Conversion to wavelength
• Function to convert pixel values to wavelength uses the equation:
• Calibration completed for Helium and Cadmium so far (Below are some examples of the values used for the function of lambda):
 Filename Micrometer setting Peaklocation Wavelength Calib_He_0100 1.00 145.582, 690.276 728.1, 778.3 Calib_He_0150 1.50 174.077, 403.700 706.5, 728.1 Calib_He_0200 2.00 33.349, 433.886, 668.112 668.7, 706.5, 728.1 Calib_He_0250 2.50 289.445, 699.538 668.7, 706.5 Calib_Cd_0550 5.50 0.0299, 110.860, 380.483 467.945, 480.125, 508.724 Calib_Cd_0600 6.00 262.870, 377.610, 651.768 467.945,480.125,508.724 Calib_Cd_0650 6.50 530.697, 646.576 467.945,480.125
• The cut off value (wrt the second derivative) for a fluctuation to be considered a peak was: -0.05.
• If the x range was greater than 2 than it was considered a peak.
 Parameter Initial guess values Output values
• Relation between wavelength and micrometer position for pixel postion of 3.50mm:

• Plot of pixel to wavelength conversion. Lower micrometer settings the output wavelength values would be: than the actual wavelengths.
• Higher micrometer settings the output wavelengths would be greater than the actual wavelength by:

• Test Helium plot for micrometer setting of 6.50mm:
Fitting to observation data

• Gaussian equation used:
• where a is amplitude, μ is the mean of the distribution, σ is the standard deviation of the curve and b is the background

• Cauchy - Lorentz equation used:
• where a is amplitude, μ is peak position, γ is the HWHM and b is the background

• For a pixel range of plus minus 100 pixels of the estimated μ and with the same guess parameters passed to each function, the following fits were obtained
• Gaussian fit to the peak in Vega, centered at 6.00mm:
• Chi squared of ~338345

• Lorentzian fit to the peak in Vega, centered at 6.00mm:
• Chi squared of ~278812
-- WillBurrows - 24 Jan 2017
Topic attachments
I Attachment Action Size Date Who Comment
png Helium_0650.png manage 78.3 K 25 Jan 2017 - 09:31 JamesAngthopo Test Helium plot for micrometer setting of 6.50
png Helium_0700.png manage 67.0 K 25 Jan 2017 - 09:43 JamesAngthopo Test Helium plot for micrometer setting of 7.00
png Micro_waverelation.png manage 36.1 K 25 Jan 2017 - 09:30 JamesAngthopo Relation between wavelength and micrometer position for pixel postion of 350
png Vega_0600_180_gauss.png manage 57.4 K 24 Jan 2017 - 20:21 WillBurrows Gaussian fit to the peak in Vega, centered at 6.00mm
png Vega_0600_180_lorentz.png manage 48.3 K 24 Jan 2017 - 20:20 WillBurrows Lorentzian fit to the peak in Vega, centered at 6.00mm

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Topic revision: r4 - 25 Jan 2017 - JamesAngthopo

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