Telescopes are amazing pieces of technology that allow us to glimpse parts of the universe we would otherwise not be able to see clearly. But, just like any piece of tech, there are some downsides that need to be addressed. One of the biggest problems amateur astronomers have with telescopes is dew and fog. Here’s how to prevent moisture on your telescope from ruining your view.
1. Don’t keep your telescope in a warm environment.
This sounds wrong, doesn’t it? Shouldn’t you protect your telescope at all costs and keep it in a safe, temperature stable environment? Not necessarily. Temperature difference is what causes dew in the first place. If your telescope is warm and the air outside is cold, the moisture in the air is going to condense on your telescope, leading to dew and poor seeing. By ensuring your telescope isn’t significantly warmer than the ambient air, you reduce the chances of dew forming.
2. Add a dew shield.
Newtonian telescopes rarely have dew problems because the optics are way down in the tube. Other telescopes don’t have deep tubes, so what you can do is extend the tube and provide your optics with additional protection. If you keep the air in front of the optics at a stable temperature by shielding them with a dew shield, dew won’t form.
3. Try a dew heater or a heated dew shield.
The best way to combat dew is to use double prevention. A dew heater keeps your telescope at a stable temperature, while the shield aspect extends the tube. Dew heater strips are options as well, but they don’t offer the added protection provided by a shield.