Sunrise/sunset

[Admin]

Peter, good page graphically.

 

You could also use the weather page on the forums here and just insert the airfield name or its ID or any lat/long and click the button. The first light and last light is shown as per Airservices calculations

 

 

[Guest Marius Grobler]

Hi Guys,a long time ago I wrote a program to calculate and help visualise first/last light and sun rise/set for any location on Earth.

 

If you're interested, have a look at

 

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[/url]http://planofile.com/Earth.html

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-Peter

 

 

 

Beautiful! Thanks

 

 

 

Marius

 

 

 

 

 

 

[facthunter]

Last light, end of daylight.etc.

 

TC123, No I haven't done manny's course.

 

The thing to do with the situation is what you must, but it should be done before you run out of options. Most bad outcomes are not the result of a single misjudgement, but an accumulation of a number of factors in combination.

 

As you are aware, there is practically No twilight in the tropics, and nobody can really land straight into the setting (or rising) sun, so particularly in the late afternoon, you can anticipate the possibility of both problems arising,( the glare and/or the sudden darkness), IF you are likely to HAVE to land towards the west, late in the day.

 

When the sun is a few degrees above the horizon, you can use your cap (or visor) to screen the sun out, but sometimes this does not work.

 

IF there is a PAL system, or someone can put out a row of lights, you are laughing, but RAAus is not operating in this environment, and you are therefore not trained for it, so if there are cattle on the strip then the road would have to be it, when you can still see what you are doing. Beware the almost inevitable powerlines.

 

I wanted to make the point that the landing light(s), don't help a lot, especially if they illuminate the back of the prop. Nev...

 

 

[Guest pelorus32]

The three definitions that are relevant here are:

 

• Civil Twilight: The centre of the refracted disc of the sun is 6 degrees below the horizon;
   
   
  
• Nautical Twilight: The centre of the refracted disc of the sun is 12 degrees below the horizon; and
   
   
  
• Astronomical Twilight: The centre of the refracted disc of the sun is 18 degrees below the horizon.
   
   
  

 

 

As the rotational speed of the earth averages 15 degrees per hour or 4 minutes for a degree the relevant times are 24 minutes, 48 minutes and 72 minutes after the refracted centre of the disc of the sun passes the horizon. Which is not what we would ordinarily call sunset. Sunset is the time that the trailing limb of the sun dips below the horizon. Because of refraction the sun appears to be lifted about half a degree so sunset is about 2 minutes later than the astronomical position of the sun would suggest. (A limb is the upper or lower edge of an astronomical body.) In celestial navigation when taking moon sights sometimes only one limb is available. In any event for all sights you shoot one limb or other and then correct for semi-diameter using a value from the tables as you can't determine what the centre of the body is.

 

Just for another bit of trivia the correction for semi-diameter and parallax (yes even at that distance) for the sun is between 15.5 and 16.5 minutes or around 25% of a degree making a difference of about 1 minute.

 

Our "last light" is I think based on civil twilight. But that really is all just completely theoretical because of clouds, dust, hills....give yourself plenty of time.

 

Hope you don't mind the trivia

 

Regards

 

Mike

 

 

[Admin]

- Geez ya good Mike

 

 

[Guest pelorus32]

- Geez ya good Mike

I will report your view to my wife - she needs reminding

 

Regards

 

Mike