Shutter-Time-Calculator VS OpenAstroTracker

(Online calculator https://calc.loef.photos/ says 20/15/7 seconds max for it's rule of & npf calculations: 500 (major)/300 (slight)/200(pinpoint))

Without a tracking mount you can use this calculator to determine what exposure time you can get away with without significant trailing. It depends heavily on the declination (basically the arc length between the north pole and the object you are pointed at), lens focal length, and pixel size of your camera.

This was a 14mm lens, most will say use 500 rule but I suggest you to use NPF rule if you want pinpoint stars(or it will have an option like slight trailing this is what I used) it showed 12 seconds I think, I went a bit over since I know 14mm is pretty wide and you can't see any trailing once it is wide

That method isn't that accurate anymore(some people use 400 or even 300 rule), but these days the recommended method is The NPF rule.

4) How to select your exposure length: If you take long duration exposures (let's say) 15-20s or something, what you will see are star trails where instead of pin pointed stars, you'd see them moving in a line, ruining our shot. To get sharper stars, either use the rule of 500 (beginner friendly) or the NPF rule (more accurate, but a bit more advanced). Make sure you take a few test shots, zoom in and check the focus and star trailing first before continuing.

I've made a Calculator some time ago that can help you decide on the expose times without a tracking mount. It might be usefull: https://calc.loef.photos/

Seeing might have also been just not good enough. I saw an app called nightshift. Pretty good indications of how clear the sky is actually. Also, indeed have a look at the 'rules'. 500 rule might be a bit too crude. Suggest to check your camera and lens specs and fill them in at: https://calc.loef.photos/

For anyone that wants to look at the details, the hardware and code on this one is all open source: https://github.com/OpenAstroTech/OpenAstroTracker

...at GitHub

Software

Here is the DigitalLevel addon, with the files you're looking for, on github: https://github.com/OpenAstroTech/OpenAstroTracker/tree/bd2f5f6694e6d3b48d44d4cb4f0637b45bb4ab15/Addons/DigitalLevel