That's right. I handheld my iPhone 4s in front of the T2 adapter on the mirror telephoto lens
Bower 500mm f/6.3.
The phone has a wonderfully small pixel size of 1.5 um and I was trying whether it's feasible to use it as planetary imaging camera with my mirror lens.
In theory, it should work. There's stacking software even for iPhone planetary videos - like Registraxx called "Keith's Image Stacker".
It's just that this mirror lens has an obstruction in the middle and the iphone apparently can't look around it. (I wonder how my camera manages that, though.)
Would that change if the focal path were longer than the length of the t2-adapter? For example if I attached an additional 2x converter and mounted the iPhone on that - would that help to reduce the obstruction?
Would that happen with a proper Mak telescope, too, when I mount my iPhone on focuser or eye piece?