ASTR 1010 1st EditionLecture 12Outline of Last Lecture I. The Doppler EffectA. DiagramB. FormulaOutline of Current LectureI. TelescopesA. DefinitionsB. TypesC. DiagramD. PowerE. InterferometryCurrent LectureI. TelescopesA. Definitions- Light collecting area: telescopes with a larger collecting area can gather a greater amount of light in a shorter time. A telescope’s diameter tells us it’s LCA. Area = (d/2)^2d2¿¿Area= x ¿- Angular resolution: The minimum angular separation a telescope can distinguish. The smaller, or better, angular resolution is found with a larger telescope diameter and smaller wavelengths of light.- Magnification: how much larger the image appears in the telescopes vs the sky- Aperture: diameter of the telescope. The bigger the diameter, the more light it gathers in the same time, so it can see fainter objectsB. Types- Refracting telescope: focuses light with lenses. Focal ratio = focal length/lens diameterMagnification = FL (of telescope)/FL (of eyepiece)Ex. FL (t) = 200cm/FL (e) = 2cm, Mag = 100xProblems: o Heavy glass sagso Glass absorbso Two surfaces to polisho Chromatic aberration: colors focus at different distances- Reflecting telescope: focuses light with mirrorso Only one surface to grind and polisho Support mirror in the back to make it largero No chromatic aberrationo Needs a second mirror to reflect light out of tubeC. Diagram- Types of TelescopesD. Power- Resolving power (RP) = 1diameterSmaller = better- Light Gathering Power (LGP) = D2= AreaLarge Diameters = better, finer detailE. Interferometry- An interferometer combines light from several small telescopes to yield the power of a much larger telescope. The larger the separation, the better the results.- Center for High Angular Resolution Astronomy (CHARA)o CHARA: Long term program at GSU to study tiny details in the sky.o Limited by diameter of
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