The Observatory was initially available for purchase at L23 but that changed with an update in September of 2016, you now need to achieve L30 before it unlocks in the Store.
Changes were made to the Hall production on 10/20/2017
Observatory Before = 12h, 1 Lens, 800m
Observatory Now = 12h 2 Lens, 1200m
The Observatory needs a Lens, crafted in the Lab, to begin production. Collecting from the Observatory now gives +1 Moon Rock (+2 if enchanted). The Moon Rock is used in Tower of Magic upgrade L6 - L8 build requirements.
Moon Rocks do not drop from Neighbors Observatory, it will only come from your own but drops every time.
Check Neighbors for a Large Library. These will drop Knowledge each time
You will need a total of (12) Magic Wands for build requirements, including the (8) used in crafting the Glass
Glass also requires Gemstones which are a very rare drop from Neighbors, it might be easier to just build your own Jewelers
The same is true of Measuring Tools. They come from your Hall or randomly and rarely from Neighbors. Since you need 15 of them, I would highly recommend building your own.