A pilot study with the new powerful backend of the Westerbork Synthesis Radio Telescope ( WSRT ) of two galaxy clusters at z=0.2 has revealed neutral hydrogen emission from 39 galaxies .
At these redshifts , the WSRT provides an instantaneous velocity coverage of 18,054 km/s .
The volume probed for each cluster is 1.7 \times 10 ^ { 4 } Mpc ^ { 3 } , with spatial and velocity resolutions of 54 \times 86 kpc ^ { 2 } and 19.7 km/s , covering both clusters and the large scale structure in which they are embedded .

The spatial distribution of the H I detected galaxies is very different for the two clusters .
In Abell 963 , most of the gas rich galaxies are located to the northeast , at 1 - 3 Mpc from the cluster center in projection .
Their velocities are slightly redshifted with respect to the cluster mean .
This could be a gas rich group falling in from the front .
Abell 2192 is less massive and more diffuse , with the gas rich galaxies more uniformly spread over a large region around the cluster .
The H I masses of the detected galaxies range from 5 \times 10 ^ { 9 } to 4 \times 10 ^ { 10 } M _ { \odot } .
Some H I rich galaxies are spatially resolved and rudimentary rotation curves are derived , showing the prospect for Tully-Fisher studies of different galaxy populations in these environments .

Only one galaxy is detected within a 1 Mpc radius from the center of the Butcher-Oemler cluster Abell 963 , and none of the blue B-O galaxies which are all located within the central Mpc .
The H I detected galaxies outside the central Mpc are of similar colour and magnitude as the non-detected B-O galaxies , indicating that the blue B-O galaxies are gas poor compared to their counterparts in the field .