Re: [Flightgear-devel] Sun Light placement
Hi All, Thanks for the astronomy lesson. I will try to not ask any more silly questions. Durk's explanation illustrated the point so well that even I could understand it. :0) Mind you, the information you have all given me means any Country Music or Cowboy films, which refer to the Sun setting in the West, will have to be seasonably adjusted in future. Coming back to my item 1 though: http://i.imgur.com/N9wDU.png As shown in this picture, I am facing 350º (almost due North), at 0915 hrs, but the light source is coming from the left (West). Now let's see if this one can be explained by my ignorance. Cheers, Vic-- Get a FREE DOWNLOAD! and learn more about uberSVN rich system, user administration capabilities and model configuration. Take the hassle out of deploying and managing Subversion and the tools developers use with it. http://p.sf.net/sfu/wandisco-d2d-2___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Sun Light placement
On Thursday 18 August 2011 11:36:46 Vic Marriott wrote: Hi All, I am not blaming this on the new V 2.4.0, because this problem existed before. I didn't want to distract anyone working on the new release. 1. I have noticed, that when at EGKA the light is showing from the wrong direction. This pic was taken at 0915 today: http://i.imgur.com/N9wDU.png 2. At dusk, the Sun shows at 290º. This can't be correct as EGKA is at 50.50º north. I would expect the Sun to be below 270º. http://i.imgur.com/cd9Ub.png Is this a known fault, or should I raise it on the bug tracker? Cheers, Vic According to heavens above, the 290 degrees azimuth for dusk is about right: http://www.heavens- above.com/sun.aspx?lat=50.81982lng=-0.14282loc=Unspecifiedalt=0tz=BST -- Get a FREE DOWNLOAD! and learn more about uberSVN rich system, user administration capabilities and model configuration. Take the hassle out of deploying and managing Subversion and the tools developers use with it. http://p.sf.net/sfu/wandisco-d2d-2 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Sun Light placement
On Thu, 2011-08-18 at 12:32 +0300, Emilian Huminiuc wrote: http://www.heavens- above.com/sun.aspx?lat=50.81982lng=-0.14282loc=Unspecifiedalt=0tz=BST Yeah it's probably not the sun position but rather the sky dome coloring code that's the problem. Erik -- Get a FREE DOWNLOAD! and learn more about uberSVN rich system, user administration capabilities and model configuration. Take the hassle out of deploying and managing Subversion and the tools developers use with it. http://p.sf.net/sfu/wandisco-d2d-2 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Sun Light placement
Hi Vic, On 18 Aug 2011, at 10:36, Vic Marriott wrote: 2. At dusk, the Sun shows at 290º. This can't be correct as EGKA is at 50.50º north. I would expect the Sun to be below 270º. http://i.imgur.com/cd9Ub.png The compass direction of the sunset's location is actually more related to the time of year then it is related to latitude. In Nothern hemisphere summer, the sun always sets north of the 270 degree line, while in wintertime it's south. The amount of deviation is related to how far north / south your are, which is in turn related to the amount of seasonal daylight time variation that occurs as a function of latitude. I currently don't have time for a lengthy explanation, but the 23 degree tilt of the earth's rotation axis with respect to the sun is of key importance here. When you go far enough north, the location of sunset will touch the 360 degree line on June 21; in other words the sun touches the horizon due north. That latitude is known as the arctic circle. If you go even further north, the sun will no longer set (in summer time), and keep moving all the way through the northern hemisphere, hence causing the midsummer night daylight. I'm happy to explain the process in more detail as soon as I have more time. Cheers, Durk -- Get a FREE DOWNLOAD! and learn more about uberSVN rich system, user administration capabilities and model configuration. Take the hassle out of deploying and managing Subversion and the tools developers use with it. http://p.sf.net/sfu/wandisco-d2d-2 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
