Short Nerd Chief

Jason Kottke has a link to some sci-fi starship comparison charts, ranging from 10 pixels per meter to 100 meters per pixel.  The charts don’t include the Death Star, because it is “so friggin’ huge.”  Jason includes another link, however, which does include the Death Star and Death Star II.  This chart pegs the stations at 120 km and 160 km in diameter, respectively.  This seems really, really low.  Those are the offical LucasArts numbers, but some obsessive fans won’t accept it and have attempted to extrapolate the size based on things like Vader’s ship and the Equatorial Trench visible in the films:

The equatorial “waistband” trench of the Death Star II can be compared to the diameter of the whole battle station in photographs taken from astronomical distances. The local area around the docking bays used by the Emperor and Lord Vader can be measured approximately by scaling the shuttle with surrounding features. (The height of a landed shuttle is approximately 23m.) This local area appears to be somewhere inside the waistband trench; which enables us to calculate a lower limit on the size of the Death Star II.

A detailed image of the whole battle station appears in The Art of Star Wars: Episode VI. In this large scan, the polar diameter is 1682 pixels, the equatorial diameter is 1686 pixels and the height of the equatorial trench is 11 pixels (in the well illuminated region near the middle of the picture). That means that the diameter of the Death Star II is about 153±7 times the width of the waistband trench, whatever that may be.

The height of Lord Vader’s hangar can be determined from images taken during Luke’s escape. In this image the shuttle is about 85 pixels high (extrapolating the additional height of landing gear), and the bay aperture is about 244 pixels high. According to published blueprints, the shuttle is about 22.25m high, and therefore the hangar aperture is 64m high. (Similarly the width of the aperture is approximately 237/42 times the shuttle’s closed wingspan, according to this image taken when the shuttle was exactly at the entrance.)

Vader’s is the smallest hangar in the vicinity. The Emperor’s is 62/18 times higher. The bays are all set back into a rectangular notch, which itself is within a deep notch in the hull of the station. Neglecting the displacement of the hangars away from camera, this image shows that the inner and outer notches are respectively 260/18 and 501/18 times the height of Vader’s hangar, or approxoimately 0.92km and 1.8km.

The outer notch cannot be higher than the total height of the equatorial trench. If it were itself the equatorial trench then the entire battle station would have a diameter of about 270km. This is only a lower limit on the size of the Death Star II, because the outer notch is not necessarily the whole trench. Comparing this figure with the result from astrophysical considerations and Richard Edlund’s statement in CINEFEX, the outermost visible notch turns out to be a third of the height of the equatorial trench, or less. The top-left corner of one matte painting shows what may be part of the next higher level of notch. Therefore the most realistic picture is for a space station of over 800km diameter, with a ~5.3km equatorial trench containing ~1.8km high notches, within which there are deeper notches of 0.9km height, which contain hangars that are 64m high or less.

Or maybe you’d prefer astrophysics to space station architectural design:

The Endor moon needs to have a surface gravity strong enough for humans to move in comfort, and an escape velocity comparable to Earth’s in order to retain a breathable atmosphere [for detailed discussion, see Planets: Habitability]. The two extremes of viable solutions are:

• a low-density planet composed entirely of the lightest silicates with an extreme povery of metals, but with a radius substantially greater than Earth; or
• a globe with approximately Earth-like composition but a slightly smaller radius.

In the latter case, the Endor moon would be intermediate between Earth and Mars, but closest to the size of Earth. Assuming a bulk composition consistent with known terrestrial planets and a best estimate of 2/3 terrestrial surface gravity, the sanctuary moon’s average density would be about 4 - 5 g / cm³ implying a radius of roughly 5200 km (80% that of Earth). This is a very approximate value and might vary by hundreds of kilometres depending on the weighting of the particular assumptions. However this value serves as a strongly indicative lower limit because a light-element composition would imply a greater global radius, and a heavy-element composition is astronomically unattainable (and couldn’t shrink the diameter by much better than half). The moon’s radius could not conceivably be less than about four-thousand kilometres.

If there is nothing abnormal and artificial about the moon’s compostion then the diameter of the Death Star II is scaled to approximately

D = 900 ± 60 km

So I’m a nerd, but that’s just beyond the pale. It’s really friggin’ big.  But not as big as Halo.