Sky Background Measurements at Los Leones C B
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 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
Instrumentation • • • Two PMT’s XP 2012 + Head Electronics High resolution volmeter HP 34401 + GPIB bus Lab View software driver + DAQ on laptop Telescope with 15 cm diam. mirror - f/8 MUG 2 and Hi. Res UV Filters Measurements done at : • Buenos Aires (Top of Tandar Lab building) • San Rafael (Observatory of Natural Science Museum) • Auger site, at Los Leones
Targets • A star (Alfa Centauro)and its nearby background in three different places: Bs. As, SR, Los Leones • Background, looking NO at Los Leones • Zenit with the telescope and with an open PMT.
Scaling our measurements to actual FD size Auger: • FD mirror area - camera area = 3 m 2 • Aperture 2. 25 deg 2 Telescope: • Mirror area = 1. 77 10 -2 m 2 • Aperture 2. 34 deg 2 Scaling factor: 163
Scaling the directly exposed PMT+HE 103 deg • Photocathode area : 8. 10 - 4 m 2 • Scaling Factor : 3 m 2 x 5. 38 10 -4 str / 8 10 -4 m 2 / 2. 37 sr SF= FD/PMT = 0. 85
Square wave on LED illuminating the 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. FILTER WHEEL PMT 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
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.
Pino Torinese no filter Relative mag. = -2. 5 log(i/i 0) i 0: PMT current from Vega Star spectra: blue (B) white (A) orange (K) red (M) Note that the departure from the straight line is due to the higher weight of the background for fainter stars.
Pino Torinese U filter Star spectra: blue (B) white (A) Orange and red stars give too low signals to be measured
Preparing Telescope, PMT and Filter adapters, etc. . .
Alfa Centauro - MUG 2 Filter - Los Leones Telescope Measurement Star ( 0. 253 phel/100 ns = 405 f. A) Background (0. 044 phel/100 ns = 70 f. A)
Alfa Centauro - MUG 2 Filter - Los Leones Signal scaled to Auger Dark level Background Star
Alfa Centauro - Hi. Res Filter - Los Leones Background (0. 039 phel/100 ns = 62 f. A) Star (0. 252 phel/100 ns = 403 f. A)
Zenit - MUG 2 Filter - Los Leones PMT directly exposed Background (10 phel/100 ns) Auger scaled: 8. 5 phel/100 ns No Filter
MUG 2 Filter - Alfa Centauro and Background Different places
- Slides: 21