If you are talking regular old fire than copper is fine. It will tolerate nearly 1,900 degrees F if I’m not mistaken. It will probably burn through whatever you rest it on long before the copper gets hot enough to melt.
Are you talking planetary hours? which day of the week, what day of the year? It changes every day. Take the time from sunrise to sunset, divide that number by twelve. Figure out which hour Jupiter falls on that day and and multiply the first number by the second. Then, starting with the time of sunrise, count ahead an amount of minutes equal to that total. This is the start of the planetary hour. It ends after as many minutes have passed as your first number. Same process for night, just sunset to sunrise the following week day.