Goodnes, how far off topic are we? But here goes. Rule of thumb for tide rise; Take the total rise from low water to high water. Then in the first hour the tide will rise 1/12 of the total; in the second, 2/12; in the third, 3/12; in the fourth, 3/12; in the fifth, 2/12 and in the sixth hour, 1/12. Inaccurate but useful.
Not a rule of thumb but how I see sidereal time. Roll a penny or cent once around another. The rolling coin turns twice (1 plus 1) in its journey. Roll an earth around a sun 365 times. The earth rotates 366 (365 plus 1) times. So a sidereal day is 365/366 of 24 hours which is 23h. 56m. 4s. Frank 55N 1W -- Frank Evans
