Illusion - A Fabry-Perot Data-Cube
Synthesizer
Quint, B.C.[1]; Taylor, K.[1]; Muramatsu, M.[1]; Ferrari, F.[2]; Mendes deOliveira, C.[1]ABSTRACT
Illusion is a software package designed to synthesize Fabry­Perot data for the Brazilian Tunable Imager Filter (BTFI) project which isdeveloping an instrument for the SOAR telescope at the Universidade de São Paulo in collaboration with several other institutes in Brazil,
Canada and France. The Illusion package synthesizes data to help in the development of data­reduction routines, to train observers and tosimulate observations in different contexts. The synthesized data are obtained using different kinds of sources located in the telescope's
image plane modified by the Fabry­Perot Airy profile. The results are delivered as data­cubes in the FITS format and they have been apowerful resource in the development of new data­reduction routines and for the training of the BTFI's software and observing groups.

4. SYNTHESIZED DATA

1. INTRODUCTION
Illusion is a package developed in the Python language to simulate
Fabry-Perot data in the context of the BTFI instrument for SOAR.
This project requires the understanding of the interferometry
underlying a Fabry-Perot as used as a tunable optical filter.

The synthesized data shown below shows the results
generated by a Fabry-Perot illuminated by a spatially uniform,
550nm monochromatic source at a spectral resolution of
20,000 and with a finesse of 25. The camera's focal length is
350 mm imaging onto a detector having pixels of 16 um.

The synthetic data are recorded as a data-cube, with x,y spatial andz spectral dimensions. They are used to help in the development of a
new library of programs to calibrate and reduce the real data,obtained with the instrument.

Monochromatic Flat: the source is a monochromatic even
Illuminated screen located at infinity. These images have 1600x1600
pixels.

Illusion simulates data by considering four different kinds of sources(Monochromatic Flat, Monochromatic Image, Multi-spectral Flat andMulti-spectral Image) to aid in different levels and requirements of thesimulations.

2. OPTICAL ARRANGEMENT
Currently Illusion uses a classical arrangement for a Fabry­Perot,
mounted at the pupil plane within the collimated section, such thatinterference fringes are formed
Fabry-Perot
Telescopeon the detector con­focal with
the image of the sky.
Fig. 1 shows the arrangementthat Illusion uses to do thesimulations.

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Multi­wavelength Flat: the source is spatially uniform but has three
wavelengths of zero width. Here, the blue rings are at 470nm, thegreen ones are at 550nm and the red ones are at 620nm. As
before, each frame has 1600x1600 pixels.

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Collimator

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CameraMonochromatic Sky Image: the source ismodeled as a monochromatic image located atinfinity. In this case, it is represented by the M74
galaxy at 539.7nm imaged by the same Fabry­
Perot. Here, each frame has 560x560 pixels.

Figure 1 – Optical Arrangement

The ellipses in blue represent the optical system lenses (telescope,collimator and camera). The rectangles in orange represent theetalon plates.

3. DATA-CUBE STRUCTURE
The data­cube is stored as a FITS file containing a stack of tunablefilter images centered at different wavelengths generally sampled at
the Nyquist limit. The X and Y direction in a cube define the spatial
information for a given wavelength while the Z direction gives thespectral information for each pixel.

Figure 2 – Data-Cube Structure

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Multiwalvelength image: the simulated source is aset of images where each frame is taken at adifferent wavelength. The RGB images below show
M74 in three different wavelengths: 642.5nm (R),539.7nm (G) and 433.1nm (B). Again, the frames
have 560x560 pixels.

RGB composition
before Illusion.

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Acknowledgments

References* Born, Max, and Wolf, Emil: Principle of Optics, Cambridge University Press, 1999
* Lutz, Mark: Programmin Python, O´Reilly Media, Eds: O´Brien, Mary, 2006
* Barrett, P. E. & Bridgman, W. T. 1999, in ASP Conf. Ser., Vol. 172, ADASS VIII,eds. D. M. Mehringer, R. L. Plante, & D. A. Roberts (San Francisco: ASP), 483

Original Image* http://matplotlib.sourceforge.net/* http://numpy.scipy.org/[1] Universidade de São Paulo (USP) – Brazil[2] Universidade Federal do Pampa (Unipampa) – Brazil

This work is part of the Master's thesis of Bruno Quint and it is supported by
CPNQ scholarship (process n.136015/2008­5).

bquint@astro.iag.usp.br
http://www.astro.iag.usp.br/~bquint