Any idea what this is??

[iancandler]

Does anyone have an idea what this prism/diagonal might be used for?

It looks like some kind of Herchel wedge, its all solid metal, no plastic at all and was found in my late brothers astronomy gear.

[F15Rules]

Yes, it looks like some kind of Herschel wedge for viewing the sun and deflecting most of the light and heat.

The top nosepiece barrel has the look of a typical Nihon-Seiko Japan component (they built Unitron and Polarex scopes in the 60s and 70s)..such was the accuracy of their machining, no set screws were needed to hold diagonals or eyepieces in place: they were a simple slip/friction fit and the slits were to allow air to escape so the incoming eyepiece etc could slide in smoothly without getting held up by trapped air.

Not sure it would be safe to use now though. I think they were used with a glass solar screw in filter back in the day and would be seen as unsafe for use today.

I:m thinking this is a 0.965" fit?

It's value today would I think perhaps be to a Unitron collector who might want this to complete an original scope's accessories?

HTH:-)

Dave

[michael.h.f.wilkinson]

Herschel wedge, I would say. Newer models favour a vented enclosure rather than an open exit for the excess light. It should work, but nobody should get any bright ideas about looking into the beam of light emerging from the rear. You should also use these wedges in conjunction with a very dark ND filter (sometimes these are integrated). If such a filter is inserted after the wedge it might be safe, but I would myself prefer getting a more modern one, especially if it is 0.96". Unitron collectors might be interested, however.

[iancandler]

Thanks guys, its 1.25" fit, but I'll put it to one side as I dont want anyone to use it and damage their eyes.