@jdsoubeyran 👍🏻 Better follow supplier’s instructions indeed. I do not know the Baader VIP Barlow except for it’s good stuff.
With a Barlow, the distance given is to obtain the Barlow factor e.g. x2 in your case. If you have more distance it will increase the actual multiplication effect, which is not bad with an ADC working better at high f/d.
The best is indeed to test In Real Life.
Same for me on French Riviera, it is either ☁️ or 💨. Neither are good for high resolution images.
Clear Sky 👋🏻