SolarChat!

Hello!

My PST is currently on service by Bresser. Original ITF is "rusty" abd needs to be replacet with Beloptik ITF.

In the future....is it wort protecting replaced ITF filter with something like Hoya or Marumi 52mm UV/IR Cut filter placed in front of the PST objective?

What's the reason of the failing ITF filter...overheating...."too much" UV and IR light passing through sistem?

Clear Skies!

Greg

Gregg,
The ITF fails due to a breakdown of the edge seal (probably caused by heat load or some other condition), this then allows the ingress of moisture which causes the failure.
ITF filters can last from months to years.
Adding a UV-IR to the objective would help but it needs to be a quality optical filter - most of the photographic filters we've seen are not good enough.