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Ellen's Impact Diary Day 1 2 3

Day Three

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 already inserted!

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!

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Ellen's candles
Scientists Diaries

All craters great and small - read the other team members' diaries as they attempt to measure the impact of impacts: