Outdoor timelapse -- protection from the elements?

[genekogan]

Hi all,

I am in upstate New York with my Canon Rebel Xsi, and I'd like to create a timelapse of the stars (starlapse, you can see these on youtube/vimeo). I have an AC adapter and extension cord from the house, and special software for triggering them from my laptop (EDSDK). I'd like to leave the camera outside overnight to collect pictures.

My only concern is protecting the camera from the elements. It should not train, but it gets moist and dewy overnight, and I am wondering if the moisture in the air could damage the camera or the lense. What precautions do I need to take to protect the camera, if any?

 

[WayneF]

You could get it started and then cover the camera with like tin foil or plastic wrap, except for lens opening. Definitely use a lens hood. I am assuming the general case is not aimed straight up, but otherwise, you could add a plain IR filter.

 

[KmH]

The XSi is sealed well enough that it's not likely any dew that forms on the camera will hurt it. In the morning just wipe off the dew with something absorbent.

As mentioned you could use a DIY OP/TECH USA Rainsleeve - 18-Inch (2-Pack)

A plastic bag with a hole cut for the front of the lens should work as a DIY solution.

 

[Designer]

Maybe a loose-fitting tent suspended over the top and a small electric heater set to low. It won't take much heat to discourage the dew. Make sure the heater is not going to touch any part of the cloth.

 

[TCampbell]

For astronomy, we use dew shields, dew heaters, and hair dryers. Dew shields are typically our first (and least expensive) line of defense. That's just as simple plastic hood to keep dew from settling on a surface. But as the surface gets cold enough and depending on the dew point, dew will form on the surface whether there was a "dew shield" or not. Also the shields work well when the scope scopes are not pointing too high in the sky. If we point straight up to the zenith then our "dew shield" effectively becomes a "dew funnel" and we get dew anyway. When I'm observing all night, I'm very careful to limit the amount of time the scope points at objects which are directly overhead -- usually keeping this to 5 minutes or less.

So the next line of defense is the dew-heater. I'll spend some time explaining this below, but think of an electric blanket type heater... but wrapped around the lens. It turns out we don't have to heat the WHOLE lens... just the front most element. In fact... too much heat will create "heat currents" and distort the optics. So the trick is to have "just enough" to keep the dew away... but no more.

Lastly, if we blow it and end up with dew anyway... we pull out the portable hair dryer. That's basically just the defroster on your car. Blast the glass with hot air for a few seconds and the dew will evaporate right off and you can keep shooting. Of course those frames captured while the glass was fogged are going to look bad.


So back to those dew heaters...

There are LOTS of these no the market, and you can even make your own. I use "Dew-Not" heater straps wrapped around my optics. (Order Dew-Not™) The straps (nearly all of these wrap around a lens or optical tube with velcro) are placed near the front of the lens... just barely behind the objective lens element. That's the element that you want to have "warmed" by the heater. As long as that front-most element is warm, dew will never settle on it. If the strap is too far forward of the element then much of the heat will just escape to the air. That's why we position the strap to be just barely behind the glass.

The dew strap runs on 12v system power (a 12v battery -- which usually actually puts out 13.8v DC when fully charged.) But for "all night" you'd be better off with a 12v adapter like a Pyramid power supply. Something like one of these: Amazon.com : Pyramid PS9KX 5A/7A Power Supply with Cigarette Lighter Plug : Vehicle Audio Video Accessories And Parts : Car Electronics Note that which one you get for a camera isn't that important... it needs to be 12v system power (which means the power supply probably pumps out 13.8v DC) and it needs to have enough amperage to power the strap. But a dew strap for a camera lens would not take much power... certainly less than 1/2 amp.

The next problem is regulating the power on the strap. We dial the power up and down via a dew controller. The controller is actually just pulsing the power (you get full power for a fraction of a second, then it's off for the next fraction of a second... and just continues to cycle on/off to "pulse" the power to the strap.) This is the "expensive" part because most DEW controllers tend to be around $100-150 (a few are a little less... many are much more.)

The dew controller for my larger scope is built into the scope (made by Astro-Smart but they also make an external controller for about $150). But my smaller scope uses a stand-alone controller. I have a Dew-Buster controller for my apochromatic refractor: DewBuster That's a slightly higher end controller... most controllers are simple and the dial just controls the pulse rate. This controller is a little smarter in that it uses temperature probes... one measures the temperature of my scope optics... the other measures the ambient temperature of the air, and I set how much warmer I want the optics to be above ambient air temp. It provides however much power is needed to reach that goal. But that controller is over $200 (I see they've gone up... I'm sure I didn't pay that much for mine.) A Kendrick Astro "micro controller" might be a bit more economical: Dew Controllers - Premier, DigiFire 10 Controller, DigiFire 7 Controller, Standard Dual Channel Controller I think that one is about $90. It's a single channel controller but that's ALL you would want for a camera. (multi-channel controllers allow us to hook up multiple devices and control the heat to each device independently... e.g. I have a another dew heater on my guide-scope, another on my finder scope, and another on my eyepiece. I may be heating four devices at the same time... and since my main scope is a 14" aperture, it uses a very large dew strap that draws a lot more power than anything else -- hence I need to set a lower power level for my guide-scope, finder, and eyepieces than I do for my main optical tube. But a camera is just one lens... you only need one channel.

BTW - you might have noticed that my dew straps and dew controllers are not the same brand. That's because they all run on 12v system power and they all use RCA "tulip" style plugs (phonograph plugs). With very few exceptions, it doesn't matter who made the controller vs. the straps.

You can also find instructions to build your own dew controllers ... it's a relatively simple device.

The bottom line is... as long as the surface of the glass is warmer than the dew point then dew will not form on that surface.