Here is a recent similar shot(see post #3465) of Jupiter and its 4 Galilean moons. Have to "over expose" to get the moons; so next picture is as good as I can do of a more correctly exposed Jupiter with the 150-450 and 1.7x converter on my KP.
Although it was a hazy night, these turned out pretty well using a bhatinov mask for focus. All are really significant crops from the original view.
EXIF says 800 manually entered, as it is the closest choice to 450x1.7= 765mm by calculation.
Third is Saturn on the same night , same rig.