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DAO Observations and Instrumentation

DAO Observations and Instrumentation. Jason Grunhut. Introduction to the Dominion astrophysical Observatory. Situated on the peak of Observatory Hill in Victoria on Vancouver Island, British Columbia. 19 th mag dark skies Two telescopes available 1.85 m Plaskett f/18 Cassegrain focus

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DAO Observations and Instrumentation

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  1. DAO Observations and Instrumentation Jason Grunhut

  2. Introduction to theDominion astrophysical Observatory • Situated on the peak of Observatory Hill in Victoria on Vancouver Island, British Columbia. • 19th mag dark skies • Two telescopes available • 1.85 m Plaskett • f/18 Cassegrain focus • f/5 modified Newtonian focus • Primarily used for spectroscopy • fully automatic pointing and guiding • 1.22 m McKeller telescope • Primarily used with Coudé focus. • Used for both spectroscopy and photometry

  3. The 72’’ Dome and Telescope

  4. Available Residences

  5. The Polarimeter • designed and built by Dmitry Monin • made from commercially available products • cheap • installed immediately after spectrograph slit. • achromatic quarter-wave plate converts light into two orthogonal linear polarizations (vertical/horizontal). • Ferroelectric Liquid Crystal (FLC) acts as half-wave plate • voltage controlled • near instantaneous change (few ns). • Calcite beam-displacer use to form image on CCD.

  6. The Polarimeter - Continued • Take many spectra in two orthogonal states to remove instrumental effects. • Best at several Hz level • Usually use about 50-60 shifts. • Record both orthogonal states simultaneously.

  7. CCD Image • Cover 4750-5000 Å • 0.15 Å/pixel dispersion • Resolving power of ~10 000 • ~70 G accuracy for 6th magnitude star in about 20 minutes (emission line star) using Fourier cross-correlation

  8. Problem of Charge Traps

  9. Reductions • Reduced and extracted using IRAF • Correct for bias and bad pixels • Each beam is extracted separately • Matching beams are then combined • Single wavelength calibration is then applied • Stokes V is simply calculated from the difference of the two spectra (no prior normalization) • Resulting Stokes V and I spectra are normalized.

  10. Results: 53 Cam

  11. Normalized Spectra:53 Cam

  12. Normalized Spectra:HD215441

  13. Field Measurement Comparisons: 53 Cam

  14. Field MeasurementComparison: HD71866

  15. Field Measurement Comparison: Theta Aur

  16. Field Measurement Comparison: HD32633

  17. Field Measurement Comparison: HD10221

  18. Issues and Future • Spurious detections in null-field standard stars. • Procyon, Theta Cep, Sigma And • Likely due to poor guiding in Declination. • Possibly due to poor alignment of crystal. • Improved since first tests. • Regression routine not entirely suitable as lines are well resolved. • Use Fourier Cross-Correlation • Use LSD method

  19. THE END

  20. Beautiful Victoria

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