The transit starts at 1906 UTC (3:06 pm ET) and ends at 1953 UTC (3:53 pm ET), so it's at a perfect ...
Nth is the image cadence. This is not a required field. However, if a number is entered into the field, for example 5, the application will return one in every fifth image to the user.
There is a total limit of 500 images per query.
The 4096 images are only available for archive download.