Developing a Littrow Spectrograph

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Developing a Littrow Spectrograph
Mary Masterman Westmoore High School University
of Oklahoma
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Purpose of Littrow

• Study Spectroscopic Binary Stars
• Study Zeeman Splitting
• Popularize spectroscopy by enabling amateur
  research
• Study Vibrational Spectroscopy through Raman
  Effect (applications to planetary science)

Glass
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How Gratings Work
The Double Slit Experiment
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Why Does This Happen?
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(No Transcript)
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What Happens
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What Happens
http//www.src.wits.ac.za/pages/teaching/Connell/p
hys284/2005/lecture-02/lecture_02/img21.png
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The Double-Slit Experiment With Different Colors
-1st
1st
-2nd
2nd
 Graph from Scott Hesser. Photo from
http//www.thespectroscopynet.com/Educational/Diff
raction.htm.
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Transmission Grating
Camera (or Screen)
Transmission Grating
-1st Order
White Light
0th Order
1st Order
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Reflection Grating
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2004 38 classical spectrograph
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38 Classical Spectrograph
Disadvantages Long, heavy, stuck out from
telescope Low Resolution longer lens
needed Solution Try Littrow Configuration Theory
Christian Buil, France
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New Spectrograph 2006
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Light path side view
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Light Path top section
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Designing the Littrow Spectrograph
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Fabricating Body
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Body/ Mirror
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Grating Holder
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Adjustable Slit
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Camera Mount
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Aligning Spectrograph
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Using on Telescope
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Solar spectrum
Solar spectrum w/ Fraunhoffer lines
Intensity (ADUs)
Wavelength (Angstroms)
Camera Canon Rebel DSLR (no Telescope)
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M42 Nebula
NII Ha NII
SII
Neon calibration spectrum
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0th Order- center image on slit
M57 30cm f/10 telescope 60 sec exposure
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M57 Spectrum near H?
H?
OIII OIII
Vega H?
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M57 Spectrum near H?
H?
NII NII
SII SII
OI
OI
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Visual Spec Program
Mercury Lamp Spectrum

• VSPEC (France) is freeware by Valerie Desnoux.

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Crop The Image
After acquiring the image, the desired spectrum
must be cropped from the raw image.
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Conclusions

• A bigger telescope with better polar alignment is
  neccesary
• Higher dispersion gt Decreased range gt
  Frustrating compared to classical spectrograph
• Cost 350 Relatively cheap - Benefit