Youth AstroNet Program Introduction This presentation based on information and materials from The Harvard-Smithsonian Center for Astrophysics Science Education Portal Questions about this presentation? Contact Carolyn

What is light? Image credit:

Telescopes Telescopes gather light from a distant object and focus that light into an image. A simple telescope: Image from:

Refracting Telescopes Refracting telescopes were invented by Refracting telescopes use lenses to gather and focus light. The size of the refracting telescope is limited by the size of the lens you can make. Image from:

Refracting Telescopes The largest refracting telescope is the Yerkes Telescope. It is located in Wisconsin and is run by the University of Chicago. The objective lens is 40 inches in diameter; the steel tube is 69 feet long. Image from:

Refraction When light waves change direction as they pass from one medium to another. Image credit:

Refraction Different wavelengths of light slow (or speed up) at different rates in the same medium. Image credit:

Refraction with Lenses Image credit:

Reflecting Telescopes Reflecting telescopes were invented in 1668 or 1669 (by Sir Isaac Newton). Reflecting telescopes use a mirror to gather and focus light and another mirror to direct the light to an eyepiece or camera. Image credit:

Reflecting Telescopes The largest single mirrors telescope ever built is the Large Binocular Telescope, which has mirrors which are 8.4 meters (27.6 feet) in diameter. The Large Binocular Telescope is located in Arizona. Image credit:

Reflecting Telescopes The Keck telescopes in Mauna Kea, Hawaii, have a 10 meter mirror, which is composed of 36 smaller hexagonal mirrors. Image credit: Image credit: The James Webb Telescope will have a 6.5 meter mirror (composed of segments). It is scheduled to launch October 2018.

Reflection When light hits an object and bounces off Image credit: Image credit:

Other Types of Telescopes Reflecting and refracting telescopes are optical telescopes, because they collect visible light. Image credit:

Other Types of Telescopes NASA has telescopes that cover the range of the electromagnetic spectrum. Want to learn more about the electromagnetic spectrum? Go here: gov/ems/ gov/ems/ Image credit: lva1-app6892/95/tour-ofems-bookletweb jpg?cb=

MicroObservatory Telescopes These are the telescopes you will be using. These are OPTICAL telescopes. You will be processing images taken with these telescopes. Image credit:

CCD Camera (“Charge Coupled Device”) CCDs have sensors that convert light into electrical charges. The more intense the light, the stronger the electrical charge. The CCD then “reads” a value of the electrical charge. Image credit: By Andrzej w k 2 - Own work, CC BY-SA 4.0,

Zooming in on a Digital Image

Pixel Each sensor on the CCD is called a pixel. This image is a 1,000X close up of a CCD. Image credit: Image credit: credit: from Nikon Small World

Short Exposure vs Long Exposure Exposure is how long light is allowed to strike the CCD. The more light that the CCD collects, the more detail the final image will have. Image credit:

Over Exposure Some objects are very bright. If you have a long exposure, the CCD may collect too much light and you cannot see contrast. Image credit:

And the Earth is moving… The MicroObservatory Telescopes “track” objects, so we shouldn’t get blurred images. Image source: S07LPAhUCGz4KHZjeCLMQ_AUIBigB#imgrc=vbG3yi1VxBPiPM%3A

How to Process an Image Go to microobservatory.org

Scroll down…Click on YouthAstroNet Portal

Click on YouthAstroNet Activity Portal

Login Enter your username and password

You should be here:

Scroll down… click on MicroObservatory Robotic Tools

Click on Use the images in JS9

Hover on Archived Images On the menu that appears, click on AndromedaGal (first in the list)

Your image should look like this… Important things to notice: Scale Pixel Value Low Brightness Limits Shift/Bias High Brightness Limits Stretch/Contrast

Scale and Pixel Value Hover over Scale. Click on log. Then, move your cursor around the image and try to find the spot with the LOWEST Pixel Value. What is the LOWEST Pixel Value you found?

Linear Scale vs Log Scale On a linear scale, the change in value is based on the difference between the values. On a log scale, the change in value is based on the ratio of the values. For example, linear: the difference between 1 and 2 is the same as the difference between 4 and 5 log: the difference between 1 and 2 is the same as the difference between 4 and 8 Image credit: schoolbag.info

Low Brightness Limits Change the Low Brightness Limits to the lowest pixel value you found. (After you type in the value, press enter on your keyboard.) 280? (top right)

Shift/Bias Use the +/- buttons to shift the color scale so that the parts of the sky you think should be dark are dark (but no so dark that your faint stars disappear).

Shift/Bias There is no right or wrong answer. In the image on the right, I used a shift/bias of 0.70.

High Brightness Limits Try to find the HIGHEST Pixel Value you can. Enter the HIGHEST Pixel Value you find as the High Brightness Limit. 1163? (little right, little down of bright spot)

Stretch/Contrast Use the +/- buttons on Shift/Contrast to get the dark parts dark again. There is no right or wrong answer. In the image on the right, I used a shift/contrast of 2.20.

Color! The MicroObservatory telescopes only “see” white, black, and shades of gray. Sometimes it is easier to pick out details when we add color. Hover over Color and click on Frost.

Shift/Bias? Stretch/Contrast? Adjust your Shift/Bias and Stretch/Contrast settings to create an image you like. There are no right or wrong answers. To save your image in a format you can use (or print), hover over Image and click on Save as PNG.