A Samyang/Walimex/Bower 500mm 6.3 mirror lens, €90 2nd hand.
During daylight it's awfully disappointing because the photos are always slightly blurry and sort of misty.
Not so when pointing it to the stars: pinpoint and natural colours - just great!
The other revolutionary purchase will arrive today: a 14cm quick release plate with 2 1/4" screws.
This will hold the lens and my smartphone (as surrogate finder scope) side by side on the Nano.Tracker - to let me find Andromeda in the coming season!
I'm totally stoked about these 2 gadgets.
Not so much about the Nano.Tracker itself, also a this-year purchase.
Because it is not the Goto Alt/Az Merlin I really wanted but couldn't afford.