The year’s closest conjunction of a planet with a first-magnitude star occurs during our August 11 daytime, which, as you’ll see, doesn’t matter much.
Jupiter, on the far side of its orbit from us and still moving slowly eastward against the starry background, will pass only 0.4 degree north of Regulus, the heart of Leo. Their closest moment is August 11 at 15 UT, which is 2 PM by clocks in Britain and 11 AM for eastern North America.
So you might think you could see these two points of light almost as close together in the preceding night (Jupiter just to the right – west – of somewhat dimmer Regulus) or the following night (Jupiter now having moved to the east of the star). But you surely can’t: they are only 11 degrees from the setting Sun.
The arrows, as usual, show the motions of the heavenly bodies in relation to the starry background, not to the horizon.
And this is because the Sun has, only a few hours before, barged into Leo. It crossed the boundary from Cancer into Leo on August 11 at 2 UT (which was in August 10 by North American clocks). The Sun will be just about in front of Regulus on Aug. 22.
We can imagine the mighty Lion glancing down as the puny star rolls toward his feet and one of its firefly planets disturbs the fur of his chest.