We present new spectroscopic and photometric data for 137 early-type galaxies in nine clusters , and for a set of nearby standard galaxies .
The clusters studied are Perseus ( A0426 ) , Pisces , A0262 , A0347 , J8 , HMS0122+3305 , 7S21 , A2199 and A2634 .

Our spectroscopic data comprise radial velocities ( cz ) , central velocity dispersions ( \sigma ) and magnesium line strength indices ( Mg _ { 2 } ) .
Internal errors ( derived from repeat observations ) are 7.6 per cent on each measurement of velocity dispersion , and 0.010 mag .
on each Mg _ { 2 } measurement .

Following Jørgensen et al. , we correct our \sigma and Mg _ { 2 } results to a physical aperture size of 1.19 h \mbox { $ { } ^ { -1 } $ } kpc .
We correct the major published datasets to the same aperture size , and define a new ‘ standard system ’ by the aperture-corrected Lick data of Davies et al .
Through extensive intercomparisons with data from the literature , we present the corrections required to bring the major published datasets onto the standard system .
The uncertainty in these corrections is computed .
We demonstrate that our new velocity dispersion data can be brought into consistency with the standard system , to an uncertainty of \mathrel { \hbox { \hbox to 0.0 pt { \hbox { \lower 4.0 pt \hbox { $ \sim$ } } } \hbox { $ < $ } } } 0.01 dex .

From R-band CCD photometry , we derive effective diameter ( A _ { e } ) , mean surface brightness within effective diameter ( \langle \mu \rangle _ { e } ) and an R-band diameter equivalent to the D _ { n } parameter of Dressler et al .
Internal comparisons indicate an average error of 0.005 in each measurement of log D _ { n } .
The combination \log A _ { e } -0.3 \langle \mu \rangle _ { e } , approximately the quantity used in the Fundamental Plane distance indicator , has an uncertainty of 0.006 per measurement .
The photometric data can be brought onto a system consistent with external data at the level of 0.5 per cent in distance .

These data will be used in a companion paper , to derive distance and peculiar velocity estimates for the nine clusters studied .