sony A7RIII close focus wide angle gear help

I have the Nauticam A7R III and the 180mm glass dome with Sony 16-35mm F4.

Don't have the sea and sea internal correction lens but plan to buy it as Phil Rudin seems to recommend it (thanks Phil!).

Will this setup be suitable for close focus wide angle?

If not, can I put a canon 8-15mm fisheye @15mm behind the same dome?  Or will I need a new dome entirely.

thank you.

The Sea & Sea lens is made for 230mm domes; AFAIK it will have marginal, or even negative effect in a 180mm dome. Technically, nothing is stopping you from shooting CFWA with your existing setup - you just won't have the same perspective as a fisheye, with the main subject in the center getting magnified, and lots of background around the edges at smaller scale. With a rectilinear lens, you can either get close and not have as much background, or shoot from a bit further away and have a more balanced scale between foreground and background.

The 180mm dome is not a good fit for a fisheye lens, as it's a smaller section of a larger diameter sphere, rather than a 180 degree hemisphere. If you put a fisheye lens behind it, you will get severe distortion and possibly vignetting from the dome shade. If you want to shoot CFWA with a fisheye, look at the 140mm fisheye dome and the appropriate extensions. Being a hemisphere, it will allow you to place the fisheye lens in the exact center without vignetting, and being relatively small, it will let you get very close to subjects for maximum magnification.

If I recall correctly Phil uses the S&S lens with the larger dome and the benefit with the 180mm lens is a lot less.  There are posts on the forum talking about the S&S lens. 

As for CFWA this is really going to work best with a fisheye lens in a small dome,  the small dome allows you to get significantly closer.   These setups will focus down to right on the dome.  An alternative might be a WWL with the 28-60 as that also focuses right down to the dome. 

Another advantage of using a small dome is that, usually, it allows you to get the strobes nearer to the dome and therefore nearer to the subject. CFWA lighting can be quite tricky - and the small dome does assist with this.

hmm ok thank you all!  seems like I'll need a new port and lens if I want true CFWA.  and maybe I wont buy that sea and sea correction lens.