I did promise to post this a while back.... here it is finally.
The attached ZIP contains the Photoshop plugin from Panorama Tools which I use to adjust my moon image map for different positions in the sky. The PDF contains a brief set of instructions.
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The moons here are position around 180° heading, elevation 30°. Without adjusting the image map you end up looking at the far side of the moon, which is completely unrecognisable (left moon). You can use an offset filter to "rotate" the moon horizontally (centre moon, offset= (heading/360) x image width) but this can still look odd at higher elevations. Using Panroama Tools you can remap the image in one step, correcting the yaw, pitch and roll of the image texture to produce an accurate rendition.