scholarly journals Commissioning Results of a New Polarimeter: Denver University Small Telescope Polarimeter (DUSTPol)

2014 ◽  
Vol 10 (S305) ◽  
pp. 200-206
Author(s):  
T. M. Wolfe ◽  
R. Stencel ◽  
G. Cole
Keyword(s):  
Data Reduction ◽  
Interaction Parameters ◽  
Small Telescope ◽  
Dual Beam ◽  
Instrumental Polarization ◽  
Active Stars ◽  
Optical Wavelengths

AbstractDUSTPol is a dual-beam polarimeter that operates in optical wavelengths, and was built to promote the study of linear polarimetry with smaller telescopes. DUSTPol's performance has demonstrated low instrumental polarization at 0.05 ± 0.02%. This poster presents commissioning results as well as early science observations, and describes software used for data reduction. Recent polarimetric results of RS CVn systems and Wolf-Rayet stars, discussed herein, indicate shape and interaction parameters. By promoting the development of similar polarimeters at other institutions, DUSTPol will serve to establish new collaborative surveys of cool active stars, as well as systems showing evidence of containing complex stellar environments.

scholarly journals Characterization of a dual-beam, dual-camera optical imaging polarimeter

2020 ◽  
Vol 494 (4) ◽  
pp. 4676-4686
Author(s):  
Manisha Shrestha ◽  
Iain A Steele ◽  
Andrzej S Piascik ◽  
Helen Jermak ◽  
Robert J Smith ◽  
...  
Keyword(s):  
Optical Imaging ◽  
Data Reduction ◽  
High Sensitivity ◽  
Cmos Technology ◽  
Low Noise ◽  
Reduction Algorithm ◽  
Dual Beam ◽  
Instrumental Polarization ◽  
Transient Sources

ABSTRACT Polarization plays an important role in various time-domain astrophysics to understand the magnetic fields, geometry, and environments of spatially unresolved variable sources. In this paper we present the results of laboratory and on-sky testing of a novel dual-beam, dual-camera optical imaging polarimeter (MOPTOP) exploiting high sensitivity, low-noise CMOS technology, and designed to monitor variable and transient sources with low systematic errors and high sensitivity. We present a data reduction algorithm that corrects for sensitivity variations between the cameras on a source-by-source basis. Using our data reduction algorithm, we show that our dual-beam, dual-camera technique delivers the benefits of low and stable instrumental polarization (<0.05 per cent for lab data and <0.25 per cent for on sky data) and high throughput while avoiding the additional sky brightness and image overlap problems associated with dual-beam, single-camera polarimeters.

scholarly journals Tips and tricks in linear imaging polarimetry of extended sources with FORS2 at the VLT

2020 ◽  
Vol 634 ◽  
pp. A70
Author(s):  
S. González-Gaitán ◽  
A. M. Mourão ◽  
F. Patat ◽  
J. P. Anderson ◽  
A. Cikota ◽  
...  
Keyword(s):  
Optical System ◽  
Signal To Noise Ratio ◽  
Broad Band ◽  
Good Control ◽  
High Signal ◽  
Tips And Tricks ◽  
Dual Beam ◽  
Instrumental Polarization ◽  
Imaging Polarimetry ◽  
Extended Sources

Context. Polarimetry is a very powerful tool for uncovering various properties of astronomical objects that otherwise remain hidden in standard imaging or spectroscopic observations. While common observations only measure the intensity of light, polarimetric measurements allow us to distinguish and measure the two perpendicular components of the electric field associated with the incoming light. By using polarimetry it is possible to unveil asymmetries in supernova explosions, properties of intervening dust, characteristics of atmosphere of planets, among others. However, the reliable measurement of the low polarization signal from astronomical sources requires a good control of spurious instrumental polarization induced by the various components of the optical system and the detector. Aims. We perform a detailed multi-wavelength calibration study of the FORS2 instrument at the VLT operating in imaging polarimetric mode to characterize the spatial instrumental polarization that may affect the study of extended sources. Methods. We used imaging polarimetry of high signal-to-noise ratio blank field BVRI observations during the full moon, when the polarization is expected to be constant across the field of view and deviations originate from the instrument, and a crowded star cluster in broad-band RI and narrow-band Hα filters, where the individual polarization values of each star across the field can be measured. Results. We find an instrumental polarization pattern that increases radially outwards from the optical axis of the instrument reaching up to 1.4% at the edges, depending on the filter. Our results are closely approximated by an elliptical paraboloid down to less than ∼0.05% accuracy, and ∼0.02% when using non-analytic fits. We present 2D maps to correct for this spurious instrumental polarization. We also give several tips and tricks for analyzing polarimetric measurements of extended sources. Conclusions. FORS2 is a powerful instrument that allows the linear polarimetry of extended sources to be mapped. We present and discuss a methodology that can be used to measure the polarization of such sources, and to correct for the spatial polarization induced in the optical system. This methodology could be applied to polarimetric measurements using other dual-beam polarimeters.

scholarly journals Polarimetric imaging mode of VLT/SPHERE/IRDIS

2020 ◽  
Vol 633 ◽  
pp. A64 ◽  
Author(s):  
R. G. van Holstein ◽  
J. H. Girard ◽  
J. de Boer ◽  
F. Snik ◽  
J. Milli ◽  
...  
Keyword(s):  
Linear Polarization ◽  
Data Reduction ◽  
Near Infrared ◽  
Circumstellar Disks ◽  
Correction Method ◽  
Polarization Effects ◽  
Very Large Telescope ◽  
Instrumental Polarization ◽  
Imaging Polarimetry ◽  
Data Reduction Method

Context. Circumstellar disks and self-luminous giant exoplanets or companion brown dwarfs can be characterized through direct-imaging polarimetry at near-infrared wavelengths. SPHERE/IRDIS at the Very Large Telescope has the capabilities to perform such measurements, but uncalibrated instrumental polarization effects limit the attainable polarimetric accuracy. Aims. We aim to characterize and correct the instrumental polarization effects of the complete optical system, that is, the telescope and SPHERE/IRDIS. Methods. We created a detailed Mueller matrix model in the broadband filters Y, J, H, and Ks and calibrated the model using measurements with SPHERE’s internal light source and observations of two unpolarized stars. We developed a data-reduction method that uses the model to correct for the instrumental polarization effects, and applied it to observations of the circumstellar disk of T Cha. Results. The instrumental polarization is almost exclusively produced by the telescope and SPHERE’s first mirror and varies with telescope altitude angle. The crosstalk primarily originates from the image derotator (K-mirror). At some orientations, the derotator causes severe loss of signal (> 90% loss in the H- and Ks-band) and strongly offsets the angle of linear polarization. With our correction method we reach, in all filters, a total polarimetric accuracy of ≲0.1% in the degree of linear polarization and an accuracy of a few degrees in angle of linear polarization. Conclusions. The correction method enables us to accurately measure the polarized intensity and angle of linear polarization of circumstellar disks, and is a vital tool for detecting spatially unresolved (inner) disks and measuring the polarization of substellar companions. We have incorporated the correction method in a highly-automated end-to-end data-reduction pipeline called IRDAP, which we made publicly available online.

scholarly journals Testing and data reduction of the Chinese Small Telescope Array (CSTAR) for Dome A, Antarctica

2010 ◽  
Vol 10 (3) ◽  
pp. 279-290 ◽  
Author(s):  
Xu Zhou ◽  
Zhen-Yu Wu ◽  
Zhao-Ji Jiang ◽  
Xiang-Qun Cui ◽  
Long-Long Feng ◽  
...  
Keyword(s):  
Data Reduction ◽  
Dome A ◽  
Telescope Array ◽  
Small Telescope

scholarly journals Polarimetric imaging mode of VLT/SPHERE/IRDIS

2020 ◽  
Vol 633 ◽  
pp. A63 ◽  
Author(s):  
J. de Boer ◽  
M. Langlois ◽  
R. G. van Holstein ◽  
J. H. Girard ◽  
D. Mouillet ◽  
...  
Keyword(s):  
Linear Polarization ◽  
Data Reduction ◽  
Correction Method ◽  
High Contrast ◽  
Polarization Effects ◽  
Instrumental Polarization ◽  
Polarimetric Imaging ◽  
Imaging Mode ◽  
Instrument Configuration

Context. Polarimetric imaging is one of the most effective techniques for high-contrast imaging and for the characterization of protoplanetary disks, and it has the potential of becoming instrumental in the characterization of exoplanets. The Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument installed on the Very Large Telescope (VLT) contains the InfraRed Dual-band Imager and Spectrograph (IRDIS) with a dual-beam polarimetric imaging (DPI) mode, which offers the capability of obtaining linear polarization images at high contrast and resolution. Aims. We aim to provide an overview of the polarimetric imaging mode of VLT/SPHERE/IRDIS and study its optical design to improve observing strategies and data reduction. Methods. For H-band observations of TW Hydrae, we compared two data reduction methods that correct for instrumental polarization effects in different ways: a minimization of the “noise” image (Uϕ), and a correction method based on a polarimetric model that we have developed, as presented in Paper II of this study. Results. We use observations of TW Hydrae to illustrate the data reduction. In the images of the protoplanetary disk around this star, we detect variability in the polarized intensity and angle of linear polarization that depend on the pointing-dependent instrument configuration. We explain these variations as instrumental polarization effects and correct for these effects using our model-based correction method. Conclusions. The polarimetric imaging mode of IRDIS has proven to be a very successful and productive high-contrast polarimetric imaging system. However, the instrument performance is strongly dependent on the specific instrument configuration. We suggest adjustments to future observing strategies to optimize polarimetric efficiency in field-tracking mode by avoiding unfavorable derotator angles. We recommend reducing on-sky data with the pipeline called IRDAP, which includes the model-based correction method (described in Paper II) to optimally account for the remaining telescope and instrumental polarization effects and to retrieve the true polarization state of the incident light.

The CLASSIC/CLIMB Data Reduction: The Math

2014 ◽  
Vol 69-70 ◽  
pp. 75-99
Author(s):  
T. ten Brummelaar
Keyword(s):  
Data Reduction

ELECTRONIC AREA DETECTOR DATA REDUCTION SYSTEM AT THE SRS

1986 ◽  
Vol 47 (C5) ◽  
pp. C5-109-C5-113
Author(s):  
J. W. CAMPBELL ◽  
D. CROFT ◽  
J. R. HELLIWELL ◽  
P. MACHIN ◽  
M. Z. PAPIZ ◽  
...  
Keyword(s):  
Data Reduction ◽  
Area Detector ◽  
Reduction System

INOVASI PEMBELAJARAN AKIDAH AKHLAK MENGGUNAKAN METODE ROLE PLAY DALAM MENINGKATKAN PRESTASI BELAJAR SISWA

2018 ◽  
Vol 2 (1) ◽  
pp. 52-63
Author(s):  
Ansori Ansori
Keyword(s):  
Data Reduction ◽  
Role Play ◽  
Learning Goals ◽  
New Paradigm ◽  
Learning Materials ◽  
Analysis Technique ◽  
Flexible Schedule ◽  
Using Data ◽  
Real Action

The use of various methods will greatly help students in achieving learning goals. As role play method is one way mastery of learning materials through the development of imagination and appreciation of students on learning materials. Data collection techniques in this study are observation, interviews, and documentation. To analyze the data in this research using data analysis technique of Miles and Huberman model that is data reduction (Data Reduction), data presentation (Data Display) and conclusion (Conclution Drawing / verification) The findings in this research is innovation of role play method can change paradigm to the new paradigm so that the role of the teacher is more as a facilitator, counselor, consultant, and comrade study Flexible schedule, open as needed Learning directed by students themselves Problem-based, project, real world, real action, and reflection Design and investigation. Computers as tools, and dynamic media presentations.

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