Kinesthetic Telescope The handout and teacher information is at http://www.cfa.harvard.edu/se uforum/iyacosmos/activities/Ki nestheticTelescope.pdf

http://www.cfa.harvard.edu/seufor um/iyacosmos/ http://www.cfa.harvard.edu/seufor um/iyacosmos/activities/

Telescopes

• Common misconception is that primary purpose of a telescope is to magnify. • Most important purpose of a telescope is to have a large light gathering area - like increasing your pupil size - so you can see dimmer things. • This exercise is for a simple reflector - not the Galileoscope. Galileoscope uses lenses - no mirrors.

Simple reflector

• • The telescopes used by “Observing with NASA” are similar to this http://mo-www.harvard.edu/OWN/ • The design here is called a Herschelian http://en.wikipedia.org/wiki/Reflecting_telescope

Detector:

Labeling the telescope

Mirror focuses all light electronic/CCD or from large aperture to eyeball. Shutter is small detector before detector not pictured here This width is the aperture - the open end of the telescope Blue and green lines are different light rays or particles or waves as they pass through the aperture to mirror and detector

Assign roles to students

• o Light: travels from objects in space to the telescope (have many) • o Aperture: lets the light into the telescope (at least 2 to show edges) • o Mirror: focuses the light toward the detector (one or more holding a piece of cardboard to indicate reflecting surface) • o Shutter: lets the light through to the detector (one to open close) • o Detector: records the light to create an image (one holding a photo - but not revealed until shutter closed) • Also need ‘object in space’ - perhaps bigger photo of same object

Activity is simple

• We are going to talk about some extensions and details that are appropriate for high school level students

From the activity manual

• Notice how light goes in all directions from object in space. • Notice that even some light rays pointing towards earth will not enter telescope - can use to discuss why larger aperture is more preferred.

Shutter

• If the shutter is closed - no light will reach the detector. The longer the shutter is open, the longer the ‘exposure time’, the more light that reaches the detector

Mirror

• The mirror is not flat but acts to focus the light on the detector (like a lens does). You can simulate this by having two ‘light’ rays go to different sides of the mirror through the aperture, but both end up at detector (if shutter open!)

Color vs. Black and White

• Most astronomical cameras are black and white only register presence or absence of light • Can introduce filter wheel before or after shutter • Need to do an activity where they see white light through a filter to show only one color passes through – The Single Bulb simulation from http://phet.colorado.edu/en/simulation/color-vision is great for this if you don’t have white light and cellophane or other filters • Can have 3 black and white images (maybe even the three you got from the OWN telescope!!) showing Red, Green, Blue filtered images • Then leads to making 3 color images in ds9

Detector Resolution

• A further extension is resolution of detector - most teens understand more mega pixels is better but if ‘expand detector’ can show that two light rays with similar paths can end up in same CCD pixel on small detector but end up in two different pixels on larger. • Can draw a grid of 4 pixels vs. 1 pixel in same size area of detector

Pixel Size makes a difference

• “Consider a projected image of a circular object that has a diameter smaller than a pixel. If the image falls directly in the centre of a pixel then the camera will reproduce the object as a square of 1 pixel. Even if the object is imaged onto the vertices of 4 pixels the object will still be reproduced as a square only dimmer - not a faithful reproduction.” http://www.andor.com/learning/digital_cameras/?docid=319