The first picture is made with a Zhumell 118mm Spotting Scope at 30x, with a Samsung Note 9. I took around 180 Light frames, 120 Dark frames, no Flat frames and i reused the Bias frames from the second pic.
The second picture is made with a Meade ETX 70, im not sure about the eyepiece, and the same phone. The light frames were 2 seconds because it would start trailing more than that and 800 Iso. I took around 120 Light frames, 100 Bias frames, 100 Dark frames, 20 Flat frames and 20 Dark Flats.
I think for the image quality to be better you should use the pro mode, if the phone camera has it or use a third party app that allows you to manually control the settings and also shoot in RAW format. When using the pro mode its also important to manually adjust the phones focus so that it is on infinite and doesnt move while you're taking pictures. For the exposure time its basically trial and error, take a pic and adjust the exposure till you see round stars no trails. The note 9 has an advantage that it has the s-pen and i use it as an intervalometer sorta, i can press the button and it will take a picture without having to touch the phone and shaking the setup, but you can get an intervalometer app or can buy one for cheap online if you wanna get a bit more serious about phone astrophotography. Hope this helps, if you have any other question feel free to ask .