EIT Observations of the 15 November 1999 Mercury Transit

The Mercury transit of 15 November 1999 has been observed from space by the SOHO and TRACE spacecraft. We exploited the data recorded by EIT/SOHO to determine the stray-light level and the plate-scale of the instrument. The asymmetric distribution of stray light across the images is confirmed, but the absolute amount was found to be higher than previously estimated. The plate scale averaged over wavelengths was found to be 2.627±0.001 arc sec pixel −1 , in excellent agreement with two previous and independent determinations.