Deep space photography, what does it mean that the equatorial plane crosses the sky?

I guess, it may be in the following background that the shooting of deep space celestial bodies needs long exposure, and an equatorial telescope is needed to track celestial bodies in this process. With the movement of celestial bodies on Sunday, the positions of celestial bodies will change. When the celestial body passes through the transit, the equatorial telescope will also track the transit. It may be that the hour angle of the equatorial plane also exceeds zero, so it is said that "the equatorial plane crosses the transit".