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Re: [skymap] UTC, Local time and Changes of Location

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  • Chris Marriott
    ... From: Ian & Janey Richards To: Sent: Saturday, September 01, 2001 4:36 AM Subject: [skymap] UTC, Local
    Message 1 of 4 , Sep 1, 2001
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      ----- Original Message -----
      From: Ian & Janey Richards <ijrichards@...>
      To: <skymap@yahoogroups.com>
      Sent: Saturday, September 01, 2001 4:36 AM
      Subject: [skymap] UTC, Local time and Changes of Location


      > It is very annoying when one changes the location on Earth, from say
      Sydney to London, that the current "map time" is changed - the local time is
      maintained and therefore the "map time" is adjusted to the local time in the
      new location. This seems to me to be counter-intuitive. Is there a way of
      fixing the "map time" in absolute time (ie. UTC) hen the location (and hence
      time zone) changes. Of course I could add "dummy" locations that all have a
      time zone aligned with UTC, but this is far from ideal. <<

      I'm afraid I must respectfully disagree with you. Drawing a map generally
      involves two separate operations - setting the location, and setting the
      time. As things currently stand, you can do this in either order - set the
      location and then set the time, or set the time and then set the location.
      If the program worked as you suggested, if the map's current location were,
      say, New York, and you wanted to draw a map for Sydney, you'd have to
      remember to first change the location to Sydney and then change the time to
      whatever the desired time was; if you did it the other way around, the
      program would change the time when you changed the location! That would make
      it VERY difficult to use!

      As long as you remember that SkyMap's time is always a LOCAL time, I really
      don't think there's any cause for confusion. If you want to work in UT, all
      you have to do is set the time zone to zero for your location.

      When drawing a map, it's local time which is normally of interest - you want
      to see what the sky looks like at 10pm in Sydney. What you're saying, if I
      understand you correctly, is that you want to draw a map showing the sky in
      Sydney as seen at 10pm somewhere else in the world - that seems very odd to
      me!

      > I also note that there is no way to show the current map time in UTC on
      the status bar - only local time (this is separate from the ability to
      display "current" LMT/UTC/LST which may bear no relationship to the "map
      time" and as such, I find potentially misleading.

      I'll certainly add that to the "to do" list; that would be a useful
      enhancement. Perhaps it's worth pointing out that you can obtain the current
      UT time from the "Help/Map Status" menu item.

      Regards,

      Chris
      ---------------------------------------------------------------
      Chris Marriott, SkyMap Software, UK
      e-mail: chris@... Web site: http://www.skymap.com
      Astronomy software written by astronomers, for astronomers
    • Ian & Janey Richards
      I guess in most circumstances/uses I would agree with what you say. I was specifically mentioning the case of observing an event from several locations, eg.
      Message 2 of 4 , Sep 1, 2001
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        I guess in most circumstances/uses I would agree with what you say. I was specifically mentioning the case of observing an "event" from several locations, eg. you go to an eclipse or transit from a table and a "go to" (time) command, then you want to change location and have the absolute time locked. It just seemed to me to be a nice option to add - a kind of "time lock". Maybe it's just me!

        Once again, Chris, thanks for your prompt response.

        Ian.

        ----------
        From: Chris Marriott[SMTP:chris@...]
        Sent: Saturday, 1 September 2001 18:34
        To: skymap@yahoogroups.com
        Subject: Re: [skymap] UTC, Local time and Changes of Location


        ----- Original Message -----
        From: Ian & Janey Richards <ijrichards@...>
        To: <skymap@yahoogroups.com>
        Sent: Saturday, September 01, 2001 4:36 AM
        Subject: [skymap] UTC, Local time and Changes of Location


        > It is very annoying when one changes the location on Earth, from say
        Sydney to London, that the current "map time" is changed - the local time is
        maintained and therefore the "map time" is adjusted to the local time in the
        new location. This seems to me to be counter-intuitive. Is there a way of
        fixing the "map time" in absolute time (ie. UTC) hen the location (and hence
        time zone) changes. Of course I could add "dummy" locations that all have a
        time zone aligned with UTC, but this is far from ideal. <<

        I'm afraid I must respectfully disagree with you. Drawing a map generally
        involves two separate operations - setting the location, and setting the
        time. As things currently stand, you can do this in either order - set the
        location and then set the time, or set the time and then set the location.
        If the program worked as you suggested, if the map's current location were,
        say, New York, and you wanted to draw a map for Sydney, you'd have to
        remember to first change the location to Sydney and then change the time to
        whatever the desired time was; if you did it the other way around, the
        program would change the time when you changed the location! That would make
        it VERY difficult to use!

        As long as you remember that SkyMap's time is always a LOCAL time, I really
        don't think there's any cause for confusion. If you want to work in UT, all
        you have to do is set the time zone to zero for your location.

        When drawing a map, it's local time which is normally of interest - you want
        to see what the sky looks like at 10pm in Sydney. What you're saying, if I
        understand you correctly, is that you want to draw a map showing the sky in
        Sydney as seen at 10pm somewhere else in the world - that seems very odd to
        me!

        > I also note that there is no way to show the current map time in UTC on
        the status bar - only local time (this is separate from the ability to
        display "current" LMT/UTC/LST which may bear no relationship to the "map
        time" and as such, I find potentially misleading.

        I'll certainly add that to the "to do" list; that would be a useful
        enhancement. Perhaps it's worth pointing out that you can obtain the current
        UT time from the "Help/Map Status" menu item.

        Regards,

        Chris
        ---------------------------------------------------------------
        Chris Marriott, SkyMap Software, UK
        e-mail: chris@... Web site: http://www.skymap.com
        Astronomy software written by astronomers, for astronomers




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      • Chris Marriott
        ... From: Ian & Janey Richards To: Sent: Sunday, September 02, 2001 4:00 AM Subject: RE: [skymap] UTC, Local
        Message 3 of 4 , Sep 2, 2001
        • 0 Attachment
          ----- Original Message -----
          From: Ian & Janey Richards <ijrichards@...>
          To: <skymap@yahoogroups.com>
          Sent: Sunday, September 02, 2001 4:00 AM
          Subject: RE: [skymap] UTC, Local time and Changes of Location


          > I guess in most circumstances/uses I would agree with what you say. I was
          specifically mentioning the case of observing an "event" from several
          locations, eg. you go to an eclipse or transit from a table and a "go to"
          (time) command, then you want to change location and have the absolute time
          locked. It just seemed to me to be a nice option to add - a kind of "time
          lock". Maybe it's just me!<<

          I certainly note what you say, and I'll add it to the "to do" list. In the
          mean time, the way to do this is to work in UT by setting the time zone of
          your location to zero.

          Regards,

          Chris
          ---------------------------------------------------------------
          Chris Marriott, SkyMap Software, UK
          e-mail: chris@... Web site: http://www.skymap.com
          Astronomy software written by astronomers, for astronomers
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