I have an 8MP mono CCD camera and 1GB without zram is good enough for Ekos + PHD as long as I don't run Chrome browser. With my PI4 which has 2GB RAM and no zram, I have plenty of memory. Make sure that you enable System monitor on Mate panel which shows both CPU and memory so you can monitor memory closely. Keep in mind that Linux reports memory usage in a very confusing fashion - it considers buffers and caches as non-free memory even though it can be used if the system runs out of memory. In Mate panel buffers and caches are shown as light green.

I'm seeing 104F/40C with the fan blowing in (out, I get about 8 degrees warmer). I haven't patched the new firmware yet.

Hmmm, the case fan should be pulling the air into the case through the heatsink and out, so the fan should blow out of the case... well mine does anyway and does not go above 52 degrees...

Yeah, I've heard that. I tried both ways and tested the temperatures and I get about 8 degrees cooler with the fan blowing in. Now I do keep my house at 72 degrees with the air conditioning, but the test was done with the same room temps.

Would not blowing in be more likely to bring in dust/debris? Of course air still comes in to replace the outgoing air in that configuration, but it is lower velocity.

There are no moving parts in the Pi so it wouldn't affect it. Noncunductive dust here and there isn't going to short anything.

Thats a good point, but it wouldn't help the thermal issues. What do you think about dew? I'm not sure if it would make a difference for that one.

I do want to make a cap or some kind of dust filter. I also opened the top of the case to match the fan.
I finally got outside last night... and the temperature didn't go above 104F/40C all night. Now it was about 65F/12C outside, so that helped.
I did see interesting memory readings. I seems it grabs chunks of the total memory, works on that till it gets to a point and goes and gets more. I thought I was running out of memory (I have the 4GB version), but no, it just went and got some more (I thought I saved my memory reads, but the file didn't write like I thought).
I turned on DSS colored in KStars, that did slow things down a bunch, but nothing like the lockups that I saw in the 3Pi.

This guy did some heat tests on the RPi4:
Dew shouldn’t be an issue, the Pi temperature is too high for that to happen.

Blowing on the board makes more sense to me now that I think of it in it's case. Sucking air will only pull from the cracks near the USB ports and other plugs, but not from around the board, since it sits pretty tight in the case. This now has air is blown directly on top of the board.

I tried a thin T-Shirt filter and the temp went up by 10 degrees right away.
I hot glued this screen (at least it keeps the bigger bugs out) and the temps stayed the same.

It is a $50 computer. If you are that worried about dust affecting the electronics, maybe find a different device. Or get a closed case with passive cooling like the FLIRC.

I added one of these DockerPi power boards. It has a fan directly on the SOC and takes 12V to supply reliable 5V @4A for the Pi. Also has a safe shutdown switch and IR remote. Some modifications will be required in your case for it though.
www.aliexpress.com/item/33044617020.html...1.0.0.ec094c4dxG7c9J