Astro 1 - Lecture 8


Matthew A. Bershady

Department of Astronomy & Astrophysics

Penn State University


Fall 1996

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© 1995 Matthew A. Bershady

Lectures Lecture page Astro1 page


LIGHT BUCKETS


1. Types of Telescopes


Why build telescopes to gather light at different wavelengths?

Do different types of telescopes have to be built to gather light at different wavelengths?

Constraints:



2. Diffraction limit

diffraction: (arcsecond) = 2.5x105 /D

= wavelength

D = telescope diameter



3. Instruments

Imagers -- cameras, to take pictures

Spectrographs -- to take spectra

both use:

Detectors -- most often today, a CCD

CCD = Charge Coupled Device

pixels



4. Techniques

Adaptive optics -

Correct for atmospheric blur, ``seeing'' by deforming the mirror to compensate for atmospheric distortions

Interferometry -

Use an array of telescopes to synthesize a larger aperture.

This reduces the diffraction limit.



Q8.1 If a telescope's spatial resolution is not diffraction-limited, which of the following will increase (improve) the spatial resolution?

(a) building a bigger telescope

(b) observing below the atmosphere

(c) observing at shorter wavelengths

(d) use a CCD with bigger pixels

(e) using adaptive optics

Q8.2 What is the novel new mirror design that has allowed astronomers to build 10-meter sized optical telescopes for relatively little money?

(a) refractive optics

(b) reflective optics

(c) monolithic mirrors

(d) segmented mirrors

(e) adaptive optics


Lectures Lecture page Astro1 page
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Last updated: Sep 4, 1996 Matthew A. Bershady