High humidity can cause water vapor to condense on the telescope's optics, leading to fogging and decreased image quality. It can also promote the growth of mold and mildew, which can damage the telescope's components.
The best solution is to use a dehumidifier or a drying agent, such as silica gel, in the area where the telescope is stored. This will help remove excess moisture from the air and prevent it from condensing on the telescope's optics.
While a telescope cover can provide some protection against humidity, it is not a foolproof solution. If the cover is not breathable, it can trap moisture inside and create a humid environment. It is best to use a dehumidifier or drying agent in addition to a cover.
This will depend on the level of humidity in your area and how often you use your telescope. It is recommended to check the humidity levels and use the dehumidifier or drying agent as needed, especially during periods of high humidity.
In addition to using a dehumidifier or drying agent, you can also store your telescope in an airtight container with a desiccant, such as silica gel packets. This will help absorb any excess moisture and keep your telescope dry. It is also important to regularly clean and maintain your telescope to prevent any buildup of mold or mildew.