DAO Observations DAO Observations and and

InstrumentationInstrumentation

Jason GrunhutJason Grunhut

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

The 72’’ Dome and The 72’’ Dome and TelescopeTelescope

Available ResidencesAvailable Residences

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.

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.

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

Problem of Charge TrapsProblem of Charge Traps

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.

Results: 53 CamResults: 53 Cam

Normalized Spectra:Normalized Spectra:53 Cam53 Cam

Normalized Spectra:Normalized Spectra:HD215441HD215441

Field Measurement Field Measurement Comparisons: 53 CamComparisons: 53 Cam

Field MeasurementField MeasurementComparison: HD71866Comparison: HD71866

Field Measurement Field Measurement Comparison: Theta Aur Comparison: Theta Aur

Field Measurement Field Measurement Comparison: HD32633Comparison: HD32633

Field Measurement Field Measurement Comparison: HD10221Comparison: HD10221

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

THE END

Beautiful VictoriaBeautiful Victoria