Astronomy 1010-HFall_2015Day-21

Planetary Astronomy

Course Announcements• How is the sunset/sunrise observing going?

• Dark Sky nights – Wed. 10/7 starting at 7:30pm – at the Observatory.

• Exam-2 will be Friday, Oct. 9; Ch. 3, 4, & 5

• SW-chapter 5 posted: due Fri. Oct. 9

• No lab next week – Fall Break

Since the eye already has a lens, the eyepiece is needed to bring the light rays back to parallel for the eye to see

Built in the late 1890’s, it is the last great refracting telescope.

This applies to camera lenses, your eye, telescopes and anything else that uses a lens to focus light

The compound lens takes two lenses of different materials and combines them to correct for color distortion

Since it is meant to be separated we don’t call it an aberration. Instead, it is called dispersion

Diffraction is much more efficient at separating light into its colors than dispersion

Look closely enough at stars and they aren’t just points of light but rings, too

They are large and bulky and difficult

to maneuver

They suffer from chromatic aberration

Even the best glass cuts off the IR and UV wavelengths

Reflecting telescopes use mirrors. There are primary and secondary mirrors. Focal length is determined by the path the

light takes reflecting off the mirrors.

Reflection is the bouncing of light off a surface

ri

Mirrors do not suffer from chromatic aberration and they do not cut off long or short wavelengths

Telescope mirrors are made so that the focus is a plane instead of a point

Definitions & Terms -1• Photon: A particle of light.• Spectrum: The flux of an object as a function of

wavelength.