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# Ilan Papini's VIRTUAL SAILOR 7

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27 Pages
English

Description

Frank Sarfati - 071006

Ilan Papini’s

TUTORIAL

USING THE VIRTUAL SEXTANT WITH VS7

By

Frankie the Funky Sailor
Frankie_the_funky_sailor@yahoo.co.uk

1. Introduction

1.1 Purpose of this tutorial: The purpose of this tutorial is to give some information about using
the virtual sextant (the “Virtual Sextant”) designed by Ilan Papini for his Virtual Sailor 7 (“VS7”),
and how to use the information obtained with the Virtual Sextant.

This tutorial will endeavour to be practical. The theory of celestial navigation and sextants will
not be dealt with here. I will write a more exhaustive and comprehensive tutorial on that subject
later.

1.2 why use a sextant: It may sound weird nowadays with GPS’ and satnav to want to learn how
to use a sextant. The reason is very simple: the system can breakdown, there’s no power or a
nasty wave floods the electric system. What do you do in such a case? If you can’t determine
your position, you have a problem, and probably a big one. So, although Virtual Sextant will not
teach how to use, in practice, a sextant, it may help and facilitate the learning process with an
actual sextant!!!

1.3 how does it work: the Virtual Sextant and any actual sextant work according to the same
principle: it measures the elevation of sun (or any other celestial body) above the horizon,
such an elevation being expressed in degrees.
Frank Sarfati - 071006

Practically speaking, Virtual ...

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Frank Sarfati - 071006
Ilan Papini s  VIRTUAL SAILOR 7©    TUTORIAL  USING THE VIRTUAL SEXTANT WITH VS7  By  Frankie the Funky Sailor Frankie_the_funky_sailor@yahoo.co.uk  1. Introduction  1.1 Purpose of this tutorial:The purpose of this tutorial is to give some information about using the virtual sextant (the “Virtual Sextant) designed by Ilan Papini for his Virtual Sailor 7 (“VS7), and how to use the information obtained with the Virtual Sextant.   This tutorial will endeavour to be practical. The theory of celestial navigation and sextants will not be dealt with here. I will write a more exhaustive and comprehensive tutorial on that subject later.  1.2 why use a sextant:It may sound weird nowadays with GPS’ and satnav to want to learn how to use a sextant. The reason is very simple: the system can breakdown, there’s no power or a nasty wave floods the electric system. What do you do in such a case? If you can’t determine your position, you have a problem, and probably a big one. So, although Virtual Sextant will not teach how to use, in practice, a sextant, it may help and facilitate the learning process with an actual sextant!!!   1.3 how does it work: Virtual Sextant and any actual  thesextant work according to the same principle: it measures the elevation of sun (or any other celestial body) above the horizon, such an elevation bein ex ressed in de rees.

Frank Sarfati - 071006    Practically speaking, Virtual Sextant and an actual sextant will “bring the sun down to the horizon. If you take a good note of the time at which you measure that angle (also call the “elevation), you can derive extremely useful information about where you are at a certain time.  1.4 Notice: Users of the Virtual sextant and readers of this tutorial should bear in mind the following:  (a) this tutorial will only deal with virtual sightings of the sun in VS7; other celestial bodies such as the stars, planets or the Moon will not be dealt with: it is much more complicated; it’s also customary to begin with the sun, which is a lot simpler to use in celestial navigation;  (b) learning how to use the Virtual Sextant may facilitate learning celestial navigation or at least some of its theoretical aspects.should not go at sea on the basisHowever, one of the information contained or derived from this tutorial, but should satisfy him/herself that he/she has sufficient, proper and adequate training, instrumentation and equipment before and when going at sea, all in accordance with applicable laws and regulations;  (c) I am in no way an expert in this area and everything I know, I have learned it by myself, through my readings and personal experience (e.g. spending hours on the beach training and people looking at me thinking “what a weirdo: is he that lost to use a sextant ON a beach ???). Theer fore, there may be some mistakes or inaccuracies or my approach may be unconventional. Please feel free to comment, criticise, discuss etcby contacting me atc..okuoohay@rolias_yknfue_the_kianfr. Or by putting your questions on any good VS fori (once you get the authorisation og the webmaster !!!); let me know by e-mail and I’ll have look and try to answer. Structure of the tutorial: So without further ado, let’s see, with a Virtual Sextant, what one can do!!!! The tutorial will be divided in two main sections:  do I use Virtual Sextant (section 2); How   How do I use the information obtained with Virtual Sextant (section 3).
1.5
Frank Sarfati - 071006

Frank Sarfati - 071006 2. How do I use Virtual Sextant?   2.1

Description of the Virtual Sextant

Screenshot 1  Most of you are familiar with Ilan’s VS7. You can see that there is a new icon: it represents a sextant. Double click on it or press shift + T.  Some of the Virtual Sextant’s functions are similar to those of the Telescope: Most of you are also familiar with the presentation below (see Screenshot 2): the Virtual Sextant window is very similar, at least in terms of presentation, to the virtual telescope. It has similar functions:   Azimut indicator: on top you can see the Azimut indicator: you operate it exactly as you do with the virtual telescope: right click and drag. You can also use the keypad (just like for the telescope function);  Zoom: on the right hand side, you can see the zoom function. Again, this works exactly as the zoom of the telescope function;  Vertical angle: You can also vary the vertical angle by right clicking and dragging the mouse (without clicking on any other functions) These are the only similarities. The differences are huge because a sextant is designed to measure the elevation of a celestial body over the horizon.

Frank Sarfati - 071006
Screenshot 2
Other functions are very different :  Elevation Knob:  This knob is used to bring the sun down to the horizon. In section 2.2, Ill explain how to do this.  As you turn the knob (and consequently “bringthe sun down to the horizon), the window called “elevation showsthe elevation of the sun (or whatever celestial body you may be sighting).  Elevation is measured in degrees, minutes of arc and seconds of arc. Here the elevation is also indicated in degrees and decimal degrees. We’ll see later on that this will avoid stupid (and fatal) errors.  Filter:  The filter is also a very important function of the sextant. On an actual sextant, the filter is used to protect your eye when sighting the sun and to reduce the glare: in order to do a proper sighting of the sun, you must see a perfectly neat circular disk and its edges without any glare.  Digital Watch:  Last but not least, the digital watch. You always have to note precisely, by the second, the time at which you do your sighting: one second of time can make a material difference in your result. Be precise !!!

Frank Sarfati - 071006 It is extremely important to note the Greenwich Mean Time (“GMT) when you do your sighting: in celestial navigation, you must never take note of the time in the time zone you are but only according to GMT. In future tutorials, we’ll see how we can determine local time with a sextant, but for know just think “GMT !!!!  GMT is given in hours, minutes and seconds and also in decimal. This will avoid a number of silly but fatal mistakes.  2.2 Using the Virtual Sextant  2.2.1 Step One  Click on the Virtual SextantIcon  (See Screenshot 1 above and 3 below).   Set the time and date at approximately 9:00 a.m. or 15 p.m. (around March or September of any given year, say 2006). For the first time, set the weather with 100% visibility, no clouds, no waves, no wind.   This will be explained in more detail in the next tutorial. All you need to know at this stage is that you don’t want the sun to be too high or too low for your first virtual sighting of the sun.

Screenshot 3

Frank Sarfati - 071006 2.2.2 Step Two  Turn the filter knob and set it to 60/65% approx - See Screenshot 4.

Screenshot4

Frank Sarfati - 071006     2.2.3

Step Three  Set the zoom to 3 and turn the elevation knob to approximately 30 degrees (30 in this example only, depending on your position and time) - See Screenshot 5.
Screenshot 5

Frank Sarfati - 071006  2.2.4 Step Four  use the keypad (4 or 6) or right click and slowly “turn the Virtual Sextant visor until you see the sun appear - See Screenshot 6.   In the (virtual) morning, you should look towards E or ESE (approx 120/130), in the (virtual) afternoon, WSW (approx 220/230). You should see the sun near the horizon slightly above (if in the morning) or below (if in the afternoon), “in the sea.

Screenshot 6

Frank Sarfati 071006 -  2.2.5 Step Five  centre the cross of the Virtual Sextant on the sun so the horizontal red line coincides with the horizon; set the horizontal angle to zero  See Screenshot 7

Screenshot 7

The sun’s lower limb should be like “one hair (i)below the horizon, if you’re sighting in the virtual morning (don’t forget, in the morning, the sun is going up towards the zenith); or (ii) above horizon if you’re sighting in the afternoon (when it’s going towards the nadir).
Frank Sarfati - 071006   2.2.6 Step Six  tangent the sun on the horizon  see Screenshot 8
Screenshot 8  Right click and move the sextant  in this arc like motion from left to right, not too fast and have your finger of your free hand ready to press F10.  press F10 as soon as the lower limb perfectly tangent the horizon.   On a piece of paper take a note of the elevation in both degrees and decimal and the time of the sighting (IN GMT !!!!) in hours and decimals.   Here, the elevation is 35:50:32 at 15:47:00 Hours GMT; in decimals, 35.8424 and 15,7857 Hours GMT.   (you may find a slightly different result than me, that’s because I wrote the tutorial over several days and I couldn’t remember which day I referred to initially)  2.3 Making it “more real   Once you have a little practice, you can set things in a more real mode:  Increase the wave height;   lock the simulation with F10 when you do you’re sighting; Don’t  Keep on sailing, don’t dock or anchor the ship;  a real watch (just make sure it’s set exactly on the same time as the clock of the Use Virtual Sextant i.e. GMT of Virtual Sextant)