Stellar Photometry, Spectroscopy,and Astrophotography in the

Introductory Astronomy Course

T. Olsen & S. TufteLewis & Clark College

Outline

I. History of the Karle Observatory

II. Projects for Advanced Physics Students

III. Observations for IntroductoryAstronomy Students

Outline

I. History of the Karle Observatory

II. Projects for Advanced Physics Students

III. Observations for IntroductoryAstronomy Students

James H. Karle

Sherman Fairchild Initiative• A Proposal to Reinforce Connections

between Science and “Real World” Questions at Lewis & Clark College

• “Research is a Powerful Tool for Attracting and Retaining Students to the Sciences”

• “Discovery-Based Learning from the very first class”

• Biology: Ecological Sampling Equipment, Microscopy Imaging Stations, and Laptop Computers

• Chemistry: NMR Spectrometer and UV/Visible Spectrophotometers

• Physics: Telescope

Moving Day

Telescope Specifications

• 16” Ritchey-Chretien Reflector

• DFM Equatorial Mount

• “The Sky” Planetarium Program Control

• SBIG ST-8XE CCD Camera

• Color Filter Wheel

• Flip Mirror: CCD/Eyepiece

• Self-Guiding Spectrograph

Outline

I. History of the Karle Observatory

II. Projects for Advanced Physics Students

III. Observations for IntroductoryAstronomy Students

Advanced Physics Projects We Have Tried

• Counting the stars in a globular cluster

• Color Astrophotography with a CCD camera

• Taking the temperature of a star with color filters

How many stars are there in the Globular Cluster M15?

Idea:

1. Determine the average number of “counts” (proportional to photons) from stars on the edge where you can resolve them.

2. Measure the total number of counts from the globular. Now divide by the average counts per star to find the number of stars.

Astrophotography with a CCD • The CCD camera is not color sensitive. To make a color

astrophotograph, we – Take separate exposures through filters:

Red, Green, and Blue– Combine them into one color picture using Photoshop

M57: Ring Nebula [Blue Filter]

M57: Ring Nebula [Green Filter]

M57: Ring Nebula [Red Filter]

M57: Ring Nebula

M57: Ring Nebula (zoom)

Finding the Temperature of a Star

€

f ( λ , T ) =

8 π hc λ

− 5

e

hc

λ kT

− 1

Finding the temperature of a star

• Measure the intensity of a star using the red and blue filters

• Calculate the measured ratio of red to blue intensity

• Construct a model using the Planckian distribution including the filter transmission curves and the CCD quantum efficiency to determine the implied temperature of the star.

Other Ideas:

• Take a sequence of pictures of Jupiter over several weeks. Track the position of the moons to get their periods and radii to verify that Kepler’s law applies.

• Measure spectra of stars. Use this to measure the temperature of the star from the blackbody curve, or from absorption lines.

• Measure the spectrum of a nebula. Identify the emission lines of hydrogen and other atoms.

Outline

I. History of the Karle Observatory

II. Projects for Advanced Physics Students

III. Observations for IntroductoryAstronomy Students

Spring 2005

• Evening Viewing Sessions

• Flip Mirror Delivered

Summer 2005

• Instructor masters flip mirror & CCD

• Each Student takes one CCD Image

• Extra Credit: Three Color Image

Fall 2005 …

• Images of Nebulae, Clusters, Planets…

• Estimate the Population of aGlobular Cluster

• Estimate the Temperature of a Star

• Estimate the Distance to a Star by Spectroscopic Parallax

• Test Keplerian Orbits of Jovian Moons