documents construction of a dew
shield for a Meade
filter slider. The goal was to find a
inexpensive solution to prevent dew formation on the RGB
filters. This project required about 30 min.
construction time and cost
less than $5, which was a considerable savings over purchasing
a commercial covered RGB filter wheel (generally over
Meade DSI Pro
summer of 2007,
Pro ccd cameras and RGB filter sets were on sale. I purchased
my DSI Pro camera at the sale price of $100 plus an additional
$100 for the RGB filter set (below photo). The
RGB filters are prone to radiative heat loss
formation because they are very exposed in the open filter
slider. One solution to reduce dew
formation is to purchase an enclosed
filter wheel, but these can easily cost over $100. I decided to
construct a simple foam dewshield to cover each end of the RGB filter
slider. In addition to reducing dew formation, the foam dew shield
reduces stray light from entering around the filter slider.
RGB Filter Slider Dew Shield
The dew shield is constructed from small rectangles of
underlay for laminate flooring. I cut two 7.5 cm x 9 cm pieces and
two 9 cm x 9.5 cm pieces (below left photo). Each dew shield
formed by taping together a 7.5 cm x 9 cm and a 9 cm x 9.5 cm rectangle
(below right photo). The reason the dew shields have one
side is to overlap the filters on the telescope side of the DSI Pro.
Without this overlap, the metal DSI case would prevent the dew shield
from completly covering the first exposed filter on the telescope side.
The completed dew shields were wrapped
with clear packing tape for added strength.
The below photos show the completed dewshields installed onto
DSI Pro filter slider. The dew shields fit very snuggly around the
filter slider, but do not make direct contact with the RGB filters. It
is only necessary to remove a single dew shield to advance the filter
slider, making this a very simple system to use. It is possible that
these dew shields could be lost in a strong wind, but since my
observatory offers good wind protection, this isn't a significant