[jerf]

skykooler's point is that the Sun is not a point source. I think you may be mentally modeling it as a point source. A point source would make it just a matter of length, but when it's not a point source you can't help but get overlap between two "points" that are close enough together, because they both will be lit up at the same time, no matter how long the tube may be.

[Eridrus]

Ah, I think you're right.

Though the intensity would fade as the sun moves, so maybe you could potentially have some sort of intensity filter?

[grandalf]

Perhaps a nighttime version intended to work with starlight would work. It could be aimed at Polaris and combine the light from all the stars swirling around it to project the digits.