The images just above were there to show the level of telephoto I got. It's about 4.2x right now. Which is difficult to understand as the original lens was 18mm f0.7. I am using the same optical arrangements, just some more distance to focus it.
My main goal was to focus the image, adding telephoto was the only way to do so. The narrowed fov allows for panoramic stiching as well. Overall the angular resolution increases and makes the image better. The image perspection is also increased greatly because my phone screen fills a similar fov than the actual image. And so should the final image fill the same fov on your monitor once it's delivered correctly.
The only information I got from Bill was that it's a 18mm f0.7 build for a 20mm image circle on a >20mm sensor diagonal.
It's hard to calculate because I run this afocal, as an auxiliary lens... The Lepton lens block stays. I calculated that lens block to be a 1.7mm f2.0 some time ago, but without proper testing, it's guesswork and I don't have he optical test equipment to do so.
I am working on a new iteration where the rear element is fixed because I gave up on the idea of making it a zoom lens with just 3 elements in 2 groups, as distortion becomes an issue far too quickly. I do got more elements and I can also change their arrangement to build a zoom lens later.
I still have to come up with a mounting solution, that's difficult due to the uncommon design of the phone itself. Neither CAT nor Bullit was able to provide me with cad models or drawings so I can collimate the lens correctly.
I intent on just bootlegging the focussing mechanism from this Thorlabs zoom tube:
https://youtu.be/Vsn0em5d-P8 shouldn't be too difficult to model this... It's for a prototype anyway.
I am still interested in ideas for a test target, or a simple was to DIY something that allows testing for distortion and focus.