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#51
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Lat/Long and timekeeping system for Mars
On Thu, 06 Dec 2018 08:19:22 +0100, Paul Schlyter
wrote: The Hour Angle of a celestial object, which is needed to compute its local altitude and azimuth, is most easily computed by subtracting the object's RA from your local sidereal time. Of course you can compute your local sidereal time without labeling it as such or even without even being aware of what it is, but I don't see any convenient way around computing it if you compute the local altitude and azimuth for some celestial object. Sure, but that's exactly my point. We can understand the concept, but are still going to have a "huh?" moment if somebody talks about a "sidereal hour", simply because that's not a conventional term that anybody really uses. |
#52
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Lat/Long and timekeeping system for Mars
On Wed, 05 Dec 2018 13:00:32 -0500, Davoud wrote:
*Figuratively speaking. Due to macular degeneration I do not look through telescopes any more. I can still focus on a laptop display, however https://www.flickr.com/photos/primeval/30364292358, https://www.flickr.com/photos/primeval/29296501697. Very sorry to hear that. -- Email address is a Spam trap. |
#53
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Lat/Long and timekeeping system for Mars
On Thursday, December 6, 2018 at 8:21:17 AM UTC-7, Chris L Peterson wrote:
Sure, but that's exactly my point. We can understand the concept, but are still going to have a "huh?" moment if somebody talks about a "sidereal hour", simply because that's not a conventional term that anybody really uses. To me, I'd think that's a rather small "huh?" moment. If the sidereal time can be 16h 37m, then obviously when the sidereal time is 17h 37m, it must be one sidereal hour later - so the unit implicitly exists, even if it isn't normally explicitly mentioned. One thing that might appear paradoxical at first is this: Time zones on the Earth, ideally and abstractly, occupy 15 degrees of longitude. An hour of right ascension on the celestial sphere is also 15 degrees wide. So if you have two locations on the Earth, separated by 15 degrees of longitude, their solar time will differ by one hour; *and* their sidereal time will differ by one sidereal hour, which is shorter. Of course, there is no contradiction, because even in just one hour, the Earth will have moved in its orbit around the Sun. So an hour later, both locations will have advanced by 15 degrees in relation to the mean Sun, and both locations will have advanced by slightly more than 15 degrees in relation to the celestial sphere. John Savard |
#54
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Lat/Long and timekeeping system for Mars
On Tuesday, December 4, 2018 at 10:28:54 PM UTC-7, Quadibloc wrote:
On Tuesday, December 4, 2018 at 11:39:31 AM UTC-7, Gerald Kelleher wrote: I am sure the ISIS branch of astronomy would find 'sidereal vs solar' convictions acceptable We have not come to destroy, but to fulfill. And, at least if you go by the Julian calendar, fittingly enough, Sir Isaac Newton was born on Christmas Day. John Savard |
#55
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Lat/Long and timekeeping system for Mars
In a way I didn't notice the role of the International dateline in terms of timekeeping as one day elapses into the next or one rotation follows the last one.
This is the link to the calendar cycle as the continuous flow of days and rotations are sown up within the 1461/4 structure representing a close approximation to 365 1/4 rotations per orbital circuit. Something else to admire in how two different masterpieces fit together. |
#56
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Lat/Long and timekeeping system for Mars
Mike Collins wrote:
Quadibloc wrote: On Wednesday, December 5, 2018 at 10:03:26 PM UTC-7, palsing wrote: Gerald, are seriously suggesting that, for Mars, the hour, minute and second will be 'redefined' so that Mars will have a 24 hour rotation period? You are even more delusional than I thought! Why would this possible be an advantage in any way? In fact, *Robert Zubrin* suggested exactly the same thing. While the SI second will obviously be useful on Mars as everywhere else for defining the frequencies of radio waves, and so on and so forth, people living on Mars would want to have a way to refer to *the time of day*, and cutting the day, nearly as long as the day on Earth, into pieces following the same, familiar plan used on Earth is the simplest thing to do. John Savard Mars wris****ches have existed for years. They are used by the operators of Mars landers who need to start their shift times earlier every day. Since the first of these were slowed down Earth time watches they implicitly use Martian seconds. https://hackaday.com/2012/09/09/buil...sitys-drivers/ For human settlers on Mars I like the “witching hour” method of Vernor Vinge from Across Realtime where the standard Earth time is used with an extra period tagged onto the end of the day. But this would have problems with geographically (areographically) separated settlements. The simplest concepts are the easiest to get wrong. Later not earlier. |
#57
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Lat/Long and timekeeping system for Mars
On Thursday, December 6, 2018 at 11:40:50 AM UTC-7, Mike Collins wrote:
The simplest concepts are the easiest to get wrong. Later not earlier. Maybe you were thinking of the shorter sidereal day instead of the longer Martian day. John Savard |
#58
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Lat/Long and timekeeping system for Mars
On Thu, 06 Dec 2018 08:21:15 -0700, Chris L Peterson
wrote: On Thu, 06 Dec 2018 08:19:22 +0100, Paul Schlyter wrote: The Hour Angle of a celestial object, which is needed to compute its local altitude and azimuth, is most easily computed by subtracting the object's RA from your local sidereal time. Of course you can compute your local sidereal time without labeling it as such or even without even being aware of what it is, but I don't see any convenient way around computing it if you compute the local altitude and azimuth for some celestial object. Sure, but that's exactly my point. We can understand the concept, but are still going to have a "huh?" moment if somebody talks about a "sidereal hour", simply because that's not a conventional term that anybody really uses. There is always something new to learn.. |
#59
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Lat/Long and timekeeping system for Mars
On Thursday, December 6, 2018 at 2:09:42 PM UTC-8, Paul Schlyter wrote:
There is always something new to learn... Boy howdy, isn't that the truth... |
#60
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Lat/Long and timekeeping system for Mars
The system where the average 24 hour day anchored to the sunrise/noon/sunset cycle is converted into constant rotation at a rate of 15 degrees per hour has not been explained before nor has the system where the rotations are used seamless to create the calendar format of 365/366 days. They both come together as the masterpiece that is human timekeeping for those who can follow the close proximity between the planetary cycles and years, 24 days, equable hours, minutes and seconds.
https://www.youtube.com/watch?v=T-g27KS0yiY It may never happen that the same longitude system nor calendar framework is applied to Mars with its own unique timekeeping divisions on one side and the calendar format on the other but this will not be because the principles aren't there but rather the people who can accept them for Earth. What a lovely thing to do for people who can do it. |
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