John O’Neill


Yes Peter, that’s the USNO link I relied on for years, but in my brower (Firefox), it’s broken.

Just to be clear, the quantity, I was after, is Delta T = (TT – UT), where TT is Terrestrial Time and UT is Universal Time.

In J.Meeus Astronomical Algorithms 2nd Ed page 77 he states “The exact value of the difference Delta-T = TD – UT can be deducted only from observations”. I assume, for my purposes, TD and TT are interchangeable.