Not sure I've ever seen a residential 200 amp panel with 80 circuits. I have seen plenty of 40 space 80 circuit panels but those allow use of tandem breakers. My SqD 200 amp main panel has 40 spaces but is not approved for tandem breakers so I added a sub-panel.
I added a sub-panel for the observatory feeding it with a 60 amp line not that it needed that much but I also keep the camper plugged in so that's 15 max in itself. Everything else, computer, mount, focuser, CCD camera w/8 position filter wheel, dew heaters, roof drive system (3 ph using an AC motor controller), lights and receptacles (including 2 GFI) probably take less than 5 amps. But the GFI's can take a full 20 amp load if needed. You never know. The sub-panel in the observatory is 20 space of which I'm using 10. More is better and cost is usually less for the more common sizes. I think a 16 space was more money as it's not as popular.
For those looking to replace or add on to your panels, look for national brands and see if they are approved to take tandem breakers. A tandem breaker is usually a dual 115 volt 15 or 20 amp double breaker (2 switches) that fits in a single space. It can get you out of a pinch sometimes. But do not attempt to use one in a panel not approved because there is s very good reason for that and you leave yourself wide open to insurance issues should you ever have problems. And insurance companies love to find reasons to decline a claim.