SDSS griz photometry (first experiences at Baja Observatory) T. Hegedüs – A. Szing – J. Vinkó* Baja Astronomical Observatory, * Szeged University KOLOS 2013

Sloan Digital Sky Survey (2000-…) First Standardized photometric system: Johnson’s UBV (1950…) Harold Lester Johnson (April 17, 1921 – April 2, 1980) UBV system: based on photomultipliers (basically blue-sensitive) Apache Point Observatory (New Mexico, US) D=2,5 m RC telescope – at 2788 m altitude 65% clear sky 3 deg. large field of view 30 x 4 Mpixels CCD (cooled to -80C LN)

Filterλc (Å)FWHM (Å) u' g' r' i' z' x58 mm Made by Omega Optical Supported by Masaryk Univ. Brno (Cz) & Szeged University (Hu)

Average scatter at Baja (July-August 2013)

SN 2012ht

SN 2013dy

SN 2013df

SN 2013ej

New griz photometry project: monitoring blazars in Kepler field 2541 BZBJ BL Lac 2606 BZQJ QSO RLoud flat radio sp BZBJ BL Lac 2635 BZBJ BL Lac Problem: there are no ‘griz’ standards near this area! Solution ???

One possible solution: usage of previous UBVRI standards and try to transform For Kepler-field blazars we selected NGC7790 open cluster’s standards. At the SDSS web site: One can find the possible linear formulae (Jordi et al., 2006) UBVRcIc -> ugriz ================ Transformation u-g = (0.750 ± 0.050)*(U-B) + (0.770 ± 0.070)*(B-V) + (0.720 ± 0.040) * g-V = (0.630 ± 0.002)*(B-V) - (0.124 ± 0.002) g-B = ( ± 0.002)*(B-V) - (0.124 ± 0.002) * g-r = (1.646 ± 0.008)*(V-R) - (0.139 ± 0.004) g-i = (1.481 ± 0.004)*(V-I) - (0.536 ± 0.004) if V-I <= 1.8 g-i = (0.83 ± 0.01)*(V-I) + (0.60 ± 0.03) if V-I > 1.8 * r-i = (1.007 ± 0.005)*(R-I) - (0.236 ± 0.003) * r-z = (1.584 ± 0.008)*(R-I) - (0.386 ± 0.005) r-R = (0.267 ± 0.005)*(V-R) + (0.088 ± 0.003) if V-R <= 0.93 r-R = (0.77 ± 0.04)*(V-R) - (0.37 ± 0.04) if V-R > 0.93 i-I = (0.247 ± 0.003)*(R-I) + (0.329 ± 0.002) (Jordi et al. (2006)

New experiment: another SDSS system on 50 cm RC telescope

Just for fun… ( BART-1, Baja Observatory, Hu Comet Lovejoy Thank you for your attention!