We couldn’t figure out where to put the hairline
to measure off it. Jonathan wanted to drill through
it. I took one of the eye pieces a part and then couldn’t
get it back together properly. The focal length is in
millimetres—the cameraman figured this out for
us. Then we got the hairline in the right place—if
you ever do this, buy an eyepiece with a reference line
Jonathan worked on increasing the stability of the
mount and added a bit to make the telescope move more
slowly and smoothly.
We took nine measure of the moon moving across the
reference line. It was a little shaky, but with practice,
we got used to it. When we repeated the measure, they
were really close. Jonathan had the stopwatch. I called
out when the moon started to cross the reference point
and when it stopped crossing. Then Jonathan and I switched
jobs—we got very similar results—whew!
Archimedes was a bit tougher as it is much smaller
than the moon. We doubled the magnification and measured
it passing the reference line in between gusts of wind.
So many nights are still here, but not tonight! Our
20 measures ranged between 2.95 and 3.89 seconds. Most
measures hovered at 3.2 seconds.
What was equally amazing is that the candles really
worked well, a beautiful orangey glow.
Our final estimate of Archimedes’s diameter was
72 km, plus or minus 10 km. The actual diameter is 82
km. That’s pretty good!
A note about astronomy: I’ve loved looking at
the stars all my life. I’ve even gotten a kick
out of mapping the path of the moon and the sun across
the sky. But none of this came very easily to me, at
least not explaining what was going on. I kept trying
and observing. Finally, I took a course in which we
had to act out what was going on in the sky. My head
spun; it was so much to take it. But I got it. Try it!