A first set of 14 visually good candidate clusters associated with pointlike NVSS radio sources have been observed with the 3.6 m ESO telescope at La Silla, with the EFOSC1 spectrograph in multislit mode. Moreover, photometry of each field in the r-Gunn filter has been acquired during the first night of observation to achieve magnitude $r \simeq 22.5$ - corresponding to roughly $b_{\rm J} \sim 24$ - with a photometric accuracy better than 0.2 mag.

The targets for spectroscopic observations were chosen on the basis of these photometric observations. For 12 candidate clusters the spectra of the radiogalaxy and about 10-14 companions were acquired. Observations were made with the B300 grism, characterized by a wavelength range 3740-6950 Å, central wavelength $\lambda_{\rm c} =$ 5250 Å and dispersion 230 Å mm^-1. The slit width was chosen to be $2.1\hbox{$^{\prime\prime}$ }$ while the slit length varied in order to optimize the number of acquired spectra. The resolution on the spectra was about 20 Å.

Table 1: Measured velocities and r-Gunn magnitudes for galaxies in the 12 observed cluster candidates. Notes: "R'' = radiogalaxy; "E'' = emission line galaxy; " $\ast$ '' = star.
NAME N $m_{\rm r}$ v $\sigma _{\rm v}$ Notes

${\rm (km~s^{-1})}$ ${\rm (km~s^{-1})}$

294N15 1 19.69 89125 $\pm$ 86

2 19.09 92061 $\pm$ 60

3 17.67 19572 $\pm$ 300 E

4 17.42 90363 $\pm$ 41 R

5 19.78 85666 $\pm$ 122

6 20.10 - -

7 18.55 89065 $\pm$ 50

8 20.05 89540 $\pm$ 46

9 15.62 21186 $\pm$ 48

10 20.53 61998 $\pm$ 100

11 20.13 - -

12 20.33 90960 $\pm$ 259

295N35 1 20.90 - -

2 19.50 23511 $\pm$ 130

3 19.68 31000 $\pm$ 300

4 19.08 79401 $\pm$ 309

5 19.53 97000 $\pm$ 300

6 20.10 78568 $\pm$ 107

7 17.84 79110 $\pm$ 379 R

8 21.29 14800 - E

9 - - -

10 20.51 98925 $\pm$ 114

11 18.38 79863 $\pm$ 198

349N02 1 19.59 34237 $\pm$ 300

2 18.80 29093 $\pm$ 130

3 18.81 63333 $\pm$ 85

4 - - -

5 18.42 - - $\ast$

6 16.03 33698 $\pm$ 49 R

7 18.83 - - $\ast$

8 19.69 123966 $\pm$ 300 E

9 20.84 146819 $\pm$ 300 E

10 21.45 - -

350N71 1 16.97 42919 $\pm$ 74

2 17.16 42586 $\pm$ 86

3 20.62 80696 $\pm$ 112

4 17.73 69681 $\pm$ 169

5 16.23 56290 $\pm$ 80

6 18.79 56099 $\pm$ 280

7 17.80 69904 $\pm$ 109

8 17.91 70484 $\pm$ 82 R

9 18.44 70824 $\pm$ 119

10 18.36 70060 $\pm$ 121

352N47 1 19.77 51980 $\pm$ 137

2 16.68 51988 $\pm$ 114 R

3 19.60 81249 $\pm$ 258

4 18.06 51233 $\pm$ 150

5 20.85 - -

6 18.70 52499 $\pm$ 150

7 20.02 86464 $\pm$ 300

8 19.63 63814 $\pm$ 220

9 19.90 97518 $\pm$ 172

10 19.81 - -

**Table 1:** Measured velocities and r-Gunn magnitudes for galaxies in the 12 observed cluster candidates. Notes: "R'' = radiogalaxy; "E'' = emission line galaxy; " $\ast$ '' = star.
NAME	N	$m_{\rm r}$	v	$\sigma _{\rm v}$	Notes
			${\rm (km~s^{-1})}$	${\rm (km~s^{-1})}$
294N15	1	19.69	89125	$\pm$ 86
	2	19.09	92061	$\pm$ 60
	3	17.67	19572	$\pm$ 300	E
	4	17.42	90363	$\pm$ 41	R
	5	19.78	85666	$\pm$ 122
	6	20.10	-	-
	7	18.55	89065	$\pm$ 50
	8	20.05	89540	$\pm$ 46
	9	15.62	21186	$\pm$ 48
	10	20.53	61998	$\pm$ 100
	11	20.13	-	-
	12	20.33	90960	$\pm$ 259
295N35	1	20.90	-	-
	2	19.50	23511	$\pm$ 130
	3	19.68	31000	$\pm$ 300
	4	19.08	79401	$\pm$ 309
	5	19.53	97000	$\pm$ 300
	6	20.10	78568	$\pm$ 107
	7	17.84	79110	$\pm$ 379	R
	8	21.29	14800	-	E
	9	-	-	-
	10	20.51	98925	$\pm$ 114
	11	18.38	79863	$\pm$ 198
349N02	1	19.59	34237	$\pm$ 300
	2	18.80	29093	$\pm$ 130
	3	18.81	63333	$\pm$ 85
	4	-	-	-
	5	18.42	-	-	$\ast$
	6	16.03	33698	$\pm$ 49	R
	7	18.83	-	-	$\ast$
	8	19.69	123966	$\pm$ 300	E
	9	20.84	146819	$\pm$ 300	E
	10	21.45	-	-
350N71	1	16.97	42919	$\pm$ 74
	2	17.16	42586	$\pm$ 86
	3	20.62	80696	$\pm$ 112
	4	17.73	69681	$\pm$ 169
	5	16.23	56290	$\pm$ 80
	6	18.79	56099	$\pm$ 280
	7	17.80	69904	$\pm$ 109
	8	17.91	70484	$\pm$ 82	R
	9	18.44	70824	$\pm$ 119
	10	18.36	70060	$\pm$ 121
352N47	1	19.77	51980	$\pm$ 137
	2	16.68	51988	$\pm$ 114	R
	3	19.60	81249	$\pm$ 258
	4	18.06	51233	$\pm$ 150
	5	20.85	-	-
	6	18.70	52499	$\pm$ 150
	7	20.02	86464	$\pm$ 300
	8	19.63	63814	$\pm$ 220
	9	19.90	97518	$\pm$ 172
	10	19.81	-	-

Table 1: continued.
NAME N $m_{\rm r}$ v $\sigma _{\rm v}$ Notes

${\rm (km~s^{-1})}$ ${\rm (km~s^{-1})}$

352N63 1 18.23 54587 $\pm$ 71

2 19.01 55881 $\pm$ 189

3 21.28 - -

4 20.07 - -

5 16.73 54698 $\pm$ 118

6 18.38 54699 $\pm$ 76 R

7 18.29 53486 $\pm$ 84

8 18.74 55275 $\pm$ 78

9 20.60 - -

10 20.32 - -

11 19.85 - -

352N75 1 19.57 - -

2 18.91 40809 $\pm$ 144

3 18.41 40764 $\pm$ 62

4 18.59 54726 $\pm$ 131

5 19.18 55821 $\pm$ 271

6 16.15 55316 $\pm$ 123

7 16.59 40492 $\pm$ 63 R

8 18.63 41140 $\pm$ 68

9 20.11 - -

10 18.04 - -

11 18.16 - - $\ast$

12 18.43 37199 $\pm$ 151

13 17.60 40377 $\pm$ 54

14 20.33 - -

409N03 1 18.15 64532 $\pm$ 127

2 17.44 47583 $\pm$ 429

3 16.38 41309 $\pm$ 50 R

4 20.01 - -

5 20.15 46345 $\pm$ 145

6 17.65 46765 $\pm$ 61

7 15.89 47150 $\pm$ 55

8 18.30 46879 $\pm$ 57

9 20.31 - -

10 19.46 47460 $\pm$ 247

11 19.83 46630 $\pm$ 457

12 19.62 - -

409N15 1 20.06 97958 $\pm$ 75

2 17.44 45837 $\pm$ 39

3 18.74 45687 $\pm$ 42

4 18.54 45682 $\pm$ 46

5 16.62 45280 $\pm$ 31 R

6 20.43 85363 $\pm$ 98 E

7 19.00 45343 $\pm$ 58

8 20.53 38136 $\pm$ 79

9 20.67 43891 $\pm$ 100 E

10 19.98 78625 $\pm$ 65

11 19.59 79383 $\pm$ 165

409N44 1 19.80 98238 $\pm$ 172

2 20.02 69000 $\pm$ 200

3 19.91 41416 $\pm$ 158

4 17.62 40147 $\pm$ 61 R

5 19.69 41300 $\pm$ 300

6 18.07 58828 $\pm$ 73

7 17.71 40332 $\pm$ 74

8 18.18 39350 $\pm$ 42

**Table 1:** continued.
NAME	N	$m_{\rm r}$	v	$\sigma _{\rm v}$	Notes
			${\rm (km~s^{-1})}$	${\rm (km~s^{-1})}$
352N63	1	18.23	54587	$\pm$ 71
	2	19.01	55881	$\pm$ 189
	3	21.28	-	-
	4	20.07	-	-
	5	16.73	54698	$\pm$ 118
	6	18.38	54699	$\pm$ 76	R
	7	18.29	53486	$\pm$ 84
	8	18.74	55275	$\pm$ 78
	9	20.60	-	-
	10	20.32	-	-
	11	19.85	-	-
352N75	1	19.57	-	-
	2	18.91	40809	$\pm$ 144
	3	18.41	40764	$\pm$ 62
	4	18.59	54726	$\pm$ 131
	5	19.18	55821	$\pm$ 271
	6	16.15	55316	$\pm$ 123
	7	16.59	40492	$\pm$ 63	R
	8	18.63	41140	$\pm$ 68
	9	20.11	-	-
	10	18.04	-	-
	11	18.16	-	-	$\ast$
	12	18.43	37199	$\pm$ 151
	13	17.60	40377	$\pm$ 54
	14	20.33	-	-
409N03	1	18.15	64532	$\pm$ 127
	2	17.44	47583	$\pm$ 429
	3	16.38	41309	$\pm$ 50	R
	4	20.01	-	-
	5	20.15	46345	$\pm$ 145
	6	17.65	46765	$\pm$ 61
	7	15.89	47150	$\pm$ 55
	8	18.30	46879	$\pm$ 57
	9	20.31	-	-
	10	19.46	47460	$\pm$ 247
	11	19.83	46630	$\pm$ 457
	12	19.62	-	-
409N15	1	20.06	97958	$\pm$ 75
	2	17.44	45837	$\pm$ 39
	3	18.74	45687	$\pm$ 42
	4	18.54	45682	$\pm$ 46
	5	16.62	45280	$\pm$ 31	R
	6	20.43	85363	$\pm$ 98	E
	7	19.00	45343	$\pm$ 58
	8	20.53	38136	$\pm$ 79
	9	20.67	43891	$\pm$ 100	E
	10	19.98	78625	$\pm$ 65
	11	19.59	79383	$\pm$ 165
409N44	1	19.80	98238	$\pm$ 172
	2	20.02	69000	$\pm$ 200
	3	19.91	41416	$\pm$ 158
	4	17.62	40147	$\pm$ 61	R
	5	19.69	41300	$\pm$ 300
	6	18.07	58828	$\pm$ 73
	7	17.71	40332	$\pm$ 74
	8	18.18	39350	$\pm$ 42

Table 1: continued.
NAME N $m_{\rm r}$ v $\sigma _{\rm v}$ Notes

${\rm (km~s^{-1})}$ ${\rm (km~s^{-1})}$

9 18.26 58805 $\pm$ 195

412N23 1 20.40 29350 $\pm$ 300

2 19.81 49474 $\pm$ 110

3 17.69 77698 $\pm$ 144 R

4 17.13 48980 $\pm$ 80

5 19.14 32075 $\pm$ 200

6 16.88 30590 $\pm$ 300

7 18.78 76139 $\pm$ 98

8 20.83 - -

9 19.84 47521 $\pm$ 78 E

10 19.07 29934 $\pm$ 57

11 19.52 60417 $\pm$ 300

475N50 1 18.99 61683 $\pm$ 84

2 19.86 64065 $\pm$ 300

3 18.24 62720 $\pm$ 300

4 18.59 63050 $\pm$ 300

5 17.98 61318 $\pm$ 94

6 17.34 63758 $\pm$ 130

7 17.98 64280 $\pm$ 173

8 17.49 63160 $\pm$ 108 R

9 20.79 - -

10 19.62 63421 $\pm$ 124

11 19.47 - - $\ast$

12 19.33 64246 $\pm$ 118

**Table 1:** continued.
NAME	N	$m_{\rm r}$	v	$\sigma _{\rm v}$	Notes
			${\rm (km~s^{-1})}$	${\rm (km~s^{-1})}$
	9	18.26	58805	$\pm$ 195
412N23	1	20.40	29350	$\pm$ 300
	2	19.81	49474	$\pm$ 110
	3	17.69	77698	$\pm$ 144	R
	4	17.13	48980	$\pm$ 80
	5	19.14	32075	$\pm$ 200
	6	16.88	30590	$\pm$ 300
	7	18.78	76139	$\pm$ 98
	8	20.83	-	-
	9	19.84	47521	$\pm$ 78	E
	10	19.07	29934	$\pm$ 57
	11	19.52	60417	$\pm$ 300
475N50	1	18.99	61683	$\pm$ 84
	2	19.86	64065	$\pm$ 300
	3	18.24	62720	$\pm$ 300
	4	18.59	63050	$\pm$ 300
	5	17.98	61318	$\pm$ 94
	6	17.34	63758	$\pm$ 130
	7	17.98	64280	$\pm$ 173
	8	17.49	63160	$\pm$ 108	R
	9	20.79	-	-
	10	19.62	63421	$\pm$ 124
	11	19.47	-	-	$\ast$
	12	19.33	64246	$\pm$ 118

5.1 Data reduction

Multislit spectroscopic data reduction has been made interactively by means of the IRAF package. Reduction steps involved bias subtraction, spectra extraction, spectra wavelength calibration. We found no need to correct for dark current. This procedure has been applied both to astronomical and to calibration lamps exposures.

We acquired a total number of 129 galaxy spectra, plus 4 stars, for 12 successfully observed candidates, and determined the velocity of galaxies from absorption and, in a few cases, emission lines by means of the RVSAO package. None of the radiogalaxies we observed show emission lines in their spectra. Templates for the cross-correlation consist of 8 galaxy and 8 star spectra known from previous observative programs: the 8 galaxies were observed during the Edinburgh-Milano Cluster Survey (Collins et al. 1995) with EFOSC1 and with the same spectral resolution as our observations. The 8 stars come from ESO Slice Project (Vettolani et al. 1997) observations with the fiber spectrograph OPTOPUS.

To allow for cleaning of cosmic rays, multiple exposures were taken for each field, for a total exposure time varying from 40 to 60 min. In Fig. 3 the direct imaging exposures of these 12 candidates are shown, together with the targets we selected for spectroscopy.

In Table 1 the r-Gunn magnitudes, the measured velocities and their associated errors are given for each galaxy we observed in the selected candidate clusters. As can be seen from Table 1, for 22 out of the 129 observed galaxies the S/N was not good enough to measure the redshift. The typical r magnitude for galaxies with measured redshift is 18.7. Stars are marked with an asterisk. The high errors associated to some velocity measurements are mainly due to the low spectral S/N.

5 Optical observations

5.1 Data reduction