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B. Imager Pixel-Scale and Slit Length


On 6 June 2007, I obtained spectra of five of the double stars from Table 5. I did not use the focal-reducing lens on this night. For each star I obtained spectra at both high- and low-dispersion, in order to test for possible dispersion dependence of the spatial scale. Figure 35 shows a high- and low-dispersion spectral image of one of the double star targets from this night. For each spectral image, I measured the separation in pixels in the spatial direction of the centroids of the two stars in bins of 50 pixels in the wavelength direction. I did this to test for any possible wavelength dependence of the spatial scale. Figure 36 shows an example of a plot from which the separation was measured.

  • Figure 35: Top: A low-dispersion spectral image of BD+84 290. Bottom: A high-dispersion spectral image of BD+84 290. Both spectra obtained on 06 June 2007.

  • Figure 36: A 50-pixel spatial slice of the spectral image from the top of Fig. 35.

    There is no evidence for any dispersion dependence of the spatial scale, based on my analysis of the data from 6 June 2007. Thus, on 20 July 2007, I obtained only low-dispersion spectra of five of the double stars from Table 5. On this night I used the focal reducing lens. As for the data from 6 June, for each spectral image, I measured the separation in pixels in the spatial direction of the centroids of the two stars in bins of 50 pixels in the wavelength direction. There is no evidence for any wavelength dependence of the spatial scale in either data set. The results of these tests on the spatial scale of the spectral images are given in Table 7.

    Table 7 - Pixel Scale and Slit Length for Main CCD
    Mode Scale Slit Length
    '' per pixel ''
    No lens 0.25 +/- 0.01 160
    Lens 0.34 +/- 0.01 215
    The slit length in pixels has currently only been determined for low-dispersion.


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    Updated: 2007 September 3 [pbe]