Vega Spectrum Angstroms Calibration Without Zero Order by RSpec Image August 2, 2011 at 11:00 am PDT
The above image is the
star
Vega (Wikipedia).
The round spectral order zero is on the left side of the image and its first order blazed
grating
spectrum is on the right side.
This web page shows how
Field Tested Software RSpec V1.3.0 (Build: 39)
nonlinear Calibration Wizard was used to calibrate the horziontal axis in angstroms (Å) and shows the results of not including the zero order using the four different curves (1st, 2nd, 3rd and 4th).
Below each spectrum is the Calibration Wizard window with the five residuals that are in angstroms and the
RMS
for that order. Residuals equal to zero are ideal and RMS equals to zero is ideal.
Below is a summary table of the residuals and RMS value calculated in Excel VegaA06012s06cropRMS.xlsx for both with and without the zero order. This web page shows the details of the calibration without the 0 order. This is the table on the right. Click on the table on the left to see the details of the calibration with the 0 order.
To put the values of the residuals in perspective the difference between CCD camera pixels at Hα is approximately 17.9 Å when using fourth order calibration without the zero order.
 The first order calibration which is linear has the Hα, Hβ and Hγ looking good on the spectrum chart. Hδ, Hε and Hζ absorption lines are at the wrong wavelength. Using RMS the first order calibration falls between the second to third order calibration using the zero order.
 The second order calibration improves the Hδ, Hε, Hζ, Hα and A(O_{2}) absorption lines. Hβ and Hγ absorption lines are worse than first order.
 The third order calibration improves Hβ, Hα and A(O_{2}) absorption lines. But, Hγ and Hδ are worse than second order calibration.
 The forth order calibration has slight improvements over the third order calibration. There is very little difference between third order and forth order calibration looking at the spectrum chart. The forth order has the lowest RMS values with 0.00 (RSpec) and 2.84 (Excel).
 The spectrum chart vertical axis is the intensity values of the spectrum image.
 The red + are measured data points.
 The spectrum chart horizontal axis is wavelength in angstroms (Å).
 Reference yellow line markers show hydrogen Balmer absorption lines (Hα, Hβ, Hγ, Hδ, Hε and Hζ),
Fraunhofer
telluric
O_{2}
absorption bands and
telluric H_{2}O absorption band.
 Telluric H_{2}O band is 7168 Å to 7394 Å
(Table 95, page 100,
Spectroscopic Atlas for Amateur Astronomers, Verson 2.0 by Richard Walker)
 Below the spectrum chart is a synthesize color spectrum generated from the spectrum chart data.
 Data files in VegaA06012s06crop4orderNo0.zip
 Spectrum image VegaA06012s06crop.fit
 RSpec V1.3.0 (Build: 39) VegaA06012s06crop4orderData.dat and VegaA06012s06crop4orderData.ini
 RSpec V1.3.0 (Build: 39) VegaA06012s06cropCal5pointsE.ini
RSpec NonLinear 1st Order Calibration
 The first order calibration which is linear has the Hα, Hβ and Hγ looking good on the spectrum chart. Hδ, Hε and Hζ absorption lines are at the wrong wavelength.
RSpec NonLinear 2nd Order Calibration
 The second order calibration improves the Hδ, Hε, Hζ, Hα and A(O_{2}) absorption lines. Hβ and Hγ absorption lines are worse than first order.
RSpec NonLinear 3rd Order Calibration
 The third order calibration improves Hβ, Hα and A(O_{2}) absorption lines. But, Hγ and Hδ are worse than second order calibration.
RSpec NonLinear 4th Order Calibration
 The forth order calibration has slight improvements over the third order calibration. There is very little difference between third order and forth order calibration looking at the spectrum chart. The forth order has the lowest RMS values with 0.00 (RSpec) and 2.84 (Excel).
