NavList:

Thanks Greg,

That is great. I did not find the SI on my Google search.

Apparently it is either on loan or in storage.

Anyone planning a visit to the SI in the near future? It would be great to obtain accurate high definition photographs or scans, with the rotas moved off the base plates, and both sides of the base plate shown. It should then be easy to build a replica.

The SI model is dated 1945 and looks like the one described in the Luykx paper. If so, the paper suggests the other (B) side of the baseplate is identicle but the rota appears to be running in the opposite direction. The index tells you which side to use depending on various parameters.

re accuarcy, well Luykx claims mean errors Hc of only 2.6', The only way to find out is to build an accurate replica and do some tests as per Luykx. I think this could be really interesting.

Any help from anyone near Washington or with insider access to SI for getting pictures etc would be wonderful.

So far this is the only example of the device we have managed to locate.

I am very keen to build a good working replica.

Best wishes

Francis