Ich sehe an hellen Objekten Spikes – ist mein Prisma defekt?
Concerning Amici prisms, there are two factors which can limit the use for astronomy. The first one is the optical quality, i.e. how good is the alignment of the optical surfaces. Most Amicis are made for terrestrial use, where our atmosphere limits the useable magnification to ca. 60x or 70x, anyway. So, it's fine if they don't show a double image up to ca. 100x, as such high magnifications can't be used.
Those prisms which are designed for astronomical use are designed for those magnifications which we can use for the night sky – ca. 300x or even more. This high precision makes our Astro-Amici star diagonals so expensive.
But all Amici-prisms – no matter how good they are – suffer from one design feature: There is a line going through the center of the image, where both sides of the prism surfaces com together. This may cause reflections or spikes. To some extent, this will always happen when a bright object like a star is viewed in front of a dark background like the night sky. This should be obvious only with very bright stars or planets, while...