This #1A Skylight Filter assembly threads onto the
rear cells of SCT telescopes and seals the interior
of the telescope from dust. This is important
because cleaning the primary mirror of an SCT
isn't easy. The filter also increases visual and
photographic contrast, decreases glare, and helps
to penetrate haze.
This filter assembly is threaded so that all other SCT
rear cell accessories can be threaded to this filter.
This filter is in excellent condition, price is $30
and I pay shipping.