Today I took out my Coronado PST, after may be a few years, to have a look at the Sun, as the morning sky was so clear.
The image was OK. I saw a small prom and some surface activities. Is the sun still in a low period? - I heard that since a few years.
But I just wonder. I bought the PST in 2009 (and used it almost every day in the first couple of years). Now it is 12 years already. Is there some sort of expiry date for a PST? How do we know if it still works well and safe? Do the filters deteriorate over time and make it unsafe for our eyes? Or if the image still looks good, that means the filtration is still working well and safe?