http://www.n2yo.com/passes/amateur-radio.php
>What is the difference between dark yellow and less yellow?
There is a legend under the table. This is actually useful
for optical seeing. Dark yellow is excellent visual pass,
less yellow is not that good. Not too useful for ham radio,
but its there just in case.
>Where do I set the latitude and longitude of my QTH?
The location is automatically detected from your IP address.
Most of the time, that is good enough.