[Merlin66 (Ken)]

The "boss" is not allowing me to spent too much time in the shed! so I've been cleaning out some boxes etc.
Came across my very first "spectroscope" - can't say built, but put together in 1978. It's a film canister cut to fit a 60 degree prism so that it can sit behind the eyepiece. I got the "idea" from Hartung's book ( original edition, p37)
(BTW I also built, and still have the double star micrometer based on his description, p38)
Works well and shows the lines in the brighter stars, as well as making Planetary Nebula much easier to find!!
The latest is an objective prism, a 7 degree, BK7, 18mm max. thickness, 110mm diameter ( Picked up from the States early last year...but it lay in the box!)
I've made a mounting cell from a 100mm PVC joiner, dremmeled the inside diameter to 112mm to fit the ED80.
I've already tried it out with my 50 micron source on the old Foucault tester and it looks promising!!
I'll post a couple of images later.
Still cloudy and raining over here... a bit like Melbourne.