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The UTC thread



 
 
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  #1  
Old August 14th 04, 04:26 PM
MikeThomas
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Default The UTC thread

It should be quite clear to anyone in astronomy by now that UT or UTC or GMT
is Universal Time. Those who don't have any concept of this designation
should
really consider just what level of amateur they really are. Astronomical
observing
is completely dependent on timing. It is just easier if people report
observations of any kind
in UTC. People should know what their local offset is whether it is
Daylight or standard, PDT, MST, MDT,EDT,Europe, China or Antartica!!

For one thing, to do a polar alignment, you have to know your local time
meridian offset and whether you
are east or west of it.


  #2  
Old August 14th 04, 04:48 PM
Chuck
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For those of us who do orbital mechanics for a living, UT, UTC and GMT is
just the beginning... But you don't need to know any of those things to
discover a comet, make a new observation on a variable star, discover a new
supernova, etc. Let's not degrade other people because making time
conversions makes you irritable...

--

Clear Skies,

Chuck

"MikeThomas" wrote in message
news:6bqTc.20328$fz2.3652@edtnps89...
It should be quite clear to anyone in astronomy by now that UT or UTC or

GMT
is Universal Time. Those who don't have any concept of this designation
should
really consider just what level of amateur they really are. Astronomical
observing
is completely dependent on timing. It is just easier if people report
observations of any kind
in UTC. People should know what their local offset is whether it is
Daylight or standard, PDT, MST, MDT,EDT,Europe, China or Antartica!!

For one thing, to do a polar alignment, you have to know your local time
meridian offset and whether you
are east or west of it.




  #3  
Old August 14th 04, 05:14 PM
MikeThomas
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"Sam Wormley" wrote in message
...
MikeThomas wrote:

It should be quite clear to anyone in astronomy by now that UT or UTC or

GMT
is Universal Time.


Except there are subtle differences between those three that astronomers
should definitely know.

See: http://www.edu-observatory.org/gps/time.html
http://scienceworld.wolfram.com/astr...ersalTime.html

Innovation: GPS and Leap Seconds, Time to Change?,
GPS World, Nov 1999


Look, I am not referring to astronauts and space exploration. You are
splitting hairs. Why don't you
offer up some useful information?


  #4  
Old August 14th 04, 06:32 PM
Etok
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MikeThomas wrote:

It should be quite clear to anyone in astronomy by now that UT or UTC or GMT
is Universal Time. Those who don't have any concept of this designation
should
really consider just what level of amateur they really are. Astronomical

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^
observing
is completely dependent on timing. It is just easier if people report
observations of any kind
in UTC. People should know what their local offset is whether it is
Daylight or standard, PDT, MST, MDT,EDT,Europe, China or Antartica!!

For one thing, to do a polar alignment, you have to know your local time
meridian offset and whether you
are east or west of it.



Please tell us, Mike, what level of amateur are YOU?

Regards,
Etok

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  #5  
Old August 14th 04, 07:08 PM
John Beaderstadt
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While reading in the bathroom on Sat, 14 Aug 2004 15:26:58 GMT, I saw
that "MikeThomas" had written:

For one thing, to do a polar alignment, you have to know your local time
meridian offset and whether you
are east or west of it.


????????????

To do a polar alignment, I line up on the pole star. Time has nothing
to do with it, although knowing how to put my 'scope in its "home"
position is critical.

For a planisphere, with the amount of light pollution around here, I
can be as much as an hour off without screwing up my ability to find
something in the sky.

For using Autostar on my goto (ETX-125), accuracy to within a couple
of minutes is adequate. You do have to know your time zone, and
whether you're in daylight or standard time, but even the exact
long-lat isn't necessary.

I do have the knowledge and capability to be more precise than that
but, as someone else said, we're not astronauts, and astronomy isn't
rocket science. The night sky doesn't move that fast and a
wide-enough FOV will give you plenty of margin.


--------------
Beady's Corollary to Occam's Razor: "The likeliest explanation of any phenomenon is almost always the most boring one imaginable."


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  #6  
Old August 14th 04, 07:40 PM
Chris L Peterson
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On Sat, 14 Aug 2004 14:08:01 -0400, John Beaderstadt wrote:

I do have the knowledge and capability to be more precise than that
but, as someone else said, we're not astronauts, and astronomy isn't
rocket science. The night sky doesn't move that fast and a
wide-enough FOV will give you plenty of margin.


My telescope pointing accuracy is around 30 arcsec. That corresponds to 2
seconds of time error. Since I don't sync my scope, but rely on an accurate time
and pointing model, I depend on very accurate time measurement. Of course, if
you are working visually, and syncing you scope to calibrate the RA, than you
don't need much accuracy at all. For occultation timing, a second is a large
error.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #7  
Old August 14th 04, 08:18 PM
Carsten A. Arnholm
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John Beaderstadt wrote:
While reading in the bathroom on Sat, 14 Aug 2004 15:26:58 GMT, I saw
that "MikeThomas" had written:

For one thing, to do a polar alignment, you have to know your local
time
meridian offset and whether you
are east or west of it.


????????????

To do a polar alignment, I line up on the pole star. Time has nothing
to do with it,


Personally, I try to line up on the North Celestial Pole (since I live in
the northern hemisphere). While time affects the position of Polaris, it
does not affect the position of the North Celestial Pole (ignoring
precession). If you use Polaris as a polar alignment aid, you need to know
the time of day, unless your error tolerance is big enough.

although knowing how to put my 'scope in its "home"
position is critical.


That is not critical at all in my case, as I use drift alignment using a
german equatorial mount.

Clear skies
Carsten A. Arnholm
http://arnholm.org/
N59.776 E10.457

  #8  
Old August 14th 04, 11:51 PM
Davoud
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MikeThomas:
is completely dependent on timing. It is just easier if people report
observations of any kind in UTC. People should know what their local
offset is whether it is Daylight or standard, PDT, MST, MDT, EDT,
Europe, China or Antartica!!


So in what time zone(s) are the north and south poles located? Both
points are on every meridian and on no meridian.

For one thing, to do a polar alignment, you have to know your local time
meridian offset and whether you are east or west of it.


I drift-align my Questar without reference to any time at all. After
the alignment I need to know the R.A. of a star -- any visible star --
in order to move my R.A. setting circle to the correct position as a
reference for finding other objects of known R.A. But I still don't
need to know what time it is in Tuguegarao* or Shibam-Kawkaban**, or,
indeed, where on earth I am.

Davoud

* generally poor for deep sky, good for solar system
** great skies, but a dangerous place

--
usenet *at* davidillig dawt com
  #9  
Old August 15th 04, 01:51 AM
Phil Wheeler
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MikeThomas wrote:
People should know what their local offset is whether it is
Daylight or standard, PDT, MST, MDT,EDT,Europe, China or Antartica!!


Hmmm .. wonder what the offset is at the South Pole? g

  #10  
Old August 17th 04, 09:39 AM
John Beaderstadt
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While reading in the bathroom on Sat, 14 Aug 2004 21:18:47 +0200, I
saw that "Carsten A. Arnholm" had written:

If you use Polaris as a polar alignment aid, you need to know
the time of day, unless your error tolerance is big enough.


Which is the big advantage of a goto scope. For polar alignment, I
just need to be in the ballpark; then I do the "Easy" two-star
alignment and I'm set for the evening.



--------------
Beady's Corollary to Occam's Razor: "The likeliest explanation of any phenomenon is almost always the most boring one imaginable."


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