Hi Mike,
Depending on how strong the signal is, and what sort of structures are in the way of the signal, perhaps a high gain antenna could be used, on the receiving (observatory) end.
If there are any metal structures in the way of the signal (steel/metal fences, walls, roof etc..), perhaps you could reposition the modem/router within the home to improve signal strength outside the home.
I would grab a laptop with wireless capability or your smart phone and have a walk around outside to test / map wireless reception, possibly with the aid of a phone app for wireless signal strength and then take it from there, with any high gain antennas or amplifiers , etc... Of course if the datalink is critical then there's no beating cable.
Also if using a wireless antenna at the observatory (whether USB type aerial or Computer card (SMA?) plug in type antenna) you may be able to increase the antenna's directivity with a reflector of sorts and thereby increase the signal received. I once did this at home many years ago, but the other way around (on the transmit end) with a simple hand made metal parabolic reflector when wireless devices weren't what they are today. It might get you that little bit further. Some diehard wifi-ers use Pringle cans to improve signal directivity and strength.
Best
JA
PS:
I just saw your picture - the steel roof doesn't bode well for signal strength. I would try to get clear line of sight from the modem/router to the obsevatory (perhaps at the window) and test the signal in the current location versus the hopefully vastly improved (?) window or other unobscured location. Another thought: Your wireless modem router may have the option to also use an auxiliary external antenna which may help.
I haven't tried one, but here is another possibility: a wifi booster....
https://www.telstra.com.au/support/c...t-wifi-booster