These pages outline how someone not familiar with telescopic observations might go about
using the GTN site to gain a basic understanding of the methods and science underlying the project.
The GTN is not intended to be used in traditional classroom lessons, per se. In fact, it was not created strictly to
be used in classrooms at all. Nonetheless, it can be a powerful resource for students and teachers (as well as others) to obtain an
experience doing real astronomical observations as part of a real research project. While some teachers have used the Network as part
of a high school or college astronomy class, the intention is more that it be used for semester (or longer) science projects or as
part of a semester long observing class. This is because obtaining and then analyzing astroonomical data is a long process. It
cannot always be done in a time frame shorter than several months. However, use of the network is limited only by the imagination,
time and energy of those using it. Here we outline a few exercises and pages to bring you up to speed if you are not an experienced
We have created several web pages on this site that discuss the science of the GTN. These describe in general terms what active
galaxies are and how we study them. You can find links to these pages on the Resources page of our site. In
particular, if you read the sections on Normal Galaxies, Active Galaxies and AGN
Variability you will gain some understanding of the types of objects we study and their relationship to one another.
In addition to active galaxies, the GTN does followup work on gamma ray bursts (GRB); when one of these extremely energetic and
enigmatic objects goes off, many of the GTN telescopes automatically slew to observe it before it fades from view. If you would
like to learn about GRB, you can check out the Imagine the
Universe GRB web site
from Goddard Space Flight Center, a NASA research center just outside Washington, DC. Gamma-ray bursts have only been known for a very
short time. In fact, gamma-ray astronomy itself only goes back a few decades. To get an overview of its history, look over our page on the
history of gamma-ray astronomy.
Several of our pages discuss topics directly related to observational astronomy. Probably the first of these to look at for someone
new to the field is the page on Basic Photometry and Astrometry. On that page we define common
terminology and introduce coordinate systems that are used to describe the locations of objects in the sky and to point telescopes.
To learn the basics of photometry, the process by which the brightness of a star or other astroonomical object is measured, you
should go over the Cookie Cutter Photometry exercise in the GTN Guide. This exercise was developed
here at the SSU NASA E/PO Group and was designed to be used in a classroom or workshop setting. It provides an activity in which
participants model the measurement of an object's brightness. The camera on a telescope does this by using an electronic light
detector called a charge coupled device (CCD); in the exercise participants use playdough and a kitchen scale instead of a CCD, but
the basic notion is the same. The exercise does a nice job of showing how a CCD can be used to measure the brightness of a
star. While a CCD is the light detector found in modern digital cameras, the ones used for astronomy are more sensitive and have
certain modifications that allow them to image extremely faint objects.
A more involved discussion of CCD photometry can be found on our data reduction
page. However, we do not suggest you tackle that until you have familiarized yourself with some of the concepts introduced by
the Cookie Cutter exercise. Working with data from a CCD is computer intensive and requires special software packages,
examples of which are given in the data reduction pages. We are available to provide mentoring for people who would like to work
with data... see the section below on More Advanced Activities.
As we mentioned in the introduction, the GTN was not specifically set up to be used in traditional science classrooms. However, we
have put together several exercises that are designed for the classroom. These introduce some of the science and methodology related
to the GTN in a way that makes it (we hope) more understandable for students and teachers not already experienced making
observations with a telescope.
- Both of the first two exercises can be found in the GTN Guide.
- Cookie Cutter Photometry - The same exercise mentioned in the previous
section. Students use playdough to represent the stars and sky. A kitchen scale represents a light detector. Students are
asked to devise a method by which they may determine the weight of each "star" (weight is a proxy for brightness in this
exercise) without actually putting the star alone on the scale. The exercise includes some background material on CCD detectors
and how they work.
- Jelly Bean Spectroscopy - Like Cookie Cutter Photometry,
the Jelly Bean Spectroscopy exercise uses a simple activity to model an astronomical measurement, in this case
scpectroscopy, in the classroom. Jelly beans of different colors are used as a stand-in for light of different colors. Students
make a histogram of jelly beans, based on their color, in order to learn how spectra are used in astronomy. The GTN does not do
any spectroscopic observations, but we have included this exercise because spectroscopy is of fundamental importance in
astrophysics and other branches of science.
- AGN Flares - Finally, we have created an exercise (still under development) that
asks students to look for relationships between flares seen in active galactic nuclei (AGN) by optical telescopes (like those in
the GTN) and a gamma-ray telescope (the Fermi Gamma-ray Space Telescope, in this case). The exercise uses real observational
data contained in a spreadsheet, so students must use a computer to complete it. Both Mac (iWork '09) and Windows versions are
included. You can download the archive file (3.1 MB) containing the
entire exercise, including written materials and spreadsheets. This exercise introduces one of the basic ways we
learn about AGN, namely doing coordinated observations simultaneously in many wavelengths. These are called multiwavelength (MW)
campaigns and involve many telescopes that span all the way from the radio through infra-red, optical, ultraviolet, x-ray and
gamma-ray. In addition to day to day monitoring of AGN, MW campaigns are one of the primary observing activities of GTN
More Advanced Activities
If you have made it through the materials described above and think you might be up for a bigger challenge, then we encourage you to
sign up with us to be a GTN member. As an associate member we will show you how you can access GTN data, and we
will help you (and your class) learn how to analyze it. If you decide this is what you want to do, you should definitely have a look
at the data reduction page. You will need a computer on which to work with your data. You will also
need some special astronomical software (described on the data reduction page). Most of the currently available software is quite
expensive (more than $100). There is also free software that will do the job, but it has been written by and for professional
astronomers and is not easy to learn to use. We are working on making a data handling system that circumvents these problems.
This page is meant to provide a guide to what you can find on this site and how you might go through it if you are an educator, not an
astronomer, and are thinking astronomical imaging and measurement might be a fun activity for your students (and yourself). If you
have questions, please direct them to Kevin McLin (email at the bottom of this page). We hope you and your students will join us as
we learn about some of the most energetic and exciting objects in the universe.