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Re: (meteorobs) To dew or not to dew...



GeoZay wrote>>skies were clear and calm...but very wet. I had to use the hair
dryer each
>time I advanced the film of my cameras.<<

Cathy>>I think I remember you commenting once that your rotating shutter does
help
keep dew down to some degree.<<

Yes it slows dew formation down...but doesn't prevent it. 

Cathy>>Up north here, in spite of being inland, we tend to get heavy dew in
summer
and heavy frost in winter.  For our telescopes and cameras, we need
something to not just take dew or frost off, but prevent it from forming.
Yes, the moisture is that bad up here.<<

A thought has just occurred to me...There are a few products that one can rub
onto car windows, Breathing Apparatus(BA) masks(for firemen), astronaut
faceplates etc that prevents the formation of dew or other condensation. I
wonder if they would work on camera lens without deterioating the coatings?
When I wear my BA masks on a fire, one of the big hinderances is the formation
of condensation that inhibits my seeing. Nowadays the masks have a constant
flow of air to prevent this from happening(supposedly). What I do as a
temporary fix is this: Before the fire in the course of my daily equipment
checkout, I would take a dab of some kind of liquid soap such as Ivory Liquid
and rub it all over the inside of my mask. Take a paper towel and rub it
completely dry and clean. What this does is put a very thin layer of the soap
coating on the face plate. You can now breath on it and condensation will not
stick to the mask. It will evaporate immediately. This is a one time fix. Once
I get a fire and use the mask, I will have to clean it up and re-do the
process all over again for the next time. Perhaps something like this can be
used or tried with camera lenses?

Cathy>>So, I got myself set up with a 'Kendrick' system.<<

The Kendrick system would work good too. 

Cathy>>It has a controller, a box with 4 plug-ins for individual heater
straps, and
will run either from a gel cel, or car socket (my favorite), or with a power
converter, from regular power.  Each heater strap has a long cord, with the
heater part being encased in a narrow 'cuff' that attaches with velcro onto
whatever you want it for.  The velcro attachable units come in different
lengths - for different aperature scopes, and different aperature eyepieces.
They work well on cameras too... you just have to be careful not to move the
focus off infinity on your camera.  The really nice thing about the Kendrick
system is that the heat is adjustable, so that you can leave it on just a
bit, or put it up all the way to high for severe moisture conditions.  <<

I found soldering 4 each 10 ohm, 2 watt power resisters in series and hooking
up to a 12 volt hobby battery works fine to remove dew. I insert the resisters
into a clear plastic tubing to form a loop. I have it sized to fit my lens and
wrap it around the front of the lens. This will allow the heat to gently flow
into the lens without any shorting out. 

I haven't tried it out yet, but you might want to experiment with the use of a
variable transformer(instead of the battery) that powers a hobby choo-choo
train set? I priced one recently for $30. You can hook up several systems if
you have multiple cameras? 

You also might want to consider purchasing the small chemical hand warmers for
about 50 cents apiece from a camping supply store such as REI. They are small
and last for about 8 hours. Take two of these and wrap around the outside of
your lens and held on by a thick rubber band. These are better than nothing. 

These are a couple ideas that I discussed in my Meteor observers guidebook.
Perhaps someday I will be adding something about the use of Ivory Liquid? :o)
George Zay