We present the catalogue of a wide-field CFHT/WHT spectroscopic survey of the lensing cluster Cl0024+1654 at z=0.395. This catalogue contains 618 new spectra, of which 581 have identified redshifts. Adding redshifts available from the literature, the final

12O.Czoskeetal.:SpectroscopicsurveyofCl0024:I.The

catalogue

Fig.4h.Continued

TheprimarycriterionforthecandidateselectionforthespectroscopicsurveywasV<23.ThecompletenessinVmagnitudeofthe nalcatalogueisshowninFig.6,whereforeachgalaxyfromthespectroscopiccataloguewecountthenumberofobjectsinabinof±0.25magaroundthegalaxymagnitudeinboththespectroscopicandpho-tometriccatalogues(thelatterrestrictedtothesurveyareaasoutlinedinFig.7)andde netheirratioastheto-talcompletenessatthegivenmagnitude.BetweenV 20andV 22thecompletenessisroughlyconstantat～45%anddropsrapidlyforfaintermagnitudes.Restrictingthesameanalysistothecentralareawithin3′oftheclustercentre(usinglargerbinsof±0.5mag)showsthatinthisregionthecompletenessexceeds80%betweenV 20andV 22.

Avisualimpressionofthevariationofthecomplete-nessacrossthesurveyareaisgiveninFig.7whereweuseanadaptivetop-hat(itsradiusatanygivenpointofagridisthegeometricmeanofthedistancestothe10thand11thnearestobjectswithspectroscopy)tocomputetheratioofthenumbersofobjectswithspectroscopy( xedto10)andthenumberofobjectsinthephotometriccata-logue.Inordertohavesampleswithwell-de ned(thoughaposteriori)photometricselectionlimitswerestrictthespectroscopicandphotometriccataloguesforthispurposetosubsampleswith20<V<23and0.6<V I<2.4.AsFig.5shows,thisregionofthecolour-magnitudeplaneenclosesvirtuallyalltheclustermembersinthespectro-scopiccatalogue.Withinourrestrictedsamplethesepa-rationbetweenstarsandgalaxieswithinthephotomet-riccatalogueisfairlystraightforwardusingSExtractor’sCLASS

zN=0.4921and