I recently moved to a property in a Bortle 4 zone. I'm retiring in three months. The house is on an acre of cleared land with 12 acres of woods behind, and with a creek behind the woods. The house is toward the woods side of the cleared lot.
The back yard is about 1/10th acre with a moderately good horizon to the south, Polaris is above the trees to the north, east over the house is not bad, but there's limited visibility to the west and north-west. The advantage to the back yard is that the house and woods block direct light from neighbors. The disadvantage is that the house and woods - especially the woods to the west and northwest - block my view of the sky. At this time I have a picnic table situated at the best position to block neighbor lights. For now, I intend to set up little table-top scopes on the picnic table for my family and me.
The front yard is about 1/3 acre and has lower horizons all around. But the neighbors on either side - especially on the northeast side - can have their lights on at night sometimes which produce direct glare when I observe in the front yard. I have good relations with the neighbor with the worst outside light problem - the one to the northeast - so I can text him when I want him to shut the lights off, and he'll do it. However, I don't really like having to ask every time I want a glare-free front yard for observing. And there are times when the sky doesn't clear until late at night. I really can't text him then.
I have an attached 24x24 garage which I use for storage and for yard equipment. No cars in the garage. But the garage is unfinished, with no insulation or temperature control. It is hot and humid in the summer and cold in the winter. I don't keep any optical equipment in there, just stuff like mounts, equipment bags and supplies. I store my telescopes and eyepieces on shelves around the living room and in the closet of my back office/den.
I am 100% visual. No imaging, and I don't plan on ever doing any imaging. I'm into deep sky, with some planet and double star work. I'll probably be getting more and more into double stars, mostly because I haven't put much effort into it in the past, and it might be interesting for me in my retirement.
My largest telescopes are a 10" f/4.8 Dob and an SW120ED. But I'll probably acquire a larger telescope in the near future. I'm not sure what it will be. If I have to take it in and out of the house, it probably won't be larger than an f/4ish 14" Dob. Chances are I'll eventually acquire a light enhancement gizmo. I'm not sure about a larger refractor, but if I get one, it would definitely be an ED/APO.
So do I need an observatory? What would be the advantages of an observatory in my situation? Where should I place it? What type would be best? I'm not much of a DIYer. Something prefab would be best for me. I'm not going to build one myself.
This is not something I'm going to do right away. I'm just putting the info together and getting ideas. Any help would be appreciated, as I know virtually nothing about observatories.