Quote:
Originally Posted by Sebbie
Quote: "The SCT Cooler has a filtered air intake and other design features which minimize the possibility of dust infiltration and direct the air flow away from the internal optical surfaces.. (it) draws outside air in through a high capacity fan."
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Well, there's filtered and then there's
filtered.
I've done some work in the middle east where ultra-fine red sand (so fine it can stay airborne for days in a true "sand storm") got right through some pretty good filtering systems and into electronic equipment enclosures. It also got through rotating joints into mechanical systems that were supposed to be weather proof! The sand was allegedly in the 1-10 micron range and I figure enough of it was close to 1 micron to get through the fine filters.
Typically, mold spores are in the 2 - 30 micron range (so I read - although opinions vary somewhat). I think I would want a ~1 micron filter (and a fan powerful enough to suck air through such a filter) before blowing it through my OTA. Basically, any true
HEPA filter ought to do the trick.
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Like you I am a bit uneasy about contaminating the inside of the tube in case of filter breakage.. sucking in pollen or small bugs is a bit of a worry at my location as I am surrounded by bottlebrushes and close to a local pond..  Will do more research re recommended maintenance cycle later.
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Inadequate filtering would be more of a worry rather than filter breakage, at least IMHO. Most mold spores are released at night - around midnight to 2am - right when we're observing! In contrast, most pollen is released during the day.
Out in a field with your telescope would be perfect for catching those pesky mold spores, so, for me, good filtering is very important. Until then, my OTA stays as closed as possible.