Salvaging the Skywatch Project on

CELESTIAL NAVIGATION

The weather has obviously been even more atrocious this quarter than is usual for Seattle's dismal winter. Thus this assignment is being revised in the following manner.

- It is still worth 10% of your total grade, but it is no longer given such importance that you will receive an Incomplete if you do not do it.

- You now have two options for the Skywatch, either with simulated data (given below) or, as originally intended, with real data obtained by you in the real world; however, you cannot do both options. The advantage of the real data option is that you get up to 20% extra credit on the assignment.

- if you choose the simulated data option and yet have been able to obtain some real data (either Polaris or solar data), then submit a write-up about these data and you can earn some extra credit on the assignment

- Due date is still Thu. 11 March, for either option (Skylogs are still due on Thu. 4 March); if you are possibly doing a second skywatch for extra credit (as discussed in the syllabus ; write-ups are available on the class Web site), then it is also due on 11 March.

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The procedure is basically the same as in Part A of the original assignment, except now you have no idea of where you are, except that you were kidnapped several months ago while surfing off the coast of Washington State, and you've been kept in the hold of a ship ever since! But at last you've been able to get up on deck and take the data given below. Moreover, fortunately you have a watch that indicates Greenwich Mean Time (GMT), the time that corresponds to zero degrees longitude. Thus GMT is your basic reference, rather than PST as discussed in the original assignment. You know that the date is 19 Feb 1999 (by making notches in the hold all those months), and you also have a handy table that tells you for this date:

Equation of time: sun is 14.0 minutes slow compared to mean time

Declination of sun -11°24' = -11.40 °

The length of your gnomon is 8.4 cm. Using a plot of altitude angle of the sun versus time, derive your longitude and latitude on planet Earth. Check a map and report in which sea you are located.