Loading ...
Sorry, an error occurred while loading the content.

Re: [skymap] Re: Archeological study

Expand Messages
  • Chris Marriott
    ... From: Mark Crossley To: Sent: Saturday, January 31, 2009 11:04 PM Subject: Re: [skymap] Re:
    Message 1 of 14 , Feb 1, 2009
    • 0 Attachment
      ----- Original Message -----
      From: "Mark Crossley" <public@...>
      To: <skymap@yahoogroups.com>
      Sent: Saturday, January 31, 2009 11:04 PM
      Subject: Re: [skymap] Re: Archeological study


      > Simon
      >
      > It doesn't make ANY difference to the star displays, I thought Chris had
      > already responded to this. The Altitude is only used for 'near Earth'
      > calculations - satellites, local eclipse circumstances? and possibly the
      > Moon?

      It's used for a few things - the calculation of refraction, and (as you say)
      satellite positions and circumstances of local eclipses amongst others. It
      is NOT used to compute the "depression of the horizon" - astronomers ALWAYS
      measure altitude from a theoretical "sea" horizon.
    • Mark Crossley
      Chris Whilst SMP quite properly should always calculate the altitude of objects from the theoretical horizon, I can see for some people that [optionally]
      Message 2 of 14 , Feb 1, 2009
      • 0 Attachment
        Chris

        Whilst SMP quite properly should always calculate the altitude of objects
        from the theoretical horizon, I can see for some people that [optionally]
        displaying the horizon line in its 'depressed' position could be useful. I
        say optionally because elevation only affects the horizon if you are
        elevated relative to the surrounding land, which most of us are if only by 6
        feet!

        Maybe one for SMP 13!

        Mark

        2009/2/1 Chris Marriott <chris@...>

        >
        > ----- Original Message -----
        > From: "Mark Crossley" <public@...<public%40wilmslowastro.com>
        > >
        > To: <skymap@yahoogroups.com <skymap%40yahoogroups.com>>
        > Sent: Saturday, January 31, 2009 11:04 PM
        > Subject: Re: [skymap] Re: Archeological study
        >
        > > Simon
        > >
        > > It doesn't make ANY difference to the star displays, I thought Chris had
        > > already responded to this. The Altitude is only used for 'near Earth'
        > > calculations - satellites, local eclipse circumstances? and possibly the
        > > Moon?
        >
        > It's used for a few things - the calculation of refraction, and (as you
        > say)
        > satellite positions and circumstances of local eclipses amongst others. It
        > is NOT used to compute the "depression of the horizon" - astronomers ALWAYS
        >
        > measure altitude from a theoretical "sea" horizon.
        >
        >
        >


        [Non-text portions of this message have been removed]
      • KevinDCornwell
        Chris - I observe at 9200ft, sometimes at 14,000ft. My horizon is the pacific ocean. Is there a way for SMP to show me the visual horizon related to my
        Message 3 of 14 , Nov 1, 2009
        • 0 Attachment
          Chris - I observe at 9200ft, sometimes at 14,000ft. My horizon is the pacific ocean. Is there a way for SMP to show me the visual horizon related to my altitude? Or, is the difference so small that I couldn't tell the difference anyway. I'm hoping to get maybe 2 more degrees when I get to 14,000...

          Thanks,
          Kevin
          Kevin Cornwell
          observing from Mauna Kea, Hawaii.

          --- In skymap@yahoogroups.com, Mark Crossley <public@...> wrote:
          >
          > Chris
          >
          > Whilst SMP quite properly should always calculate the altitude of objects
          > from the theoretical horizon, I can see for some people that [optionally]
          > displaying the horizon line in its 'depressed' position could be useful. I
          > say optionally because elevation only affects the horizon if you are
          > elevated relative to the surrounding land, which most of us are if only by 6
          > feet!
          >
          > Maybe one for SMP 13!
          >
          > Mark
          >
          > 2009/2/1 Chris Marriott <chris@...>
          >
          > >
          > > ----- Original Message -----
          > > From: "Mark Crossley" <public@...<public%40wilmslowastro.com>
          > > >
          > > To: <skymap@yahoogroups.com <skymap%40yahoogroups.com>>
          > > Sent: Saturday, January 31, 2009 11:04 PM
          > > Subject: Re: [skymap] Re: Archeological study
          > >
          > > > Simon
          > > >
          > > > It doesn't make ANY difference to the star displays, I thought Chris had
          > > > already responded to this. The Altitude is only used for 'near Earth'
          > > > calculations - satellites, local eclipse circumstances? and possibly the
          > > > Moon?
          > >
          > > It's used for a few things - the calculation of refraction, and (as you
          > > say)
          > > satellite positions and circumstances of local eclipses amongst others. It
          > > is NOT used to compute the "depression of the horizon" - astronomers ALWAYS
          > >
          > > measure altitude from a theoretical "sea" horizon.
          > >
          > >
          > >
          >
          >
          > [Non-text portions of this message have been removed]
          >
        • chris@chrism.demon.co.uk
          ... I m afraid that s not a facility offered by the program. Sorry. Regards, Chris
          Message 4 of 14 , Nov 1, 2009
          • 0 Attachment
            Quoting KevinDCornwell <kevindcornwell@...>:

            > Chris - I observe at 9200ft, sometimes at 14,000ft. My horizon is
            > the pacific ocean. Is there a way for SMP to show me the visual
            > horizon related to my altitude? Or, is the difference so small that
            > I couldn't tell the difference anyway. I'm hoping to get maybe 2
            > more degrees when I get to 14,000...
            >

            I'm afraid that's not a facility offered by the program. Sorry.

            Regards,

            Chris
          • Nigel Tasker
            With a little calculation, you could move your SMP location towards your view direction, to take account of your height of eye . This link tells you all about
            Message 5 of 14 , Nov 2, 2009
            • 0 Attachment
              With a little calculation, you could move your SMP location towards your view direction, to take account of your "height of eye".

              This link tells you all about it:

              http://mintaka.sdsu.edu/GF/explain/atmos_refr/dip.html

              Nigel Tasker
              ----- Original Message -----
              From: KevinDCornwell
              To: skymap@yahoogroups.com
              Sent: Monday, November 02, 2009 4:47 AM
              Subject: [skymap] Re: Archeological study


              Chris - I observe at 9200ft, sometimes at 14,000ft. My horizon is the pacific ocean. Is there a way for SMP to show me the visual horizon related to my altitude? Or, is the difference so small that I couldn't tell the difference anyway. I'm hoping to get maybe 2 more degrees when I get to 14,000...

              Thanks,
              Kevin
              Kevin Cornwell
              observing from Mauna Kea, Hawaii.

              --- In skymap@yahoogroups.com, Mark Crossley <public@...> wrote:
              >
              > Chris
              >
              > Whilst SMP quite properly should always calculate the altitude of objects
              > from the theoretical horizon, I can see for some people that [optionally]
              > displaying the horizon line in its 'depressed' position could be useful. I
              > say optionally because elevation only affects the horizon if you are
              > elevated relative to the surrounding land, which most of us are if only by 6
              > feet!
              >
              > Maybe one for SMP 13!
              >
              > Mark
              >
              > 2009/2/1 Chris Marriott <chris@...>
              >
              > >
              > > ----- Original Message -----
              > > From: "Mark Crossley" <public@...<public%40wilmslowastro.com>
              > > >
              > > To: <skymap@yahoogroups.com <skymap%40yahoogroups.com>>
              > > Sent: Saturday, January 31, 2009 11:04 PM
              > > Subject: Re: [skymap] Re: Archeological study
              > >
              > > > Simon
              > > >
              > > > It doesn't make ANY difference to the star displays, I thought Chris had
              > > > already responded to this. The Altitude is only used for 'near Earth'
              > > > calculations - satellites, local eclipse circumstances? and possibly the
              > > > Moon?
              > >
              > > It's used for a few things - the calculation of refraction, and (as you
              > > say)
              > > satellite positions and circumstances of local eclipses amongst others. It
              > > is NOT used to compute the "depression of the horizon" - astronomers ALWAYS
              > >
              > > measure altitude from a theoretical "sea" horizon.
              > >
              > >
              > >
              >
              >
              > [Non-text portions of this message have been removed]
              >




              ------------------------------------

              Yahoo! Groups Links




              --
              I am using the free version of SPAMfighter.
              We are a community of 6 million users fighting spam.
              SPAMfighter has removed 5419 of my spam emails to date.
              Get the free SPAMfighter here: http://www.spamfighter.com/len

              The Professional version does not have this message


              [Non-text portions of this message have been removed]
            • Chris Marriott
              ... From: Nigel Tasker To: Sent: Monday, November 02, 2009 4:38 PM Subject: Re: [skymap] Re: Archeological
              Message 6 of 14 , Nov 2, 2009
              • 0 Attachment
                ----- Original Message -----
                From: "Nigel Tasker" <nigeltasker@...>
                To: <skymap@yahoogroups.com>
                Sent: Monday, November 02, 2009 4:38 PM
                Subject: Re: [skymap] Re: Archeological study


                > With a little calculation, you could move your SMP location towards your
                > view direction, to take account of your "height of eye".
                >
                > This link tells you all about it:
                >
                > http://mintaka.sdsu.edu/GF/explain/atmos_refr/dip.html
                >
                > Nigel Tasker

                All that the dip of the horizon does is to "lower" the horizon below the
                horizontal, so, once you've calculated the amount, you could represent it on
                SkyMap by a user-defined horizon line below the normal horizon.

                Regards,

                Chris
              • Wm. Schwittek
                Kevin, If I ve done the math correctly, the angle of the horizon (assume the Earth is 4000 miles in radius) is: arcsin(4000/(4000+h)) where h is your height
                Message 7 of 14 , Nov 3, 2009
                • 0 Attachment
                  Kevin,

                  If I've done the math correctly, the angle of the horizon (assume the
                  Earth is 4000 miles in radius) is:

                  arcsin(4000/(4000+h))

                  where h is your height above sea level in miles. So, if you were 3
                  miles up (about 15,000 ft) your horizon would be out there at 87.78
                  degrees or about 2 degrees lower than it would be at sea level (which
                  would be 90 degrees).

                  - Bill



                  Re: Archeological study
                  Posted by: "KevinDCornwell" kevindcornwell@... kevindcornwell
                  Sun Nov 1, 2009 8:47 pm (PST)


                  Chris - I observe at 9200ft, sometimes at 14,000ft. My horizon is the
                  pacific ocean. Is there a way for SMP to show me the visual horizon
                  related to my altitude? Or, is the difference so small that I couldn't
                  tell the difference anyway. I'm hoping to get maybe 2 more degrees when
                  I get to 14,000...

                  Thanks,
                  Kevin
                  Kevin Cornwell
                  observing from Mauna Kea, Hawaii.
                Your message has been successfully submitted and would be delivered to recipients shortly.