By

Keith Schlottman

Presented at Texas Star Party 05/16/07

Have You Ever Used Spectroscopy?

Seen a Rainbow?

Used a Nebula Filter?

Viewed the Sun in H-Alpha?

Noticed that Vega is Bluish and Arcturus is Reddish?

The Spectrum Tells A Story

• Stars– Stellar classifications / HR Diagram– Age of star– Surface gravity– Pressure– Surface temperature– Radial velocity– Identify spectroscopic binaries

• Other Objects– Galactic and Quasar redshifts– Nebular compositions– Comets and Planets

Equipment – Visual Spectroscopy

• Prism

• CD-ROM

• Project Star Spectrometer

• Naked Eye (Rainbows & Moonbows)

Equipment – Telescopic Spectrographs

• More Expensive• SBIG SGS• LHIRES III• Baader DADOS• Sivo Scientific Nu-View II

• Moderately Expensive• SBIG DSS-7

• Less Expensive• DG Spectrum Filters• Rainbow Optics Star Spectroscopes• Rigel Systems RS-Spectroscope• Paton Hawksley Star Analyser• Build Your Own

Comparison of 4 SpectrographsSBIG SGS SBIG DSS7 LHIRES III DG1 FILTER

COST $4,950 $1,595 ~ $3,000 ~ $150

GRATING TYPE Reflection Reflection Reflection Transmission

GRATING Lines/mm

150 (Low)600 (High)

100 150, 300, 600, 1200, 2400

200, 500, or 1,000

DISPERSIONAngst./pixel w/ST-7

4.3 (Low)1.1 (High)

5.4 3.0 (Lowest) to0.12 (Highest)

Up to 0.5

RESOLUTIONWith ST-7

9Å (Low)2.4Å (High)

16Å Up to 0.4Å Varies

λ RANGE Tuneable Fixed Tuneable Fixed

GUIDING Internal or External

None or External

Separate or External

Internal or External

BEST FOR Stars, Nebulae

Nebulae, Galaxies

Stars Stars

Information based on my experience and manufacturer claims, may not be 100% accurate

Acquiring Data With the SGS

• Use CCDSoft

• Guide on Slit

• Binning 1x4

• Note that images are monochrome!

Processing Data

• Dark Subtract, Median Combine (CCDStack)• Rotate if Low-Res Mode (IRIS)

• Wavelength Calibration (vSpec)• Flux Calibration for CCD Response (equivalent

to Flat Field)

Wavelength Calibration - HEdmund Scientific

Lamps are used

Spectral Types

Spectra taken with

The SBIG SGS on a 12”

LX-200GPS from my

Tucson backyard on

October 16 & 17, 2006. RE

D

BL

UE

Identifying Stellar Composition

Emission Nebula

The OIII emission lines were thought to be a new element in the early 20th century, “Nebulium”.

Emission Nebulae

Pla

nets

Com

ets

Nov

ae

Var

iabl

e S

tars

Pro-Am Collaborations

Amateur spectroscopists were asked to obtain data on this star, which was a target for the COROT satellite.

Be

Sta

rs

You

ng S

tars

T T

auri

A very young star, still undergoing contraction.

Tex

as S

tar

Par

ty 2

007

Blueshifted absorption feature provides a basis for calculating radial velocity of the expanding shell.Preliminary calculation from this data is~ 200 km/sec.

This data was obtained early Monday morning at TSP Upper Field.

DG Spectrum Filter

• Zero and First Order on Main Chip

Vega

• Use Known Lines to Calibrate in vSpec

The Easiest Spectrum to Observe –No Equipment Necessary!

For more information see: http://www.xanaduobservatory.com