Hi Etudiant,
I think there were reports in ATM and in JBAA amongst others.
But Horace may have started making them about 1930?
I haven't looked for these reports.
The main problem is making the ray tube optics and extremely careful baffling.
This allows their use in daylight.
Horace also routinely aspherised or tuned up the optics, so I am not sure a commercial variant would be cost effective.
His scopes mostly had upright images, even the astro scopes.
Similar designs are used in space telescopes or possibly military versions.
There are some Dall pocket scopes in the Science museum, London.
He took these pocket scopes on cycling trips across Iceland and Lapland where he used dry river beds as his road. Also Patagonia where he met Helena his second wife.
I think he was a widower before that.
He didn't have a car driving licence. He mainly just walked long distances.
Horace made his optics as good as the final product needed to be.
I bought a 90mm short focus refractor. It had HD in pencil on the side of the objective when I cleaned it.
The performance was poor.
I took it to Horace. He said come back in a week.
He told me that it was made as a low power finder for a large scope.
It was made from a large photographic lens he happened to have and the glass had striations.
He refigured it locally and it became a good but not excellent scope. It is O.K. at 100x but not 300x as his best scope would be. He said this was the best he could make it.
He would not take payment, but on my next visit I gave him some Ellore rugs to match the ones he had.
Regards,
B.