Doh!

[philjay]

I acquired a 1970/80s Konus 90mm refractor lthe other week with a view to just cleaning it, sorting mount probs, having a play then fleabaying it.

The objective was OK but very  dusty on both sides so it had to come out.

 

Now I have taken more objectives out of cells than some folks have had eggs for breakfast so I know the pitfalls but I thought I was safe here.

The lens set is held in with a screwed ring so I set the lens spanner to the right distance and carefully tried loosening, it..............................

 

Chink.

 

Although the ring wasnt tight the back face of the flint glass shattered into flakes as can be seen in the pic.

 

I said to myself "How bothersome"

 

One telescope wrecked.

 

On inspection the elements were a very tight fit in the ali cell plus Konus kept the expense down and although the edges of the crown glass were bevelled the back of the flint wasnt plus there was no protective gasket/ring between the quite rough cell seat and the flint. So when I relaxed the locking ring it was enough to shatter the edge.

 

 

Oh well all down to experience, glad it didnt cost much.

 

[Nightspore]

Bad luck. These thing happen I suppose.

[+Graham]

That's a PITA.

Is the back of the flint glass flat Phil or curved.

If it is flat I might be able to grind and polish it back.

[philjay]

Flat Graham. The clamshells are deep in places. It,d take a lot of grinding and then polishing, not really worth it for the quality of glass. If they had bevelled the edge, this wouldnt have happened.

Still, Ive got an old wooden legged eq1 a couple of eyepieces and a useful 90 mm tube out of it 🙂

Edited March 8, 2022 by philjay

[+Bino-viewer]

Sorry to hear of your mishap.

 

Its a good job it wasn't a Takahashi......😉

[Werisit]

That's a shame. You could make a stop down ring if you don't mind loosing a bit of aperture.

Alan.