I personally noted that it helps aligning the centers of the ota and target if I remove the secondary and bring the crosses at the visual back and the 2 reflected crosses at the target into alignment.
Without removing the secondary, i found that with just one cross at the target, it would be too imprecise to align the system.
It is not sufficient to just align the target to the primary. The visual back also has to look into the same direction as the primary . And because of the size of the laser reflections and their short lightpath, using just the reflections of the primary would be a bit imprecise for aligning the target plate..
Fortunately, after you have removed the secondary, the cross that is reflected from the visual back to the target has a longer light path and therefore it shows misalignment of the target much better (to me with sufficient precision). Since your imaging train is not perfect, use a tilting adapter at the visual back and the screws of the hotech target plate holder to bring the crosses at the target plate into alignment. Try to do this such that the transmitted cross at the visual back is also centered as best as possible.
In contrast to the two reflected crosses at the target plate, the transmitted cross that can be seen behind the visual back must not be algned very precisely.
You can adjust for slight off centering of the visual back by moving the corrector plate once the secondary is inserted.
After the alignment of the target and the tilt of the visual back, it is important to align the 3 dots at the visual back and the target plate, once the secondary is re-inserted. For this one has to center the corrector and to use the collimation screws at the secondary, and the tilting adapter at the visual back.
Moving the corrector mostly moves the dots at the visual back.
Tilting the visual back mostly moves the dots at the target plate.
Moving the secondary collimation screws moves both the dots at the visual back and the target plate.
Edited by Benni123456, 03 January 2021 - 03:29 PM.