DSLR widefield dew solutions?

[dawson]

I tape those little hotties (heated chemical pads) to my lenses when doing star trails and the like, but they generally cool down after 2 or 3 hours and then the lens dews up. My favourite lens is too wide angle to have an effective dew shield, so I think I just need to get a heated dew strip for it.

 

I was thinking about getting one for the telescope too, but often I leave the camera away from where my telescope is, so really I need two dew controllers. I could use my existing battery (20amp hours) to run the camera dew strip, and get another battery to run the mount and telescope dew strip.

 

Can anyone think of a better solution?

 

I'll start looking for a second hand single port dew controller and heated dew band, and a multiple port one for the telescope.

 

James

 

[Guest Kheldar]

Heated dew strips is the best solution full stop

[dawson]

That is what I thought. I'll hunt for a second hand one today, otherwise I'll just order a new one as I want it before I go away in early September.

 

Thanks.

 

James

[xanthic]

I'll make you a controller. I've got a PWM controller breadboarded up. I'll just need to know the current draw.

[dawson]

AstroLeigh, that's kind, but you've got enough to do, and I'm sure I can find something cheap and cheerful (maybe not cheerful).

 

I'll have a think about it all in Pilates class

 

JD

[Guest peepshow]

Forgive my ignorance but how does a cooled CCD camera sensor  prevent dew

from forming on its cold sensor, as only heating  prevents dew?

[dawson]

The problem I am asking about is dew on the front of the lens of the camera (there is no telescope involved). The CMOS sensor in this set up is inside the camera body and largely protect from dew from the outside by the camera housing and the lens screwed onto the front of the camera body. I suspect any humidity inside the camera body itself could precipitate as dew on the sensor, but that is likely to be minimal.

 

As for cooled sensors (remember they could be CMOS as well as CCD) used in conjunction with a telescope, again the sensor is usually in a sealed unit behind a lens at some point. Either the telescope (refractor or SCT/Mak) has a lens at the front where the outside environment precipitates dew at the front of the scope but protects the rest of the kit behind it from dew, or in the case of a reflector dew could travel through the tube and up the eyepiece holder to the camera, but most cameras as far as I'm aware have a lens (glass plate of some description) in front of the sensor; in that case I'm not sure what mechanism prevents that transparent plate from dewing up, but it is some way inside the depths of the kit and that alone may prevent significant dewing.

 

James

[Guest peepshow]

Thanks James, for that. Of course the the colder the sensor, which is a good thing, the bigger the potential condensation

can be.    I did wonder if any one has ever tried using a Peltier dehumidifier generating  small, gentle air flows directed onto the

equipment's dew vulnerable parts.