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Using the Rainbow Optics Star Spectroscope for Visual Observing Paul Bakke.

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Presentation on theme: "Using the Rainbow Optics Star Spectroscope for Visual Observing Paul Bakke."— Presentation transcript:

1 Using the Rainbow Optics Star Spectroscope for Visual Observing Paul Bakke

2 Items to discuss: How Rainbow Optics Star Spectroscope works for visual observing Optics used Objects observed First attempts using a camera with the Rainbow Optics Star Spectroscope

3 Standard eyepiece Diffraction grating cell Cylindrical lens Grating cell mounted to eyepiece

4 Optical Considerations Spectrum width proportional to Exit Pupil –Best: 2 to 3 mm (useful range 1.5 to 4 mm) Spectrum length controlled by: –Eyepiece magnification –Distance from grating to eyepiece lens Exit Pupil = Eyepiece Focal length Telescope f-ratio Longer eyepiece focal length Shorter spectrum Wider spectrum

5 Grating mounted to star diagonal Increases length or “dispersion” of spectrum

6 My setup: 10-inch, f = 10 SCT 25 mm eyepiece

7 Photo taken with hand-held Canon Power Shot at ¼ sec, f3.5, 1600 ISO

8 Source: Jack Martin, London, England 12-inch Dobsonian with Rainbow Optics Star Spectroscope (2-piece model) Photo adapted from

9 Method: Center spectrum in field of view Turn off siderial drive Take “long” exposure photo (< 30 sec.), just enough to “smear” the image Rotate and crop using software

10 Bonus: Use graphics software to make intensity vs. color histogram Paint Shop Pro

11 What to observe First-magnitude stars (using cylindrical lens) –Main-sequence (class V) stars are best –Giants & supergiants have less prominent absorption lines, –Cooler spectral types are good even at larger luminosity class Spectacular: Vega (A0 V), Sirius (A1 V), Betelguese (M2 I)

12 Absorption lines Hot (type A, B) stars: –Hydrogen beta, gamma (blue) are easy –Hydrogen alpha (red), delta (violet) are difficult In type G & cooler stars: G (blue – CH molecule), D (orange – Na), b (green- Mg) Molecular bands (TiO) in M stars

13 More challenging Wolf-Rayet stars (type WN, WC) –Emission lines (blue) –HD in Cygnus (illuminates Crescent Nebula, NGC 6888), mag. 7.7, type WN6 –HD in Cygnus, mag. 8.2, type WC7 Fact: ~½ of all Wolf-Rayet stars brighter than magnitude 9 are in Cygnus!

14 More challenging Carbon stars: absorption bands in blue & violet due to carbon molecules –Y Canum Venaticorum (“La Superba”) –U Hydrae –19 Piscium

15 Rainbow Optics Star Spectroscope Spectroscopy at its most inexpensive & “low tech” Pleasure of visual astronomy Simple photographic possibilities Activities in light-polluted or moonlit sky

16 HAVE FUN!


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