Hi, I’m a recent backer, I really like the concept for the game and I’m a big fan of ‘realism’ in games. I’ve been playing with the Alpha build and I’m extremely impressed with the way the engine looks so far.
I hope I’m not out of line for immediately making suggestions and pointing out perceived issues with aspects of the production so far, in fact I rather hope that is the point of being an Alpha backer.
I have a passing interest in astronomy and I am often interested in how developers try to represent the sky in video games. As one of the selling points for this game is the realism, I hope that the developers are intending to increase the level of realism as far as the sky goes.
I am aware that the things I am going to point out do not interest everyone and a lot of people would not notice or care, but for me, a lot of these issues are actually quite jarring and definitely hurt the immersion. As well as that, I think that these things are extremely easy to correct as the mathematics around astronomy are well understood and plenty of games already handle these very well.
So, in my examination of the sky so far, I have looked at three objects:
The Sun
The Moon
The Stars
******************** THE SUN ********************
The Sun: This currently follows a fairly basic pattern. It rises directly East at 06:00 and sets directly West at 18:00. This isn’t so bad, in fact that happens on two days every year: 20th March and 22nd September, the equinoxes. On the equinox, it is easy to measure the latitude of your location using the maximum altitude of the Sun at midday.
This isn’t tremendously easy to do, but I think I managed a pretty good estimate and I put it at 62 degrees altitude due South at midday. This places us at a latitude of 38 degrees which is inaccurate. Bohemia has a latitude of about 50 degrees so the Sun should only reach 40 degrees at midday on the equinox. The current height would give us a much more mediterranean climate, equivalent to Athens or the south of Spain.
The Sun would reach this kind of altitude in Bohemia in the height of summer. But then it would be in the sky for nearly 16.5 hours, rising before 04:00 in a direction close to NE and setting after 20:00 in a direction close to NW
I measured the Sun’s angular diameter at roughly 1 degree, which is not too bad. The Sun in our sky has an angular diameter of about 0.5 degrees. I can see why you might want to increase this slightly for dramatic reasons.
******************** THE MOON ********************
The Moon: This fares much worse in my estimation and I do hope that changes will be made. For a start, it remain completely static in the sky and is only visible at night. The idea that the moon is only visible at night is nonsense, but strangely pervasive. Many children’s books perpetuate the idea which probably adds to the problem. It is obviously more noticeable at night, but we have all seen the Moon during the day and not thought it strange.
The Moon also has a large problem with its orientation. The lit side of the Moon is obviously illuminated by the Sun, therefore after sundown, the lit side should be pointing down, below the horizon. When the Moon appears, the lit side is actually pointing upwards which is completely impossible at night. This fact in itself I find much more jarring even than it remaining in a static position
It appears at an altitude of 45 degrees in the West immediately after sunset, this would be acceptable, but it should really then set in the West shortly after and it should appear as a downward facing cresent due to its relative position to the Sun.
I have measured the angular diameter at over 4 degrees (about 4.3). This is far too large. The Moons angular diameter is extremely similar to the Sun’s at about 0.5 degrees. This is what allows such beautiful solar eclipses.
******************** THE STARS ********************
The Stars: There are two main issues here, the stars are completely static in the sky, and they are arranged with Polaris at the zenith, an arrangement you would only see at the north pole.
It is the static placement that I find the most jarring. We all know that the Sun does not orbit the Earth and we only see it cross the sky every day because the planet rotates. If you watch a time lapse of the sun setting, as soon as the stars appear, you see stars setting in the West at exactly the same speed as the Sun did set. In fact everything in the sky moves at pretty much the same speed as the sun and in the same direction, because the discernable movement is actually caused by the rotation of the planet.
******************** THE FIX ********************
The corrections: I feel that these issues are reasonably easy to tackle. The games developer Bohemia Interactive actually already has an extremely accurate sky in a number of their titles: Operation Flashpoint, The Arma series and DayZ to name a few.
The mathematics around accurate astronomy are well understood and there are lots of free astronomy software packages available. However, a completely accurate model is not required. I would consider lowering the Sun, having Polaris at the correct altitude, having the star field rotate around Polaris and having the Moon also move with the star field with a phase and orientation that made sense as the minimum for an immersive experience.
TLDR: Please make the Stars and the Moon move across the sky like the Sun does! 
It might well just be me, but these seem like simple things to fix. Does anyone else feel that these issues hurt immersion?
