Transcript BaBar Pascos 2003

High Altitude UBV Observations
E.Giraud, I.Toledo, P.Valvin & G.Vasileiadis
LPTA/Montpellier, Un.Cath Chile
G.Vasileiadis, CTA Meeting 4-5 May-2006
Outline
•Physics Motivation
•The Instrument
•The Method
•La Silla/Alma Datasets
•In retrospective
G.Vasileiadis, CTA Meeting 4-5 May-2006
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Physics Motivation
• Measure Night Sky Parameters relevant to Cherenkov Telescopes
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Extinction Parameter
Night Sky Background
• Photometry of Night Sky at High Altitude (4-5Km)
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Thinner Atmosphere
Clearer skies
LaSilla/Hawaiian reference measurements (4300m)
• U,B and V measurements
Whats the gain for going higher ?!
G.Vasileiadis, CTA Meeting 4-5 May-2006
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The Instrument / Telescope
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Custom Newtonian 10”
Optical Guidance Systems
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F/4
UV custom coated mirrors
Takahashi EMT-200 mount
CCD ST7-XME SBIG
FOV 22x15arcmin
1.7arcsec/pixel (9mm)
Johnson UBV filter set.
Transportable (45kilos)
G.Vasileiadis, CTA Meeting 4-5 May-2006
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The Method / Photometry
 Photometry
 Using known Luminosity stars as reference
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Landolt Photometric Star Fields used
Standard Johnson U, B, V Filters Choice
Calibrate on a well-known site (La Silla )
Measure the extinction as a function of azimuth angle during
photometric nights, mainly in U
 Measure the sky background, mainly in U, directly on standard
fields
G.Vasileiadis, CTA Meeting 4-5 May-2006
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La Silla Datasets
La Silla Site at 2400m.
Camped outside EROS-II
Telescope.
Extinction Dataset using a standard
star.
 Luminosity measurements using U
V and B filters. ( 8 nights)
 Dataset using two distinctive
Landault star fields for Color
equations and Sky Background.
All Data used as “Calibration”
Comparison with known measurements
G.Vasileiadis, CTA Meeting 4-5 May-2006
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ALMA Site
Whatever follows done with the ALMA
Logistics Support.
Medical Support
All Night Radio Connection
Escorted to and from Site area
Jacques Lasalle (Site Security Manager)
G.Vasileiadis, CTA Meeting 4-5 May-2006
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The ALMA Site / APEX (5062m)
a
Source
G.Vasileiadis, CTA Meeting 4-5 May-2006
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The Alma Site 4000m and 5000m
•Two periods Nov 2005 and April 2006
•4 nighs at 4000m
•4 nights at 5000m
• -8 degrees temperatures
•Almost safe conditions
•All battery Operated
•UBV using std Landolt Star fields
•Direct comparison with La Silla
G.Vasileiadis, CTA Meeting 4-5 May-2006
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The data
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Standard stars used as reference
G.Vasileiadis, CTA Meeting 4-5 May-2006
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The data
Preliminary analysis shows
~0.1mag/airmass increase in
detected light between 2400 and
4000 m
(slope of Bouguer Curve)
Slopes : 0.43 and 0.33
mag/airmass
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Extinction Parameter Calculation for LaSilla and Alma
G.Vasileiadis, CTA Meeting 4-5 May-2006
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The data
Preliminary analysis shows a net benefit
in detected light between 2450m and
5000m for any air mass (close to a
magnitude for high airmass)
Transparency figure
LaSilla : 0.43 mag/airmass
Alma4K : 0.33
Alma5K : 0.26
G.Vasileiadis, CTA Meeting 4-5 May-2006
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In Perspective
• Succeed on having good data on La Silla and
some nights at 4000m and 5000m (ALMA
site)
• Promising Results
• Net Gain on Extinction Parameters for the U
• NSB comes in the near future
– Already we see the limit of our CCD ( square
star pattern)
• Keep Contact with ESO-ELT and Univ.Catholica Santiago/Chile.
G.Vasileiadis, CTA Meeting 4-5 May-2006
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