Why should you bring your Sextant outside an hour earlier than your intended shoot? - PowerPoint PPT Presentation

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Why should you bring your Sextant outside an hour earlier than your intended shoot?

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Why should you bring your Sextant outside an hour earlier than your intended shoot? Let it acclimatize to temperature. How should you NEVER pick your Sextant? – PowerPoint PPT presentation

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Title: Why should you bring your Sextant outside an hour earlier than your intended shoot?


1
Why should you bring your Sextant outside an hour
earlier than your intended shoot? Let it
acclimatize to temperature.
How should you NEVER pick your Sextant? By the
Index Arm.
What is the first thing you do after removing
your Sextant from the box? Put the lanyard over
your neck or wrist.
What are the Initial maintenance checks? Clean
mirrors, working batteries/bulbs, polished
Arc/Vernier.
What gear should you have with you? Watch,
pencil, paper/worksheet/notebook.
What should you know about your watch? How fast
or slow it is compared to UTC.
What is the first check of your Sextant? Index
Error.
How is Index Error calculated? Set Sextant to
zero and sight the horizon, adjust image until
you get unbroken line.
2
How do you correct Index Error? Adjust Index
Mirror and Horizon Glass to get as close to a
zero reading as possible.
What does Hs stand for? The observed height of
the body with the Sextant.
What if something is obstructing the direction
toward the body? You can shoot away from the
body IF the Altitude is high.
How is Index Error applied? If its on-its off,
If its off-its on. gtzero add, zerolt subtract.
Why do you swing the arc? To visually make
sure the body is truly resting on the horizon.
What is He and Dip? The observers Height of Eye
above the surface and the angle to the
actual/geographic horizon.
How do you move the Sextant when the body is
brought down to the horizon? Swing the arc.
Rock the Sextant so the body describes an arc.
What is The Altitude Correction? The correction
for refraction and parallax of light through the
atmosphere.
3
What does Ho stand for? The actual height of the
body observed with all corrections applied.
Where you extract Dip, Altitude Correction and
Temp/Press values? The front pages of the
Nautical Almanac.
What does Declination mean? The bodys angular
distance North or South of our Latitude compared
to the North Celestial Pole.
What does Altitude mean? The angular height of
the body above the Celestial Horizon.
What does GP mean? The bodys pinpoint
Geographical Position on the Earth.
What does Greenwich Hour Angle, GHA mean? The
angular distance of the body West from First
Point of Aries V through 360 degrees.
What is Sidereal Hour Angle, SHA? A Stars
angular distance West of First Point of Aries V.
What does Local Hour Angle, LHA mean? The
angular distance between the bodys Hour Angle
and our Longitude.
4
What is special about the Suns Declination? It
may increase or decrease, depending on the season.
What special correction does the Sun
have? Little d.
What special aspect of Declination do you need to
know? Whether its North or South.
What special corrections do the Moon and Planets
have? Little v and d.
What is the purpose of Assumed Latitude? To have
a Latitude in whole degrees for entering the
tables.
What is the Assumed Position, AP? The reference
position plotted on the chart from which the
direction and distance Lines of Position are
plotted.
What does Azimuth mean? The compass direction
towards the GP of the body.
What is Hc? The calculated altitude of the body
for plotting on the chart.
5
What is Z? The Azimuth angle of the GP.
Sunny day, Take Noon Position, Advance Two spaces!
Rain squalls, no fix today, Lose a turn.
What is Zn? The Azimuth from the Assumed
Position towards the GP for plotting on the chart.
Shoot the Moon, Advance one space!
How do you figure Altitude Intercept? If Ho is
more than Hc, then you are towards the GP.
What does it mean to plot Towards the GP? Plot
from your AP along the Zn Azimuth towards the GP.
Cloudy day, No fix, Subtract one from next roll.
6
Good Polaris sight, Advance one space!
Landfall, resupply, correct Chronometers, Advance
two spaces!
Pirates! Change course to Northwest!
Wind veers North, blown off course, Course change
to Northeast.
Rough seas, dead reckoning suspect, Lose a turn.
All Officers fix position accurately, Advance two
spaces!
Meet ship at sea, have a Gam, exchange Mail, Add
one to next roll!
Headwinds! Lose a turn.
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