The Versatile Low Resolution Spectrograph is designed to be used with a Celestron C5 or C8 Schmidt-Cassegrain telescope operating at f/10. The Versatile Low Resolution Spectrograph uses a 25 micron fixed slit, a 250mm focal length collimation lens, (25 mm diameter) and a Paton Hawksley Star Analyser 100 (SA100) grating.

The output of the SA100 grating is viewed with a small telescope for visual use or several types of cameras are used to take images of the spectrum. The cameras used are a Nikon D70 DSLR with 180mmED f/2.8 lens, a Sony Handycam HDR-CX160 video camera and a QSI532 with a 100mm lens.

The below spectrum is of a hand held battery powered five inch fluorescent (Satellite F4T5D) light with the light ten inches in front of the Celestron C8.

The below spectrum is taken with a Nikon D70 DSLR with 180mmED f/2.8 lens.

F4T5D light Specturm With Zero Order, First Order and Part of the Second Order

• The zero order is the white line on the left edge of the image.
• The first order is the colorful spectrum in the center.
• The three emission lines of the second order are very dim on the right side (very dim violet, blue and very dim green emission lines).
• The image has been cropped and resized to 50 percent.
• Horizontal lines in the spectrum are cause by the unevenness of the width of the slit. (tranversalium)

F4T5D light Specturm

• The image is cropped and is at 100 precent.
• The fluorescent light uses excited mercury atoms and therefore the spectrum has strong mercury emission lines
• The bright and colorful mercury emission lines make it easy to identify the wavelengths.
• See the Spectrum of Mercury Gas Discharge for a colorful spectrum diagram that helps to identify the emission lines below.
• Short wavelengths are on the left side of the spectrum and long wavelengths are on the right side of the spectrum.
• 4046.563 Å - violet
• 4358.328 Å - violet.
• 5460.735 Å - green.
• 5769.598 Å - yellow.
• 5790.663 Å - yellow.
• 6149.475 Å - red.
• Horizontal lines in the spectrum are cause by the unevenness of the width of the slit. (tranversalium)

Spectrum Processing

• Spectrum processing was done with RSpec.
• Seven pixel values and wavelenghts were used.
• The 3rd order curve fit gave the best RMS of 4.0690.
• 1st order RMS = 13.8849
• 2nd order RMS = 6.6387
• 3nd order RMS = 4.0690
• 4th order RMS = 4.5799

Calibrated Spectrum Violet-Blue Region

• It is impressive that the two blue emission lines of 4347.494 Å and 4358.328 Å (10.834 Å apart) are separated.

Calibrated Spectrum Green-Yellow Region

• In the area of the 5460.735 Å green emission line I need to check and test the camera setting to determine if the camera is sharpening the image in the camera.
• The two yellow emission lines of 5769.598 Å and 5790.663 Å (21.065 Å apart) are clearly separated.

Calibrated Spectrum Red Region

• Nikon D70 DSLR is a standard camera with poor red to IR response.

Spectrum Measurements

• The start of the spectrum is at 1649 pixel with a wavelength of 4,002.78 Å.
• The end of the spectrum is at 2365 pixel with a wavelength of 7,341.37 Å.
• Therefore, the average wavelength dispersion = (7,341.37 Å - 4,002.78 Å)/(2365-1649 pixels) = 4.66 Å/pixel.
• The spectral resolution is the FWHM which is 12.32 Å at 5,769.15 Å.

Mercury Spectra and Other

• NIST Strong Lines of Mercury (Hg)
  • NIST Atomic Spectra Database
• Spectrum of Neon Gas Discharge Joachim Köppen Strasbourg/Illkirch/Kiel
  • Spectra of Gas Discharges Joachim Köppen Strasbourg/Illkirch/Kiel
• Spectral Elements Chart University of Oregon
• SPECTRAL CALIBRATION by Christian Buil
• Spectra Samples of Mercury by I.N. Galidakis
• How to Measure Spectral Resolution and Wavelength Accuracy by LightForm

© 1998-2012 David Haworth