>>4017161The ISS is very bright in the sky when it is passing over and illuminated by the sun. The brightest object excluding the sun and moon, actually. It's hard to miss when you know that it's passing over, unlike an airplane it doesn't blink and is just a relatively quick spot moving across the night sky.
Pic related was the scope i did the ISS pass in the OP with, costs 250€. Basically just used the eyepiece that came with the scope, added a 3x barlow for extra magnification and attached my phone with an eyepiece clamp, like these.
https://www.amazon.com/telescope-phone-mount/s?k=telescope+phone+mountOnly thing then is to make sure to be in focus before the pass happens and have exposure under <1ms to avoid blur as best as possible. Check apps like Stellarium to find out about ISS passes, the phone app actually shows you the direction with its gyro sensors, though that part is behind a paywall afaik.
