I thought that Waugh had taken a mid-leap-year cycle as the starting point for most of his data so that the figures for declination and EoT would be a fair average; indeed, in his text alongside the EoT scale I believe he says that they ARE averages and also he mentions the typical errors that might result from using this table. I suspect that he chose to mention Feb 29th so his table would be of near 'universal' use and that he chose the stated figures so that the errors would still lie within the bounds that he mentions.
Apart from the possibility that there may be a mistake in Waugh's workings - I haven't done my own check of his data - I doubt that you can see a significant improvement from using another appraoch. There is no one table that is correct for all years simply because we do not use a calendar that properly matches the sun's apparent motion except over the full leap year cycle of several hundred years. However the errors in question are usually small in comparison with the other errors of design and setup of a dial - not to mention those of the difficulty in deciding where a shadow is from the umbra and penumbra! It's possible that as we get away from the Year 2000 which of course is a special and non-standard leap year (it involving the leap year correction that occurs only every 400 years) it may be possible to draft a better table but I suspect not for many years yet. Patrick
