Hello Nightowl4933,
While that may not be an automatic option for the Astronomy wallpapers, you may alternatively link a particular wallpaper to a particular Focus, such as the one of the Moon ones. Then, you can choose to set that Focus to automatically for a set time period, and this will automatically switch the Lock Screen to the specified wallpaper for that timeframe.
This page has details on linking the Focus: Personalize your iPhone Lock Screen - Apple Support
Link a Focus to your Lock Screen
Focus helps you concentrate on a task by minimizing notifications, or distractions. You can set up a Focus to temporarily silence all notifications, or allow only specific notifications (ones that apply to your task, for example). By linking a Focus to your Lock Screen, you have access to the features of the Focus when you use that Lock Screen.
1. Touch and hold the Lock Screen until the Customize button appears at the bottom of the screen.
If the Customize button doesn’t appear, touch and hold the Lock Screen again, then enter your passcode.
2. Tap Focus near the bottom of the wallpaper to see the Focus options—for example, Do Not Disturb, Personal, Sleep, and Work.
3. Select a Focus, then tap
.
See Set up a Focus.
You may also choose to leave feedback on any changes/enhancements you'd like to see. The best place to leave feedback will be at the dedicated site for it here: Product Feedback - Apple
Cheers.