It is a pretty simple repair. You need to unscrew the top section of the eyepiece barrel from the main body of the PST. Once that is off you need to unscrew the retainer ring that holds the ITF filter in place. Usually the retainer ring has two slots in it that either a lens spanner wrench is used to loosen it or just a thin strip of metal that spans both slots. With the ring removed the old filter just drops out and you drop in the new one. Replace the retainer ring and just snug it up. don't over tighten it since you want the filter to be able to expand from any heat. Screw the eyepiece barrel back in place and enjoy the much improved views.
Here is a link to one of the many threads here that show the process https://www.cloudyni...nado-pst/page-3
Thank you. I could do it and I saw my first proeminences in three years.
But I noticed some slight Newton rings at f/10 for the first time too. Could it be because the new filter axis is slightly misaligned?