Guiding with a piggy-back telescope not only produces an offset between main and auxiliary telescope, it also means that this offset varies with elevation of the target.
 | 
With active guiding.
Without active guiding.
|
Guiding with a piggy-back telescope not only produces an offset between main and auxiliary telescope, it also means that this offset varies with elevation of the target. We now measured that variation and included it into the guiding algorithm. To the left, a 20min exposure of NGC 891 with guiding enabled can be seen, to the right an image of the same object just half an hour later without active guiding is shown.
