comet prediction and hurricane forcast - Make the problem cleare

How about change the problem from "probablity to see a star" into "probablity to see THE star"?

This is not a one-shot case. Here is the story.

NASA said the comet Xephisiss-231 would glide over night sky from 9pm-10pm on Feb. 3rd with chance of 0.9. The cosmetic event prediction is much more accurate than weather prediction because the physical model is simpler and governing equations are more accurate and linear.

But NASA cannot narrow down the Xephisiss-231 to the minute level like lunatic ecllips events. What is the probalility to see this upcoming Xephisiss-231 from 9:00pm - 9:10pm?