Q:

How to get/catch event off screen element? 

I'm trying to make fixed table header and is it possible to catch event or catch element when you scroll down and table header goes off screen?  

A:

One method would be using a scroll event for the window, and check if the element is visible there. 
How to check if an element is on screen is answered here: Check if element is visible on screen
Here's how to turn that code into custom events entered_view and exited_view:
var $element = $('#some_element');
var is_visible = false;

$(window).on('scroll', function (e) {
    // Check if $element is on screen using code from other answer

    if (checkVisible($element)) {
         if (! is_visible) {
             $element.trigger('entered_view');
         }
         is_visible = true;
    } else {
         if (is_visible) {
             $element.trigger('exited_view');
         }
         is_visible = false;
    }
});

Once you get it working, you might also want to debounce the scroll event: Here's info about debouncing/throttling in jquery.