NSI 2011 INDEX - New

Vega Low Resolution Spectrum
Image August 2, 2011 at 11:04 am PDT

Vega Spectrum


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 the horizontal line on the right side. The vertical stripes in the spectrum are absorption lines from the star and from the Earth's atmosphere.

The round spectral order zero has CCD blooming streaks at the bottom of the star image because the exposure was optimized for the spectrum intensity and the CCD camera bloomed on the high intensity zero order star. In other words, the star is over exposed but the spectrum exposure is fine.

The focus was optimized for Hα part of the spectrum in preparation for imaging a quasar KUV18217+6419 later in the evening. As a result, the short wavelength part of the spectrum (left side of the spectrum) is out of focus and is wider than the longer wavelengths (right side of the spectrum). The vertical absorption lines on the left side of the spectrum are the Hζ, Hε, Hδ, Hγ and Hβ absorption lines. The vertical absorption lines on the right side of the spectrum are the Hα absorption line and the telluric O2 and H2O absorption lines.

Vega Spectrum Calibrated for Instrument Response

Vega Spectrum Chart
  • The spectrum vertical axis is the intensity values of the spectrum image which have been calibrated for the instrument response.
  • The red marks are measured data points.
  • The spectrum horizontal axis is wavelength in angstroms (Å).
  • The yellow reference markers show hydrogen Balmer absorption lines (Hα, Hβ, Hγ, Hδ, Hε and Hζ) and Fraunhofer telluric O2 absorption bands/lines (a, B, A, Z and y) and H2O absorption band.
  • Below the spectrum chart is a synthesize color spectrum band generated from the spectrum data.

Vega Spectrum Compared to A0V Star in Pickels Synthetic Reference Library

Vega Spectrum Chart
  • The A0V reference synthetic spectrum (blue line) is from RSpec Pickels’ reference library.
  • The short wavelength absorption lines are weak because this part of the spectrum is not in sharp focus. The focus was optimize for the longer wavelengths.
  • The shape of the continuum shows that the temperature of Vega peaks in the UV part of the spectrum.
    • NAAP Blackbody Curves demonstration.
      • Set the blackbody curve to Vega's temperature which is 9602 ± 180 K.
      • Compare the above Vega spectrum with the blackbody curve at 9610 K. The blackbody curve peak is at 3015 Å which is in the UV part of the electromagnetic spectrum.
      • Vega's spectrum continuum shape shows us its blackbody temperature.
      • Vega spectrum drops on the left side because of the Balmer continuum (Balmer jump) . Therefore, Vega's spectrum does not follow a blackbody curve at the shorter wavelengths.
NAAP Blackbody Curves demonstration

Vega Spectrum (uncalibrated intensity data)

Vega Spectrum Chart
  • This Vega spectrum shows the calibration of the horziontal axis in angstroms.
  • The vertical axis is the spectrum intensity that has not been calibrated for the instrument response curve. See instrument response curve below at the bottom of this web page.

Vega Spectrum (uncalibrated intensity data) with the Continuum Removed

Vega Spectrum Chart
  • The above spectrum profile is the Vega spectrum (uncalibrated intensity data) that has been divided by the shape of its own continuum to remove the continuum.
  • Notice how much more easly it is to see the Fraunhofer telluric O2 absorption bands/lines (a, B, A, Z and y)
  • The wavelength calibration for the Fraunhofer a and B absorption banda and Hα absorption line are too short of wavelength on the spectrum.
  • The difference between CCD camera pixels at Hα is approximately 17.9 Å.

Imaging Processing

  • Diffraction Limited MaxIm DL V5.07.
    • Crop star and spectrum.
    • Save as FIT for RSpec and JPG for web site.

RSpec Non-Linear Calibration Wizard

Spectrum Calibration with RSpec

Instrument Response Profile

Instrument Response Profile

Vega Spectrum Data

  • RSpec V1.3.0 (Build: 39) data in VegaA06-012s06crop4orderDataA.zip
    • VegaA06-012s06crop.fit
    • VegaA06-012s06crop4orderData.dat
    • VegaA06-012s06crop4orderData.ini
    • VegaA06-012s06cropCal5pointsE.ini
    • QSIRAWInstResponseSmooth7.dat

Observing Information

Imaging Equipment

Vega Spectrum Links

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.