Constellation
a group of stars that form a recognizable pattern that is named after
its form or mythological figure
Gnomon
a tool used to serve as a crude clock and calendar to aid astronomers
in judging the motion of the sun and stars
Quadrant
a tool used to take angular measurements of altitude in astronomy
Roger Bacon
an English philosopher who was one of the first to investigate the
use of lenses
Refractor Telescope
uses lenses only to magnify and image. it bends light from a star or
planet to make it appear larger and closer.
Objective Lens
gathers the light
Ocular (eyepiece) Lens
magnifies
Resolution
the ability of a telescope to bring out details in an image
Wavelength
the angular distance from one wave crest to the next wave crest
Chromatic Abberation
color distortion (a serious problem with refractors)
Compound Lenses
two or more lenses made of different kinds of glass mounted together
to correct for chromatic abberation
Reflector Telescope
replaced the refractor's light-gathering objective lens with a mirror
Newtonian Reflector
viewed from a position on the side of the telescope
Cassegrainian Reflector
its large concave mirror reflects light to a convex mirror fixed in
the center near the front of the tube
Composite Telescope
uses both mirrors and a correcting objective lens to gather light
Schmidt-Cassegrainian Telescope
uses both a lens and a mirror
When is it probably that people first studied stars and grouped them
into constellations?
before the flood
What was the gnomon called when a number dial was added to it?
a sundial
What are the three functions of a telescope?
1. light gathering
2. resolution
3. magnification
What does a refractor telescope use to accomplish these three functions?
lenses
Give to ways to reduce color distortion
1. use thin objective lenses that don't bend light
2. use compound lenses which focus colors
Radio Telescopes
a radio receiver with a large dish-shaped antenna system
Hubble Space Telescope (HST)
spans the optical and non optical categories of telescopes