decimal degrees or degrees and minutes? *DELETED*
Posted 09 November 2013 - 05:42 PM
Location latitude and longitude are almost always specified in degrees. Do you mean degrees and minutes vs. decimal degrees?
Posted 09 November 2013 - 06:35 PM
Posted 11 November 2013 - 11:54 PM
None are wrong; what are you trying to do?
Posted 12 November 2013 - 08:55 AM
Posted 12 November 2013 - 09:07 AM
Was just curious. I have seen both used occasionally, and was wondering WHICH seemed to be more understood and which was more often used.
Both are very common. To make matters worse, right ascension (RA) is sometimes measured in hours and sometimes in degrees, where 1 hour = 15 degrees.
It's just another example of the glorious lack of standardization that makes astronomy so entertaining.
If you think about it, it's pretty mind-boggling that despite massive inconvenience we're still using a base-60 system for angular measures whose heyday was in ancient Sumeria. It was already obsolete by the time the Greeks adopted it 2,500 years ago.
Posted 12 November 2013 - 10:37 PM
Posted 12 November 2013 - 11:17 PM
Posted 13 November 2013 - 03:52 AM
Funny you should bring this up. Timings for DEC computers (PDP, VAX - remember them?) were usually quoted in microfortnights (a little larger than a second). Really confused anyone not in the know.
Longer time periods should be based on fortnights.
I don't see why "long" periods should not be measured in megaseconds (approx. 11.6 days), gigaseconds (approx. 31.7 years), teraseconds & petaseconds. The current age of the solar system is approximately 142 Ps & even the age of the universe (430 Ps) is not sufficiently long to make the exasecond a practical unit for "historical" events, though the Es is insufficient for projections of cosmological evolution into the distant future.
Posted 13 November 2013 - 07:49 AM
I'd like to point out that as a sailor we use one minute of latitude equal to one nautical mile.
True -- that's a very handy fact, useful for anybody (like me) who plays mentally with latitude and longitude. However, the fact that one sixtieth of one 360th of a meridian on Earth happens to be approximately the same as 1,000 full paces of the Roman army is entirely coincidental. Neither the Sumerians nor the Romans were aware of that fact when they established their respective measures.
One R.A. " is the angular distance in R.A. traversed in one R.A. second of time which is tied to the rotational period of the Earth.
Yes, of course. Measuring R.A. in time isn't arbitrary at all -- though measuring time in sixtieths gets us right back to those Sumerians again.
Posted 14 November 2013 - 12:55 AM