This dewcap prevents the formation of dew on the Telrad, or at least prolongs the period until dew can form.
The dewcap can be positioned directly on top of the glass window of the Telrad. When viewing through the Telrad the dewcap is simply lifted, allowing you an unobstructed view while the dewcap still provides some dew protection even then.
The dew-cap is screwed onto the back of the Telrad.
You only need a regular screwdriver and no exotic tools whatsoever. You can leave the dewcap permanently mounted on the Telrad.
