The first Apple Watch shows the current Astronomy face which features the time, month and date, and bottom toggles that switch between displaying the Earth, moon, and solar system and can’t be customized.
The second Apple Watch shows the Chronograph face with three complications (top left, bottom left and right) that can be customized.
The third Apple Watch shows a mockup of my ideal Astronomy face that isn’t currently possible. I love glancing at my Apple Watch and seeing whether it’s 96º or 74º outside. I also like seeing my Activity rings at a glance.
The other problem with Astronomy is that I love the moon version and never use the Earth or solar system version, but I often accidentally tap the toggles and lose the moon. Other watch faces like Motion use Force Touch (firm press) to enter the mode where you customize what you see.
Motion and other faces add complications (widgets) in watchOS 3 where customization previously wasn’t available, but Astronomy doesn’t change. I would love Astronomy if Apple changed it to work more like Motion and other faces.
(Side note: the top right stopwatch complication on Chronograph can’t be changed which is annoying. It’s too easy to start the stopwatch that I never need but I like the detail of the watch face otherwise.)