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Unformatted text preview: Spectrograph Optics: 12:45 — 1:10, 25 min • Collimated beam at grating, or beam and dispersion angles mixed • Review of making a spectrum from an image • Input image now smeared in λ • R determined by PSF size: “true” spectrum convolved by PSF • BUT, we can pass light through a slit to reduce PSF 1 • Spectrograph optics – Discard light, but improve R – Avoid nearby objects contaminating spectrum – Can use mirrored slit, send rest of image to slit-viewing camera – Camera can guide exposure – Camera can monitor slit placement 4 Long-Slit Spectroscopy: 1:10 — 1:25, 15 min • 14specextract • Slit usually covers entire detector (why else?) • Star is only part of the slit • Can get sky background spectrum next to star • Extended objects bigger, may or may not fill slit • Scan slit: spatial-spectral hypercube • Can also allow planet to rotate under slit 2...
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- Fall '09
- Astronomical, 15 min, 10 min, median combination