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Transcript
Chapter 3 Stars 3A-1 Gnomon – a pole, column of stones, pillar, or pyramid (like a crude clock or calendar) Uses: -Tell time of day (movement of shadow) -Tell time of year (by length of shadow) -Show motion of heavenly bodies 3A-2 Refractor Telescopes •Use lenses •Objective lens refracts (bends) light •Ocular or eye piece lens focuses & magnifies image 3A-2 Refractor Telescopes Functions of a Telescope 1. Light gathering 2. Magnification: make it bigger 3. Resolution: make it clearer *many stars seen with naked eye are actually 2 or more stars Chromatic Aberration Color distortion due to using lenses to refract light Happens because different wavelengths of light bend different amounts and focus on different points Chromatic Aberration Solutions Use very thin lenses that don’t bend light much (makes telescope very long) Use a compound lens (one convex & one concave) cemented together Chromatic Aberration Sir Isaac Newton discovered white light is made of many colors (each with a different wavelength) His solutions was to use mirrors instead of lenses Homework: SRQ 3A-1 BELL WORK •What is a gnomer? * Please answer this question in your own words (Don’t just copy a definition from your notes.) 3A-3 Reflecting Telescopes •Developed by Newton •Use mirrors •Ex: Newtonian Reflector & Cassegranian Reflector 3A-3 Newtonian Reflector •Has concave mirror, flat mirror, & eye piece •Image is viewed from the side 3A-3 Cassegranian Reflector Light enters, reflects off large concave mirror with hole in center Reflects to a convex mirror, which reflects through the hole to the ocular Advantage: compact design Mirrors & Telescopes Telescopes with mirrors can be built much larger than lenstelescopes - Some 10 m in diameter! - No aberration if shaped in parabolic curve Mirrors & Telescopes 3 Advances in Mirror Design (made mirrors larger than 5 m possible) 1. Honeycomb mirror – reduces mirror weight by spincasting 2. Segmented mirrors – smaller pieces fit together to make large mirror 3. Meniscus mirror – very thin & controlled shape by computerized actuators Composite Telescope Uses mirrors & correcting lens objective Gives fine detail over a wide field - Ex: Schmidt telescope *Be able to diagram all 4 types of telescopes in 3A-2 & 3A-3 3A-4 Non optical telescopes •Do not use visible light •Study other waves given off by stars (Radiowaves, infra red, ultra violet, gamma & x rays) • Atmosphere blocks most of these, but does not block radio waves Non optical telescopes •Radio telescope: - Has large, dish shaped antenna - focuses amplifies & analyzes radio waves from space - Can send radio waves (as radar) - Separate radio telescopes can work together Non optical telescopes Other telescopes *placed above earth & can see things filtered out by atmosphere Chandra x-ray telescope Hubble Space Telescope (HTS) Placed in orbit in 1990, has optical & non optical equipment Can “see” things hidden behind dust, takes pictures, transmits them to earth Telescope Mounts • Must be able to move vertically & horizontally to point in any direction • Altazimuth mount: has separate vertical & horizontal controls • Equatorial (German) mount: Telescope tube rotates around attached pole, pole points to celestial pole • Dobsonian mount: useful for amateurs, has a turn table on the ground and is a modified Altazimuth Recording telescope images • Optical telescope: Image recorded by camera & photographs • Non-optical telescope: Computer turns strip chart/digital data into picture • Main star charts & catalogs • 1. hipparchus catalog • 2. Tycho-2 catalog (2.5 mil. stars) Keeping track of star data •Main star charts & catalogs •1. Hipparchus catalog •2. Tycho-2 catalog (2.5 mil. stars) Homework: SRQ 3A-2 (all) SRQ 3A-3 (1-6) Study for Quiz 3A