RGB Filter Slider Dew Shield

RGB Filter Slider Dewshield Project

This webpage documents construction of a dew shield for a Meade DSI Pro ccd camera RGB filter slider. The goal was to find a simple and 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 $100). 

Meade DSI Pro Filter Slider

During the summer of 2007, Meade DSI 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 and dew 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 foam used as an 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 is 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 longer 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 the 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 problem.