What’s a dew heater strip? And how do you use one to keep lens fog from your camera or telescope lens?
While the examples will show a dew heater strip for a camera, the same principle applies to a telescope. Obviously, if you have a larger telescope, you might need to purchase a larger dew heater strip or maybe connect two together.
When does lens fog occur?
Your lens can build up condensation if the glass is colder than the air around it and there’s some humidity in the air. There’s more to it than that, of course. These factors are tied to dew point and air movement, all of which also affect condensation.
What is a dew heater strip?
A dew heater wraps around the lens, keeping the body warm. It creates heat via a power source, typically by connecting to a small USB power bank. By keeping the glass warmer than the ambient air temperature, it prevents lens fog from forming on the front of the lens (or anywhere else).
I purchased a dew heater strip from minerlele a while back. As of this writing, however, it is currently unavailable. However, there are many other similarly-priced dew heaters priced at under $25 for you to use.
What power source does a dew heater strip require?
Dew heater strips should be used with a reasonably powerful USB power bank. I believe most USB lens warmers are 5V, and so are most USB power banks. Velcro the power bank to the leg of your tripod, and you should be good for the evening.
Dew heaters do not work well with a lot of lower-powered USB banks, such as the promotional types that people often receive for free. I use an Anker PowerCore 10000 for mine, which is powerful to last the entire evening when my dew heater is set to medium if necessary.
Is it easy to operate a dew heater strip?
Absolutely. Simply wrap the Velcro strip around the lens. Connect the USB cable to the power bank. The power light should activate.
Typically, you have three settings: low, medium and high. You also have an off button. That’s it!
In the field, I haven’t had to keep my dew heater on all night. However, it gives me great peace of mind to know that I can have it run all night on medium, which seems more than enough to keep the lens warm. This proved effective for photographing in very humid night conditions such as a forest in Georgia after rainfall or West Virginia during the summer.
Are there other methods of keeping lens fog from your lens?
Yes, there are. One method is cheaper and doesn’t require electricity. You can read the article Solving night photography problems: Three ways to keep dew off a lens here on Photofocus!
