Illumination geometry help

[gmike]

My daughter is working on the following procedure for measuring impact crater depth on Mercury:
https://www.sciencebuddies.org/science- ... #procedure

She followed the procedure and ended up with some depths that are a negative number and some that are a positive number. The negative appears at the point where she calculates the tangent. I observed her making the measurements all over again, then recalculating some of the depths, and she's still ending up with the same results.

First, what sign should the final result be - positive or negative? That will tell us which ones are incorrect.

Second, do you have any idea what would cause the incorrectly signed ones to be wrong?

Thanks,
Mike

[gmike]

Problem solved...

We went through all the calculations again, this time using both my daughter's calculator and mine. We discovered that we got a drastically different result from the tangent function on each. We went to a third calculator which agreed with mine. I had her redo all the calculations on mine, and now we have all positive depths that seem reasonable.