We study the spectral properties in the range 3600Å - 6800Å of the nuclear region of galaxies behind the Magellanic Clouds .
The radial velocities clarified the nature of the objects as background galaxies or extended objects belonging to the Clouds .
For most galaxies behind the main bodies of the LMC and SMC , radial velocities were measured for the first time .
In the present sample typical LMC background galaxies are nearby ( 4000 < V ( { km / s } ) < 6000 ) , while SMC ’ s are considerably more distant ( 10000 < V ( { km / s } ) < 20000 ) .
We determine the reddening in each line of sight by matching a reddening-free galaxy template with comparable stellar population .
For the LMC main body we derive a combined Milky Way and internal reddening value E ( B-V ) _ { MW + i } = 0.12 \pm 0.10 , while for the SMC E ( B-V ) _ { MW + i } = 0.05 \pm 0.05 .
By subtracting Milky Way reddening values for galaxies projected onto the surroundings of each Cloud , we estimate average internal reddening values \Delta E ( B-V ) _ { i } = 0.06 and 0.04 , respectively for the main bodies of the LMC and SMC .
The Clouds are optically thin , at least in the directions of the studied background galaxies which are often difficult to be identified as such on ESO/SERC sky survey images .
Nevertheless , more reddened zones may occur where it is difficult to identify galaxies .