Professor Frisbee Time Calculation Example

Professor Frisbee observed the transit of Venus at the United States Naval Observatory. At first contact, called Ingress, he noted that the time on his chronometer was 8h 56m 45s. When the second point of contact occurred, that is the planet Venus was completely inside the Sunís disk, he recorded the time as 9h 16m 09s.

 In order to determine the elapsed time, he subtracted the times he recorded for the first contact from the second contact. For example:

9h 16m 09s second contact

- 8h 56m 45s first contact

 Since it is not possible to subtract 45 seconds from 9 seconds, it is necessary to "borrow" 60 seconds from 1 minute. The new problem is:

9h 15m 69s second contact

- 8h 56m 45s first contact

24s subtract the seconds

 

 

 Next it is necessary to borrow 60 minutes from an hour. This would look like:

8h 75m 69s second contact

- 8h 56m 45s first contact

0h 19m 24s time from first contact to second contact

 

 

 Now it is necessary to calculate the elapsed time from the second contact to the third contact. This is a simple subtraction and it is not necessary to use conversions. Subtract the second contact from the third contact.

14h 38m 57s third contact

- 09h 16m 09s second contact

05h 22m 48s time from second contact to third contact

 

 

 For the elapsed time between the third point of contact and the fourth point of contact, called Egress, it is necessary to subtract the time between the two points. Subtract the third contact from the fourth contact.

14h 58m 55s fourth contact

- 14h 38m 57s third contact

It is necessary to "borrow" 60 seconds from 1 minute. Therefore,

14h 57m 115s fourth contact

- 14h 38m 57s third contact

0h 19m 58s time from third contact to fourth contact

 

 

 Finally, calculate the total time elapsed for Professor Frisbeeís observation of the 1882 transit of Venus. In order to do this, combine the results from each of the previous time calculations. For instance:

19m 24s time from first contact to second contact

05h 22m 48s time from second contact to third contact

+ 19m 58s______ time from third contact to fourth contact

05h 60m 130s total time for transit of Venus

 

 

 It is necessary to convert 120 seconds into 2 minutes.

05h 62m 10s

 

 

 Next convert 60 minutes into 1 minute.

06h 02m 10s

 

This is the final 1882 transit of Venus observation time recorded by Professor Frisbee at the USNO.