Dew Shields (dew caps) trap stagnated air in the front of the telescope. The temperature of the stagnated air is slightly higher and is enough to prevent dew from forming. Dew shields can be use as a shade to block stray light from entering the telescope or during daylight torrential viewing. Stay light lowers image contrast. ATOZstars Flexible dew shields are made of black close-cell light weight foam rubber sheeting, which is non-reflective and a good insulation material. The foam rubber sheeting forms the cylindrical shape with Velcro. The dew shield rubber sheeting is slightly elastic which allows a snug fit on the telescope tube. The dew shield can slide forward as dew shield or slide back onto the telescope tube on most telescopes to protect the telescope from accidental scratching of the telescope tube. The flexible dew shield can be store away easily by roll up tight, lay flat or stays on the telescope. Rigid dew shields are difficult to store especially large ones. This dew shield is compatible with Celestron Evolution 9.25" dew shield. Celestron Evolution 9.25"