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Sky Background Measurements at Los Leones

Sky Background Measurements at Los Leones. C.B.Bonifazi 1,3 , D.V.Camin 6 , P.F.Gomez Vitale 4 , V.Grassi 6 , M.Lantz 3 , M.Lapolla 6 , M. Santander 2,5 , M.Santarrosa 2,5 , A.Risi 2,5 , D.Rodriguez 3 , V.Scherini 6 , G.Sequeiros 5 1-Laboratorio Tandar, CNEA

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Sky Background Measurements at Los Leones

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  1. Sky Background Measurements at Los Leones C.B.Bonifazi1,3, D.V.Camin 6, P.F.Gomez Vitale 4, V.Grassi6, M.Lantz 3, M.Lapolla 6, M. Santander 2,5, M.Santarrosa 2,5, A.Risi 2,5, D.Rodriguez 3, V.Scherini6, G.Sequeiros 5 1-Laboratorio Tandar, CNEA 2-Museo de Ciencias Naturales de San Rafael 3-Universidad Nacional de Buenos Aires 4-Universidad Tecnologica de Mendoza 5-Universidad Tecnologica de San Rafael 6-Universita’ di Milano/INFN

  2. Instrumentation • Two PMT’s XP2012 + Head Electronics • High resolution volmeter HP34401 + GPIB bus • Lab View software driver + DAQ on laptop • Telescope with 15 cm diam. mirror - f/8 • MUG2 and HiRes UV Filters Measurements done at : • Buenos Aires (Top of Tandar Lab building) • San Rafael (Observatory of Natural Science Museum) • Auger site, at Los Leones

  3. Targets • A star (Alfa Centauro)and its nearby background in three different places: BsAs, SR, Los Leones • Background, looking NO at Los Leones • Zenit with the telescope and with an open PMT.

  4. Scaling our measurements to actual FD size Auger: • FD mirror area - camera area = 3 m2 • Aperture 2.25 deg2 Telescope: • Mirror area = 1.77 10-2 m2 • Aperture 2.34 deg2 Scaling factor:163

  5. Photocathode area : 8.10- 4m2 Scaling Factor : 3m2 x5.38 10-4str / 8 10-4 m2 / 2.37sr SF= FD/PMT = 0.85 Scaling the directly exposed PMT 103 deg PMT+HE

  6. Square wave on LED illuminating the PMT

  7. Telescope data: primary mirror diameter 1050 mm focal lenght 9943 mm image scale 20.7 arcsec./mm linear obstruction 60% http://www.to.astro.it/Services/services.html FILTER WHEEL PMT Preliminary measurements at Torino Astronomical Observatory The following measurements were taken at Pino Torinese Astronomical Observatory using the 1.05 m REOSC telescope. The two graphs show the different response of the PMT to orange, white and blue stars.

  8. The UV filter was provided by the observatory in the filter wheel, it is a U band filter from the UBVRI system made of 3 filters superimposed. The spectral response is given below.

  9. Star spectra: blue (B) white (A) orange (K) red (M) Pino Torinese no filter Relative mag.= -2.5log(i/i0) i0: PMT current from Vega Note that the departure from the straight line is due to the higher weight of the background for fainter stars.

  10. Star spectra: blue (B) white (A) Pino Torinese U filter Orange and red stars give too low signals to be measured

  11. Preparing Telescope, PMT and Filter adapters, etc...

  12. Alfa Centauro - MUG2 Filter - Los LeonesTelescope Measurement Star ( 0.253 phel/100ns = 405 fA) Background (0.044 phel/100ns = 70 fA)

  13. Alfa Centauro - MUG2 Filter - Los LeonesSignal scaled to Auger Dark level Background Star

  14. Alfa Centauro - HiRes Filter - Los Leones Background (0.039 phel/100ns = 62 fA) Star (0.252 phel/100ns = 403 fA)

  15. Zenit - MUG2 Filter - Los LeonesPMT directly exposed Background (10 phel/100ns) Auger scaled: 8.5 phel/100ns No Filter

  16. MUG2 Filter - Alfa Centauro and Background Different places

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