Basics of Telescopes Quiz

The focal length of the eyepiece.

Plane wavefronts diffract upon encountering the circular aperture, and focus as an Airy disk.

They produce interfering Airy patterns.

<p>It moves the individual maxima around the image plane to produce a large seeing disk.</p> Signup and view all the answers

<p>As a series of plane-parallel plates, and the surface as an infinite plane.</p> Signup and view all the answers

<p>It curves the path of the incident ray.</p> Signup and view all the answers

<p>In a Cassegrain reflector, the focus is behind the primary mirror ($\beta$ is positive).</p> Signup and view all the answers

<p>For a Cassegrain reflector, $m$ and $k$ are both positive, while for a Gregorian reflector, they are both negative.</p> Signup and view all the answers

<p>The classical Cassegrain and Gregorian reflectors assume the primary mirror must be a paraboloid, resulting in coma and astigmatism, while the aplanatic two-mirror telescopes can use any conic constant for the primary and find a secondary shape that preserves freedom from spherical aberration.</p> Signup and view all the answers

<p>The aplanatic Cassegrain is called the Ritchey–Chretien (R–C) design, and consists of a hyperbolic primary and hyperbolic secondary mirror.</p> Signup and view all the answers

<p>The tube of the Cassegrain reflector will be much shorter than a Newtonian reflector of the same focal length.</p> Signup and view all the answers

<p>The overall focal length, $f$, is positive for a Cassegrain reflector and negative for a Gregorian reflector.</p> Signup and view all the answers

<p>Redirect light from the secondary mirror along the hollow altitude axis</p> Signup and view all the answers

<p>By a series of flats to bring the beam to the polar axis</p> Signup and view all the answers

<p>Produces good images over a much larger field (6 to 8 degrees)</p> Signup and view all the answers

<p>By exploiting the symmetry of a spherical mirror</p> Signup and view all the answers

<p>Spherical primary mirror, aperture stop, refracting corrector plate</p> Signup and view all the answers

<p>6 to 8 degrees</p> Signup and view all the answers

<p>To remove wavefront distortions caused by atmospheric turbulence.</p> Signup and view all the answers

<p>Near the telescope focal plane.</p> Signup and view all the answers

<p>Reflective elements.</p> Signup and view all the answers

<p>To exactly cancel the distortions generated by atmospheric turbulence.</p> Signup and view all the answers

<p>Determining the wavefront distortions to apply corrections.</p> Signup and view all the answers

<p>It is a disclaimer about the usage and distribution of the presentation.</p> Signup and view all the answers

<p>The wavefront aberration of coma depends on the formula $\rho^3 b \cos \phi$.</p> Signup and view all the answers

<p>Like spherical aberration, coma is particularly a problem of large apertures.</p> Signup and view all the answers

<p>An aplanatic optical system is one with neither spherical aberration nor coma.</p> Signup and view all the answers

<p>No, a single-element aplanatic telescope, either in a refractor or reflector, is not possible.</p> Signup and view all the answers

<p>Minimizing coma in refracting systems requires a system of lenses, and achromatic doublet or triplet designs that minimize spherical aberration also reduce coma.</p> Signup and view all the answers

<p>The wavefront distortion of astigmatism depends on the formula $\rho^3 b^2 \cos^2 \phi$.</p> Signup and view all the answers