Star Vega Spectrum



In the above image star Vega round spectral order zero is in the upper left corner and it's first order blazed grating spectrum is located on the top to the right side. The processed spectrum band is below the blazed grating spectrum.

  • Star Vega spectral type is A0V and its luminosity class is a V.
  • Spectrum is dominated by hydrogen H-alpha , H-beta and H-gamma absorption lines.
  • This one of four images used to calibrate the equipment spectrum measurements for August 6, 2010.
  • Spectrum image was taken with a 150mm (6 inches) telescope and a Rainbow Optics diffraction grating filter.
  • Image: vega08062010-01405s.fit
  • The spectrum image was analyzed by ImageJ (Image Processing and Analysis in Java).

Spectroscopy Team

The spectrum image was taken by the below spectroscopy team:

Spectrum Selection

spectrum Selection

  • The above cropped image shows the rectangle selection area that was used for the spectrum 3-D surface plot, the spectrum band and the spectrum chart below.
  • The selection area is 6 rows by 363 columns.
  • The short spectrum wavelengths are on the left in the selection area.
  • The long spectrum wavelengths are on the right in the selection area.
  • The black pixel in the zero mode is the centroid location that is used as the reference for the spectrum wavelength calibration.

Spectrum 3-D Surface Plot

Spectrum Surface Plot

  • This is a spectrum 3-D surface plot of the selection area.
  • The short wavelengths are on the left and the long wavelengths are on the right.
  • The average of the rows is used to generate the spectrum band and the spectrum chart below.

Spectrum Band

  • The average of the vertical column of pixels in the selection area is used to generate the spectrum band below.
  • The spectrum band is three times the original horizontal size so that it closely matches the below spectrum chart width.
  • Short wavelengths are on the left and long wavelengths are on the right.
  • The spectrum band is linearly scaled between the intensity 20 to 230 to better see the spectrum details. (Black = 0 and white = 255)
  • No sharpening or other image processing was done on the spectrum band.

Spectrum Chart

Spectrum Chart

  • The above chart is the average of the vertical pixels in the selection area of the spectrum.
  • The vertical axis is the intensity values (average of the vertical pixels in the selection) of the spectrum image.
  • Four reference yellow line markers were added.

Spectrum Calibration

  • Vega H-alpha absorption line was used to calibrate the x axis in angstroms by measuring the distance of the grating to CCD.
    • Vega H-alpha absorption line distance was measured from the centroid of the spectral order zero.
    • The below table shows the four images used and the calculated grating distance between the grating and the CCD.
    • The grating distance mean is 18.3272 mm with a standard deviation of 0.01414 mm.
    Vega Spectrum Calibration Table
  • The first angstrom calibration equation is =SIN (ATAN (0.0000068* pixel distance /.01832719265135))*0.000005*10000000000
    • is light wavelength measured in angstroms.
    • 0.0000068 m is QSI532ws pixel size (6.8 microns).
    • Pixel distance is the horizontal pixel distance from the centroid of spectral order zero.
    • .01832719265135 is the distance of the grating to CCD (18.3272 mm).
    • 0.000005 m is the distance between the Rainbow Optics grating filter lines (200 lines/mm grating).
    • 10000000000 converts the wavelength from meters to angstroms.
  • The second calibration uses H-delta, H-gamma, H-beta and H-alpha absorption lines to fine adjust the angstroms scale.

Signal to Noise Ratio

Background Measurement Selection

The background measurements are of the above yellow selection box.


Monitor Test Pattern

The following test pattern is to help you adjust your monitor to best view the CCD astro images. The test pattern is used for adjusting monitor brightness, and contrast. Adjust monitor brightness and contrast to see all 16 gray scale levels. The most important adjustment when viewing astro images is to see the differences in all of the black bands.