Moin!
To serve several accessories side by side i ordered that 180 mm mounting rail (MENGS® BPL-180) yesterday:
https://www.amazon.de/gp/product/B00IR4WPG8/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
This rail will be mounted with a manfrotto 200PL quick release plate right on the tripod's head. To get a stiffer junction, I'm going to place some extra screws.
The rail will carry the scope at it's left side (also with an extra quick release mount) and the Helion at the other side. To adjust the Helion's collimation with the scopes view I ordered that leveller, which can be levelled +/- 15 degrees in height and 360 degrees around:
https://www.amazon.de/gp/product/B01GDVYJ56/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1
Maybe at the end of the week I can show some pics of that setting.
By the way, I ordered the 28mm Helion lens meanwhile and of course will share my experience if someone want's to know.
Well, does someone think the last posts strayed somewhat from the subject and maybe it was more helpful to others if I started a new thread?
Last, not least:
@Henning: quite a well done red dot mounting you showed us. I'm sure catching birds in flight is much more relaxed this way, despite the scope's angled view. This will surely be one of the next to-does optimizing my setup.
Cheers