Annular eclipse Nikon D90

just trying ..no pre planning to do the right way.. stacks and stacks of filters.. last count.. 3 polarizers of different sizes, plus 4 clored filters (from film days)..
lens is 70-300 Nikon VR Plus 2x kenko Tele converter..

so is my math right ? 300mm x 1.5 sensor factor = 450 x 2 teleconverter = 900mm?

or is is 300mm x 2 TC =600 x 1.5 sensor = 900 ah the resulting focal length i guess will be the same..

and yes I know about the ghosting etc...

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