ISS sighting opportunities

The question of the frequency of opportunities to see the ISS at different latitudes came up on a mailing list that I belong to. I decided to do a test using Quicksat. I did predictions for May, June and July, 2009 using my longitude and latitudes from 0 to 55 in 5 degree increments. I used 30 degrees elevation as the minimum that would be reported.

Keep in mind that this is in no way definitive. There are several factors not accounted for in this test. There are also variables that affect the outcome. One is the Earth's shadow and the effect that the seasons have on it. In the northern hemisphere The Earth's shadow limits the visibility of the ISS most in the winter and the least in the summer. In fact, it is possible at some latitudes and at some times of the year to see the ISS on consecutive passes. Another possible factor may be cycles in the orbit that affect visibility from a given location that are longer than 3 months in duration.

Anyhow, this is what I came up with.

Latitude    May   June   July   Total  Minimum   Maximum   Average

00            1       2        2        5       30               76              44.2  

05            2       2        2        6       40               87              61

10            2       2        2        6       32               85              61.3

15            2       2        2        6       35               63              46.5

20            3       1        4        8       31               87              50.9

25            4       2        4      10       30               86              72.4

30            6       3        5      14       31               86              46.4

35            4       2        6      12       32               86              55.5

40            9       4      10      23       31               85               44.6 

45          14       5      23      42       31               87               41.6

50          26       2      37      65       31               82               57.5

55          14       0      12      26       34               43               34.5