angular resolution and sorting

Angular resolution:

• We can rearrange into what is known as rayleigh criterion for angular resolvability-the smallest angular distance between two objects for us to resolve them for a given “d”

• An example of this limit is pointillism, where by paining dots cannot be seen at a distance but can be seen up close

As the light comes through the telescope it bends bc of refraction 

Sorting: 

• depending on the objective, the light entering the telescope ma be split, sorted by wavelength and order

• This may be done physically or through a computer

• Some of the light might be sent out on instrument while the rest is sent to another

• Each one of these instruments is a different form of detector

Detector

• Anything that sees the light and measures some characteristics

• Camera, ccd, spectrometers ect

Telescope-light gathering power

• Light gathering power is just the amount of light collecting area

• area=

• A 2 meter diameter telescopes gather four times as much light as a 1 meter telescope

Magnification:

• Want to get it as light and bright as possible, best way to do that is get the lens as big as possible 

mag= focal length/focal eyepiece 

19.2/0.1=192 magnification 

James webb is a reflecting telescope, it has the reflection of the NASA logo on it

Wednesday february 26th:

Diffraction: the spreading or fanning of waves through an opening or around object

The smaller the opening the greater the flare, the hole is within an order of magnitude of the wavelength 

How does angular resolution work in astronomy:

Several telescopes connected to act as one- interferometer

Rainbow-making effect-chromatic aberration

Smearing effect due to sharp edge-diffraction 

Distance from lens to focal plane-focal length

Diameter-aperture

Ability to distinguish objects that appear close together in the sky-resolution

Collecting light- photography

• Opened the door to modern astronomy

• Images could be captured on photographic plates

• Increased integration time comes with longer exposures

• Photographic plates were expensive and slow

Collecting light CCD charge coupled device

• CCDs charge coupled devices (such as digital cameras)

• Electronic detectors record photons on pixels

• Photons create a signal in the array

• The electronically recorded images can greatly exceed photographs in quality

• CCDs are the astronomers detector of choice

Spectrographs

• They disperse the incoming light into its component wavelengths

• Spectrographs let astronomers study the spectrum, of an object's light 

• 
  

  

• The atmosphere does not transmit all light

• Nearly all X ray ultraviolet and infrared wavelengths are blocked

• Space based telescopes are needed for theses wavelengths 

Radio telescopes are large parabolic dishes with antennas.

• They allow astronomers to study radio waves with wavelengths of a centimeter to about 10 meters

• Radio waves can pass through gas and dust 

• Single radio telescopes have poor resolution due to the long wavelengths 

• Interferometric arrays combine the signals from many telescopes increasing effective diameter size, which increases resolution

• The square kilometre array will have thousands of telescopes built in australia and south africa by 2024