  At the Universitaetssternwarte Bochum near Cerro Armazones we have monitored
the Seyfert-1 galaxy 3C 120 between September 2014 and March 2015 in BVRI and a
narrow band filter covering the redshifted H alpha line; in addition we
obtained a single con-temporary spectrum with FAST at Mt. Hopkins. Compared to
earlier epochs 3C 120 is about a factor of three brighter, allowing us to study
the shape of the broad line region (BLR) and the dust torus in a high
luminosity phase. The analysis of the light curves yields that the dust echo is
rather sharp and symmetric in contrast to the more complex broad H alpha BLR
echo. We investigate how far this supports an optically thick bowl-shaped BLR
and dust torus geometry as proposed by Kawaguchi & Mori (2010) and Goad et al.
(2012). The comparison with several parameterizations of these models supports
the following geometry: the BLR clouds lie inside the bowl closely above the
bowl rim, up to a half covering angle 0 deg < theta < 40 deg (measured against
the equatorial plane). Then the BLR is spread over many isodelay surfaces,
yielding a smeared and structured echo as observed. Furthermore, if the BLR
clouds shield the bottom of the bowl rim against radiation from the nucleus,
the hot dust emission comes essentially from the top edge of the bowl (40 deg <
theta < 45 deg). Then, for small inclinations as for 3C120, the top dust edge
forms a ring which largely coincides with a narrow range of isodelay surfaces,
yielding the observed sharp dust echo. The scale height of the BLR increases
with radial distance from the black hole. This leads to luminosity dependent
foreshortening effects of the lag. We discuss implications and possible
corrections of the foreshortening for the black hole mass determination and
consequences for the lag (size) - luminosity relationships and the difference
to interferometric torus sizes.
