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General Astronomy >> General Observing and Astronomy

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rnc39560
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Reged: 07/23/13

Loc: MS coast
decimal degrees or degrees and minutes? *DELETED*
      #6185128 - 11/09/13 05:35 PM

Post deleted by rnc39560

Edited by rnc39560 (11/09/13 06:38 PM)


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SkipW
sage


Reged: 02/03/11

Loc: Oklahoma, USA
Re: decimal or degrees? new [Re: rnc39560]
      #6185139 - 11/09/13 05:42 PM

?

Location latitude and longitude are almost always specified in degrees. Do you mean degrees and minutes vs. decimal degrees?


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rnc39560
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Re: decimal or degrees? new [Re: SkipW]
      #6185229 - 11/09/13 06:35 PM

Yes, that's what I meant. I should've been more specific. There, fixed it. Thanks.

Edited by rnc39560 (11/09/13 06:39 PM)


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SkipW
sage


Reged: 02/03/11

Loc: Oklahoma, USA
Re: decimal or degrees? new [Re: rnc39560]
      #6189783 - 11/11/13 11:54 PM

Degrees, minutes and seconds are traditional but are a pain to work with. Degrees and decimal minutes are not unusual. Decimal degrees are easiest to work with and becoming more common.

None are wrong; what are you trying to do?


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rnc39560
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Re: decimal or degrees? new [Re: SkipW]
      #6190180 - 11/12/13 08:55 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.

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Tony Flanders
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Re: decimal or degrees? new [Re: rnc39560]
      #6190188 - 11/12/13 09:07 AM

Quote:

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.


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rnc39560
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Re: decimal or degrees? new [Re: Tony Flanders]
      #6190250 - 11/12/13 09:54 AM

Thanks Tony.

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PeterR280
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Re: decimal or degrees? new [Re: rnc39560]
      #6190275 - 11/12/13 10:06 AM

Longer time periods should be based on fortnights.

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SkipW
sage


Reged: 02/03/11

Loc: Oklahoma, USA
Re: decimal or degrees? new [Re: PeterR280]
      #6191785 - 11/12/13 10:37 PM

Great suggestion! The fortnight is, I think, the longest period of time with a constant length.

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Starry eyes
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Re: decimal or degrees? new [Re: SkipW]
      #6191851 - 11/12/13 11:17 PM

I'd like to point out that as a sailor we use one minute of latitude equal to one nautical mile. Also as a surveyor we use minutes & seconds as a matter of course. Also 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. So these units are tied to fundamental properties of our Earth.

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brianb11213
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Re: decimal or degrees? new [Re: PeterR280]
      #6192041 - 11/13/13 03:52 AM

Quote:

Longer time periods should be based on fortnights.



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.

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.


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Tony Flanders
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Re: decimal or degrees? new [Re: Starry eyes]
      #6192136 - 11/13/13 07:49 AM

Quote:

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.

Quote:

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.


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Retsub
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Reged: 12/08/06

Loc: Houston,Tx.
Re: decimal or degrees? new [Re: Tony Flanders]
      #6193847 - 11/14/13 12:55 AM

Wasn't it from those same people that we now use the wheel width for our cho-cho train tracks ? Thanks. *BW*

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