I think the error, if such it was, didn't come from converting their scratched diagram into a larger scale - it's quite conceivable that they were capable of doing that with virtually zero error. It would have come between looking up and drawing what they saw.

You'll like this, as it's practical. Get the alignment on screen, step back (more than 20 yards ideally so it appears of the size it appears in the sky) and repeatedly try to replicate it on paper.
My score, out of 5 attempts:
Worse than both - 3.
Better than the Egyptians - 2,
Better than Yorkshire - nil.

Ah but this doesn't rule out sheer chance. And round we go again.