The three open clusters Be 15 , Be 80 , and NGC 2192 have been observed using CCD U BV ( RI ) _ { C } photometry at the San Pedro Mártir Observatory , México within the framework of our open-cluster survey .
The fundamental parameters of interstellar reddening , distance , and age have been derived , and also the metallicity for NGC 2192 ( solar metallicity has been assumed for the other two ) .
By shifting the colours of Schmidt-Kaler in the ( U – B,B – V ) two-colour diagram along the appropriate reddening vector , the interstellar reddenings have been derived as E ( B – V ) = 0.23 \pm 0.03 mag for Be 15 , 1.31 \pm 0.05 for Be 80 , and 0.16 \pm 0.03 for NGC 2192 .
Evidence is shown for a variable interstellar extinction across the cluster Be 80 .
For NGC 2192 a nicely consistent fit is obtained for both the interstellar reddening and the metallicity ( [ Fe / H ] = -0.31 ) using simultaneously the F-type and red-clump stars .

By fitting isochrones to the observed sequences of these three clusters in various colour–magnitude diagrams of different colour indices , ( B – V , V – I , or V – R ) the averages of distance moduli and heliocentric distances ( ( V – M _ { V } ) _ { o } ( mag ) ; d ( pc ) ) are the following : ( 10.74 \pm 0.01 ; 1202 ) for Be 15 , ( 10.75 \pm 0.01 ; 1413 ) for Be 80 , and ( 12.7 \pm 0.01 ; 3467 ) for NGC 2192 , and the averages of the inferred best ages ( \log ( { age } ) ; age ( Gyr ) ) are ( 8.6 \pm 0.05 ; 0.4 ) for Be 80 , and ( 9.15 \pm 0.05 ; 1.4 ) for NGC 2192 ; for Be 15 there are two distinct possibilities for the age fit , depending on the membership of three brighter stars , ( 9.35 or 9.95 \pm 0.05 ; 2.2 or 8.9 ) .
The need for spectroscopic observations in Be 15 is emphasized to select between alternate reddening and age solutions , and for deeper U BV observations in Be 80 to study in greater detail the variable interstellar , or intracluster , reddening across this cluster .