Topic 11 telescopes Flashcards
(32 cards)
simply, how do telescopes work
have a lens, mirror or both to enlarge images by collecting light
lens/mirror place at end of tube, light is magnified/reflected to an eyepiece which shows an enlarged image of what is being viewed
what are the 2 types of telescope
refractor, reflector
describe refractor telescope
convex lens used at end of a tube to bring an image into focus at a point
-another lens called an eyepiece is used at the opposite end of the tube to magnify the image
what is convex lens made of
glass coated in a film to allow less light to be reflected and more to pass through the lens
give 2 examples of refracting telescopes
GALILEAN
KEPLERIAN
give features of galilean telescope
-uses concave lens aa eyepiece
-typically fixed focus
-has limited field of view
REFRACTING
give features of keplerian telescope
-uses convex lens
-larger and heavier than galilean
-focusable
-images are inverted
REFRACTING
what are the 2 reflector telescopes
newtonian
cassegrain
give features of newtonian reflector
-concave mirror reflects light
-focuses by secondary mirror further up tube @ 45 degree angle
-magnified using eyepiece
give features of a cassegrain reflector
reflects loght from concave lens to seco dary mirror
-this mirror is facing primary mirror, reflectes light back down toward sprimary but focuses through a small hole behind primary
what is a reflector’s mirror usually made of
glass with an aluminium coating
give 3 reasons why reflectors have gained popularity over refractors
-higher resolution can be achieved with a smaller tube
-refractors suffer from chromatic abberation (colour can be warped)
-refractors suffer from lens sagging
-refractors have a maximum size of 1 metre wide
define aperture
amount of light the telescope receuves (larger lens/mirror=higher aperture)
what does aperture determine
how well we are able to see fainter objects
what is light grasp
kight-gathering power
-measure of telescope’s ability to capture light and is directly related to size of instruments main lens/mirror
what is light grasp directly proportional to
area of objective element and thus the square diameter of ovjective element
true fov=?
apparent fov/magnification
define resolution
how a telewcope will shwo the detail of an object being observed
how can you increase resolution
increase aperture size
what else determines the resolution
-diffraction of light caused by atmosphere
-wavelenght
-quality of telescope
-contrast
-brightness
-observer’s quality of eyesight
what is another phrase for a telescope’s resolution
angular resolution
or
resolving power
formula for resolution
wavelength/diameter
what did galileo discover
jupiter’s four large satellites
moon’s uneven surface
venus’ phases
sunspots
what was galileo the first to do
he was the first telescopic observer to make published astronomical observations
