Spatially nonuniform electrodeposition can cause discrepancies between predicted and experimentally measured mass loadings on an electrochemical quartz crystal microbalance (EQCM) since the sensitivity of the quartz crystal varies significantly from point to point. These discrepancies can be significant even if the current distribution is nearly uniform. These effects were examined experimentally by varying the conductivity of the electrolyte and the current density during the electrodeposition of copper on an EQCM, effecting changes in the spatial, deposited-mass distribution in a controlled manner. The resulting frequency shifts are in agreement with results predicted by current distribution simulations, validated a posteriori with profilometry measurements. Our results permit determination of the spatial variation of the quartz crystal sensitivity factor or of the current distribution on the EQCM.

Late in 1988 the Mt John University Observatory acquired a cryogenic CCD system from Photometrics Ltd (Tucson). The chip is a Thomson CSF TH7882 CDA comprising 384 × 576 pixels. As part of the evaluation process, we have begun two differential photometry programs of the Magellanic Clouds using the Mt John 0.6m Boller & Chivens telescope. On this telescope each CCD pixel corresponds to 0.6 arcsec. Mt John's southerly latitude (44°S) permits year-round observations of the Clouds.

The first program concerns B, V and I photometry of five blue eclipsing binaries selected, on the basis of Gaposchkin's (1970, 1977) photographic light curves, to have roughly equal components with minimal interaction. HV 12634 has also been observed for comparison with the CCD light curves published by Jensen et al. (1988). Fig. 1 shows the B observations so far obtained for HV 1761, but the reduction is preliminary, being based on aperture-integrated magnitudes. The field is populous, and a final reduction will require use of a crowded-field reduction package such as ROMAFOT.