Automated watering at night - does anyone do that?

Regarding the cistern pump: I really treated myself, it's from the very top shelf and still delivers at least the same punch on my 40m garden hose as the water supply line. Currently, the pump is hung about 40cm above the ground, which has now given me a reserve after my cistern was emptied; I use a classic dirty water pump (large dirt diameter, low delivery rate) for that – compared to it, only a trickle comes out, but at least I still have a supply now.

and last summer? I think you also had no rain for a very long time then. Can you refill then?

Last summer was absolutely trouble-free – as I said, a heavy rain is enough for two weeks without any rain, but the rain also waters the garden itself.

Until a week ago, in the three years since the garden was established, I never had a single dried-out blade of grass. Seriously. I have always made sure the roots grow deep and have listened to the advice regarding fertilization. For two years now, I also have a robotic mower; since then I need significantly less water, and the mulch layer acts like an insulating layer over the soil, letting much less sun through. This pleases not only the lawn but also the insects that live in it, which is why my lawn is much more populated with birds than the neighboring gardens because there are more insects in my lawn. Especially last summer, this was evident; my garden was the bird restaurant "Zum mundgerechten Insekt," where everything flocked.

if you only have as much pressure as the water pipe, that is rather little. Usually, house water pumps are sold. Deep well pumps are the right ones. Name your exact type. Only if you know the pump curve (max. pressure and flow rate) can you properly plan the irrigation. Just as an example of what "off the shelf" means: Wilo with over 10 bar pressure and 45m3/h. I have two of those. But in a normal cistern, a Tipp deep well pump with integrated control and pressure switch for under €400 is optimal. The cistern should have a coarse filter for rough dirt. Few have fine filters. In the irrigation system, a filter makes sense but it also works without one. I know many installations that have been running without an additional filter for years.

We had no rain for over 4 months and do not live in Brandenburg. Becoming slightly jealous.

So exchange [euch] and your neighbors can no longer steal.

I would rather recommend an autonomous system like Hunter Hydrawise. Here you can also access local weather data. We have these in use at several locations. The irrigation duration takes temperature, sunshine hours, wind, etc. into account... Until you have programmed that yourself, you'll go crazy..

A few words on that. I have a moderately complex Home Assistant system, can program yaml reasonably well, and I also like to "flash homebrew firmware onto an ESP with heavy soldering work" in the evenings sometimes. Precisely for this reason, I can only support what rick wrote: By the time you've programmed that yourself, you are ready for the insane asylum. Even something like "don't irrigate if there was rainfall x the day before or rainfall Y in the last four days" — that's easy to think of, but until it actually works (!) a few more evenings have passed where you could also be doing something with your family. And Hunter can also be integrated into HA. So if it becomes a controller, I won't hack it myself but will buy something like Hunter.

if you only have as much pressure as the water pipe, that's rather little. Most of the time, house water pumps are sold to you. Deep well pumps are the right ones. Name your exact type. Only if you know the pump characteristic curve (max. pressure and flow) can you properly plan the irrigation. Just as an example of what "off the shelf" means: Wilo with over 10 bar pressure and 45m3/h. I have two of those. But in a normal cistern, a tip deep well pump with integrated control and pressure switch for under 400€ is optimal. The cistern should have a pre-filter for coarse dirt. Few have fine filters. A filter makes sense in the irrigation system but can also work without one. I know many installations that have been running for years without an additional filter.

Unfortunately, I don't have the exact type at hand, the heating/plumbing guy installed it for me back then. Currently, I'm slowly pumping the cistern empty anyway, I want to clean it at some point, maybe I'll pull up the (currently switched off) pump to power wash the bottom, then I'll look at the type.

It's a pump without a pressure switch, I have a switch on top and when it's on, the pump runs. I don't know about a filter, I'll check if I take the pump out.