SH4's rendering of Sun and Moon

[Rockin Robbins]

Over at subsowespac a question came up about a typical SH4 screenshot taken from the Alaska area, showing



Kim Ronhoff said the time was 1943 to 1944 and asked if the game was showing an eclipse and how accurate was SH4 anyway. I replied "lousy!" and someone else said "pretty darn close." That calls for a Mythbusters-like investigation. Well, here there are several things to check.

1. Was there a solar eclipse visible from Dutch Harbor in 1943 or 1944?
2. Was it a partial eclipse like that shown here?
3. What about the relative sizes of sun and moon?
4. What about the phase of the moon shown by SH4?
5. Did any solar eclipse happen at sunset?
6. If not, what were the relative positions of sun and moon on the sunset of a possible solar eclipse?

To #1, there were two solar eclipses seen from Dutch Harbor in 1943-1944. The first, 2/4/43 was a total eclipse (well, 99%, that's pretty close to total!) beginning at 13:56, at maximum 15:11 and ending 16:25 local time. The second was 1/25/1944 and the moon almost had a clean miss on the sun. No event was visible. SH4 shows a clear overlap, so the event of 2/4/43 is elected. The answer to #1 is yes, there was one and only one suitable solar eclipse in our time frame, on 2/4/43.

#2's answer is no. This eclipse was so nearly total that an observer might not have been able to tell that it wasn't. 99% of total is pretty darned close!

#3 is an easy one. At all times the angular size of the moon and sun are almost exactly the same: ½ degree in the sky. You can just cover them with the fingernail of your little finger at arm's length. The moon does vary a little in size, but that difference is not detectable to the eye, or even in a pair of binoculars. SH4 fails miserably there.

#4. SH4 shows about a one eighth phase moon there. Unfortunately, solar eclipses ALWAYS happen when the phase of the moon is exactly 180º, that is a perfect new moon with zero percent illumination from our point of view. Now the new moon is quite bright because of earthshine, secondary illumination from the full earth, but because of the skyglow from the sun, a new moon is invisible! There is simply nothing to see. The SH4 depiction in that respect is a sorry joke.

#5. Let's watch the solar eclipse of 2/4/43 from Dutch Harbor! As I said, the eclipse actually started at 3:11 pm local time, a long way from sunset. But can you spot the real surprise here? We'll be looking in a constant direction just east of south and the movement of sun and moon will be as it was on that day:



Can you see the gotcha? Yup, we're darned far north and the sun doesn't go up and down like we expect. In fact, it makes big circles around the sky at a shallow angle to the horizon and only travels a short distance below the horizon! This Dutch Harbor is one freaky place! Who gave the sun permission to act like that? So what the heck? Does the Sun set at all? Since the eclipse happens nothing like what SH4 showed, what really was the position of the Sun and Moon at sunset?

#6. Here is the position at sunset: 5:49 pm local time.



The sun and moon have traveled around half the sky, moving almost horizontally from left to right and dove at a shallow angle of about 10º from the horizon line to barely dip below the horizon for awhile tonight. They will never be more than about 20º below the horizon! You can barely see the moon lit by earthshine, 1º, that's two lunar or solar diameters away from the Sun, above and to the left, a long way from the SH4 plot. Notice that Sun and Moon are the same size and that no portion of the Moon is lit.

Conclusion: SH4 fails in all respects to properly render solar system objects. All speculation and claims of accurate celestial navigation by solar or lunar positions is pure unadulterated bunkum!

In the real sky no stars would be visible in either picture. They are only shown to make clear the relative motion of sky and earth's horizon. Also in the glare of the Sun the moon would not be seen at all, by naked eye or in any kind of optical instrument.

SH4's grade for this exercise? FAIL! FAIL! FAIL!