What is it in my B600?

[Merlin]

I have a LUNT B600 that I wish to use in a PST mod. I inspected the blocker yesterday and saw two patches of "condensation" ( but probably not condensation ) on the inside of the optical window at the front end of the blocker.

Does anyone know what this might be? I'm familiar with the innards of the PST mini-erf/blocker assembly, but not of the B600. Should I take the back plate off the B600 to inspect?

Where is the location of the ERF in a B600? I'm assuming that it's somewhere behind the optical window, rather than being coated onto it, but I may be wrong!

Incidently, please don't confuse me with solar expert Ken ( Merlin66 ).

[michael.h.f.wilkinson]

Not familiar with that, but I do wonder if it is the "rust" problem you sometimes hear about. Why not put up a few pictures, and perhaps PM Merlin66?

[Merlin66]

Merlin,

The Lunt blocking filter assembly is very similar to the PST filter - an ITF (Interferenece Transmission filter) up front followed by the narrow band sorting filter.

Unfortunately what you are describing is the typical failure mode of the ITF.....

It's a compound construction and an edge seal protects the inner coatings - if this edge seal fails (due to thermal loading, mechanical stresses etc) them moisure/ humidity can quickly cause the filter to fail - the deterioration usually starts towards the edge and travels towards the centre...

Many have been successfully repaired by Lunt under warranty. It would be worth checking with your supplier.

Sorry to beak the bad news....