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Mirko,
There are only two basic variations in Solar Ha telescopes.
The majority (PST/ 60 SolarmaxII/ Lunt 60/50 etc.) use a smaller etalon assembly behind the main objective. This saves money.
The optical layout is then:
Front objective (AR coated), energy rejection filter(ERF) (Lunt designs), collimating lens for narrow band etalon filter, re-imaging lens and energy rejection filter (Coronado). At the eyepiece/ camera end of all the Ha scopes there's a combination of IR rejection and final narrow band Ha filter (usually called the blocking filter)
The alternative construction uses an external ERF/etalon which fits onto the front of the scope i.e. Lunt 35/ Coronado SM60 etc.
The blocking filter assembly is still used at the eyepiece camera.
Hope this helps.
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