Thanks Simon. I hope that you had this pic lying around and didn't draw it yourself!!! Wow.
(Caveat - I'm new to all this astro stuff): I haven't used the Flat IV as yet, but I assume that the 66 to 86 incriments corrospond to the primary objective lens. I have an 80mm refractor.
I spoke with stever @ MyAstroShop and he suggested the 6mm spacer:
http://myastroshop.com.au/products/d...sp?id=MAS-005B
Assuming that I would normally use the 80mm stop, and because we'll be bumping her back 6mm with the spacer, I plan on adjusting the unit in 6mm to the 74 stop. How does this sound?
Or I may be way off because I don't really understand how the flattener's internal optics work... There are some complex elements in there...
Cheers.