If using an oddball wide angle lens that doesn't appear in the Nauticam tables, is there a method to work out where the dome port should sit in relation to the front of the lens? (to enable me to work out what extension rings I should fit?). Hopefully there is a method that gets at least close so as I don't have to do too much trial and error!

https://interceptor121.com/2024/01/06/methods-to-determine-the-appropriate-dome-port-for-a-wide-angle-lens-in-an-underwater-housing/

Might be some help there?

DYI forum has some more info buried inside threads like this https://waterpixels.net/forums/topic/3672-3d-printed-curved-glass-macro-port-nikon-60mm-n120/page/2/

Just now, Sokrates said:

https://interceptor121.com/2024/01/06/methods-to-determine-the-appropriate-dome-port-for-a-wide-angle-lens-in-an-underwater-housing/

Might be some help there?

DYI forum has some more info buried inside threads like this https://waterpixels.net/forums/topic/3672-3d-printed-curved-glass-macro-port-nikon-60mm-n120/page/2/

Many thanks - will check them out!

Since its been covered extensively in the links above and various threads, no need to repeat the process description.

Probably quickest to spell out the particular lens / camera / housing / dome combo you are interested in, and ask if anyone is using / can advise on how it goes.

There are many possible 'off piste' (off port chart) rigs, some of which work very well... and some which don't!