - lectures - 2014-2018 year. Copyright infringement or personal data (0.002 sec.)