Can A Telescope Get Wet?

Not really. You might be able to find specific telescopes that are designed to get wet and covers to protect them from the rain. But these are very uncommon and expensive.

As a rule, it’s best not to get your telescope wet. This is because they are predominantly made from metal which can rust. 

Can A Telescope Get Wet

Water can also damage the mirrors and lenses used in the telescope. The water can distort the lenses and mirrors and so alter the view through the telescope.

So, even if the outside of the telescope can be dried off, the water can get inside and damage it even more. So it’s always best to keep your telescope dry. 

Moisture can often form on a telescope due to its temperature. As they are made from cool materials, condensation will form on the body and lens of the telescope if the air outside is warmer than the telescope.

This is very common, especially during the warmer months of the year. There are several ways to protect your telescope from condensation and dew so it isn’t anything to worry about. 

How do I protect my telescope from moisture?

Your telescope can get wet if it rains but also if there is dew on the grass. The dew might only seem to be on the grass but it can get in the way.

There are a few different ways to protect your telescope from getting wet. One is with a dew cap, also known as a dew shield.

A dew cap sits over the lens and stops moisture from reaching the lens itself. Some caps have heaters that blow warm air onto the lens to dry the dew.

Depending on the amount of moisture, you will need one or the other. The heater won’t steam up the lens and is usually best for more moisture. Both types of dew caps are available to buy, but you can make your own dew cap to shield it from moisture.

Making a heated dew cap that blows out air is a little more difficult. But making one that just stops the moisture from getting into the telescope is pretty easy. 

You simply need something hard and cylindrical that is of a slightly larger diameter than the lens. Something like an old coffee can is perfect. You will also need some adhesive neoprene.

Cut the base off the coffee can and file it down a little if the edges are rough. Wrap the outside of the can in the adhesive neoprene. Place another piece around the inside.

The neoprene will keep the moisture from the telescope. It will also insulate the lens so that the dew is less likely to sit on the lens due to the warmth. This can also help during colder periods when the dew might freeze.

Do I need a dew heater for my telescope?

Dew heaters are a good idea but they aren’t essential. They are great for early morning viewings and excessive amounts of dew can potentially damage your telescope.

Dew heaters are great but you will need access to electricity and they are more expensive than dew caps. You can easily make your own dew cap (instructions for which are in the section above).

Why is my telescope foggy?

Dew and other forms of moisture can cause your telescope lens to fog up. Dew caps can stop dew from reaching the lens, but if you’re having a constant problem with fog and mist, a dew heater might be the best solution. 

Humidity can also cause the lens to become foggy. You can wipe down the lens in these cases but you can also adjust the zoom and settings to try and counteract the fog. 

How do you get moisture out of a telescope?

Sometimes it isn’t possible to stop your telescope from getting wet entirely, or it might get wet before you can even sort out a dew cap. In this case, the amount of moisture that has gotten into the telescope is important.

A small amount of dew won’t completely damage your telescope, so you don’t need to panic. If a small amount of dew has gotten onto the outside of your telescope or onto the lens, then you can just wipe it down.

This is a reason why it’s a good idea to keep a towel or cloth on you whenever you’re stargazing. Something soft such as a microfiber cloth will be best. 

If there is moisture on the telescope, point the telescope downward so that the dew can drip off. Make sure not to touch the lens or you might smudge it. The best thing you can do is to allow the telescope to dry out.

Place it in a warm space near a heater, but don’t point the heater directly at the lens or have it set too close to the telescope as this can damage the telescope. 

Don’t be tempted to dismantle the telescope to try out individual pieces. If the water is only on the surface or a little inside, dismantling it risks the water getting further inside.

It’s best to leave it to dry and then check on it. This is the best way to not risk getting the telescope even wetter.

Can you defog a lens?

The best way to defog a lens is to regulate the temperature. You can take the telescope indoors or sit with it in your car if you are away from home.

The lens fogs up when the temperature of the telescope is cooler than the temperature of the outside air. So, if you sit in the car with the air con on or go indoors, then the lens should defog.

You can, of course, wipe down the lens but it’s best to do this as a last resort. Wiping it down can cause the lens to become smudged and then even more difficult to clean.

Make sure to clean it with a lens cloth, rather than a towel or the corner of your shirt. This will give it the best clean. 

Gordon Watts
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