DAO Observations and Instrumentation
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DAO Observations DAO Observations and and
InstrumentationInstrumentation
Jason GrunhutJason Grunhut
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Introduction to theIntroduction to theDominion astrophysical Dominion astrophysical
ObservatoryObservatory Situated on the peak of Observatory Hill in Victoria on Situated on the peak of Observatory Hill in Victoria on
Vancouver Island, British Columbia.Vancouver Island, British Columbia. 1919thth mag dark skies mag dark skies Two telescopes availableTwo telescopes available
1.85 m Plaskett 1.85 m Plaskett f/18 Cassegrain focusf/18 Cassegrain focus f/5 modified Newtonian focusf/5 modified Newtonian focus Primarily used for spectroscopyPrimarily used for spectroscopy fully automatic pointing and guidingfully automatic pointing and guiding
1.22 m McKeller telescope1.22 m McKeller telescope Primarily used with CoudPrimarily used with Coudé focus.é focus. Used for both spectroscopy and photometryUsed for both spectroscopy and photometry
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The 72’’ Dome and The 72’’ Dome and TelescopeTelescope
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Available ResidencesAvailable Residences
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The PolarimeterThe 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.
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The Polarimeter - ContinuedThe Polarimeter - Continued
Take many spectra Take many spectra in two orthogonal in two orthogonal states to remove states to remove instrumental effects.instrumental effects. Best at several Hz Best at several Hz
levellevel Usually use about Usually use about
50-60 shifts.50-60 shifts. Record both Record both
orthogonal states orthogonal states simultaneously.simultaneously.
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CCD ImageCCD 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
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Problem of Charge TrapsProblem of Charge Traps
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ReductionsReductions
Reduced and extracted using IRAFReduced and extracted using IRAF Correct for bias and bad pixelsCorrect for bias and bad pixels Each beam is extracted separately Each beam is extracted separately
Matching beams are then combinedMatching beams are then combined Single wavelength calibration is then appliedSingle wavelength calibration is then applied Stokes V is simply calculated from the difference Stokes V is simply calculated from the difference
of the two spectra (no prior normalization)of the two spectra (no prior normalization) Resulting Stokes V and I spectra are normalized.Resulting Stokes V and I spectra are normalized.
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Results: 53 CamResults: 53 Cam
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Normalized Spectra:Normalized Spectra:53 Cam53 Cam
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Normalized Spectra:Normalized Spectra:HD215441HD215441
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Field Measurement Field Measurement Comparisons: 53 CamComparisons: 53 Cam
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Field MeasurementField MeasurementComparison: HD71866Comparison: HD71866
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Field Measurement Field Measurement Comparison: Theta Aur Comparison: Theta Aur
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Field Measurement Field Measurement Comparison: HD32633Comparison: HD32633
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Field Measurement Field Measurement Comparison: HD10221Comparison: HD10221
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Issues and FutureIssues and Future Spurious detections in null-field Spurious detections in null-field
standard stars.standard stars. Procyon, Theta Cep, Sigma AndProcyon, Theta Cep, Sigma And Likely due to poor guiding in Declination.Likely due to poor guiding in Declination. Possibly due to poor alignment of crystal.Possibly due to poor alignment of crystal.
Improved since first tests.Improved since first tests. Regression routine not entirely Regression routine not entirely
suitable as lines are well resolved.suitable as lines are well resolved. Use Fourier Cross-CorrelationUse Fourier Cross-Correlation Use LSD method Use LSD method
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THE END
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Beautiful VictoriaBeautiful Victoria