(meteorobs) Colour camera advice for Sandia system?

[stange]

Chris has it right.

The only flaw in the all-sky camera PVC design is the junctions between the 
segments are not air tight seals. They should be sealed either with a thin 
gasket or a thin bead of RTV smoothed with a finger tip....AFTER you have 
made a satisfactory adjustment of all mechanical variables in the 
construction and camera alignment.

The internal heat from the Sun followed by the cooling night allows a period 
of time between off and turn on of the thermostat. During that period the 
inside-outside temperature differences cause an air exchange that contains 
moisture. This is especially noticeable after a rain. The internal portion 
of the dome can condense the moisture usually around the dome perimeter 
first. When the thermostat comes on, the moisture is gradually vaporized 
again but it still remains inside the housing to repeat the condensation.

I have a trace problem of this, but am reluctant to upset the calibration of 
my camera to disassemble and seal the airgaps. If I get a more important 
problem later I will seal it right.

I use those white granules in a plastic container lowered down next to the 
camea to remove moisture. The granules look wet afterward but care must be 
taken that NONE touch any metal surface. Highly corrosive.  -YCS


----- Original Message ----- 
From: "Chris Peterson" <clp at alumni.caltech.edu>
To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
Sent: 2008/08/27 21:17
Subject: Re: (meteorobs) Colour camera advice for Sandia system?


> An allsky camera should not experience fogging on the inside. If it does, 
> it
> needs to be opened and allowed to dry. Certainly a desiccant can be used
> inside, but it will probably only provide a small amount of protection. If
> the system is sealed and heated, it really should be fine. The main 
> problem
> is condensation on the outside of the acrylic dome. You need to provide
> enough warm air circulating on the inside to keep the outside surface
> temperature above ambient. It's a balancing act between the emissivity of
> the acrylic (and to some extent, the surrounding surfaces) and its thermal
> conductivity.
>
> Allsky cameras utilizing convex mirrors are very easy to keep dry, since
> radiant heat can be easily applied to the bottom side of the mirror, using 
> a
> heating pad or light bulbs.>
> Chris
>
> *****************************************
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
>
>
> ----- Original Message ----- 
> From: "Pat Branch" <pat_branch at yahoo.com>
> To: <cdnspooky at persona.ca>; "Global Meteor Observing Forum"
> <meteorobs at meteorobs.org>
> Sent: Wednesday, August 27, 2008 8:16 PM
> Subject: Re: (meteorobs) Colour camera advice for Sandia system?
>
>
>> To help with the fogging, I might suggest getting a bag of silica gel
>> from a craft store. Keep it at the base. When it gets used you can dry
>> it in a microwave.
>
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