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Mount Anti condensation


philjay
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As mentioned in my post re my Observatory Mount (Celestron CGE) suffering from condensation on the electronics I have started on sorting this out to avoid permanent damage to the mount.


 


The CGE mount sits atop a 6" diameter steel pier, the top section was added to with a short extension when I changed from SCT to refractors in order to get a bit more height at the eyepiece when looking towards the zenith. This means there is a nice handy compartment where a heater can be fixed. However the pier top is closed with a massive lump of ali puck to accept the CGE electronics column.


 


So the 1st thing on the agenda was to drill out some holes in the puck to allow some warm convection air up into the mount electronics column. I gave up after drilling 2 holes fully out to 20mm, my drill was starting to sweat with the work so 2 big holes and 1 small will suffice I reckon.


 


pier%20top.jpg


 


I didn't want a massive heater in there just a nice small low wattage electronic enclosure heater of say 3W I reckon will do. I searched on RS and found their small self regulating 3w heater. This heats up to a surface temp of 75 deg C and would be ideal for this job I reckon. If its not enough they do 5 and 8W versions which I can change to if required. I made an thermally insulated bracket and here it is.


 


heater.jpg


 


 


The pier top I drilled out with several radial holes to allow cool air in to the chamber and covered them with speaker cloth to keep wigger wagers out. Then fitted the top plus heater and wired it up with a nice earth connection. Its a bit tidier since this photo was taken.


installed.jpg


 


It all tested nicely and the heater was starting to get the chamber warmish.


 


Next instalment is to refit the top then the mount, the mount is still by the radiators indoors at the mo drying fully before reinstalling.


 


The principle is that the heater warms air in the chamber, this rises up through the holes in the pier top, cool air coming in through the radial holes in the chamber sides. The warm air then goes through the electronics pier and eventually finds its way out of all the holes in the pier. Plus once the heater has been on for a few days the mount conduction will add to the effect as well, but theres a lot of metal to warm up before that will have any effect I reckon.


 


I will still keep a scope coat over the mount and water trap under the coat as belt and braces in case the mains should fail (being in the countryside does mean our electric supply is a bit hit and miss in winter.  


 


So hopefully this will all help to protect my beloved CGE.


 


More later


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looks interesting Phil, my mount electrics seem ok but my dew heater controller has given up the ghost (only 4 months old!) Keep us updated please?


 


Cheers


Ron


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A bit more today


 


The pier top back in place ready for the mount electronics pier


 


topon.jpg


 


 


I have removed the ali plate from the bottom of the mount electronics pier, this is to allow the warm air to rise into the electronics and pass out through the unoccupied sockets and holes. The ali plate was just stuck in with adhesive pads and didn't support anything so no probs about it not being there


 


electronics.jpg


 


The mount is still in the house  at the moment thoroughly drying and is now operating correctly with no spurious slews indicative of condensation. The damp looking patch in the photo on the inside of the electronics pier isn't water its drips from the conformal coating I sprayed on the boards last year.


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  • 11 months later...

1 year update. Has it worked then? YEP

The self limiting heater was switched on at the end of November and left on. The mount head is bagged when not in use and a condensation trap is used as a back up. The mount has had very little use for various reasons but for the first time in a long time it works every time I go out there. No strange slews or refusals it just works as it should. The condensation trap has only needed fresh crystals once this season so th7s little heater is doing its job.

Well pleased

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Observatories can be surprisingly unhealthy environments for telescopes and electronics, if you don't take suitable steps to tackle humidity and condensation problems.

You probably will hardly notice or bother if your garden tools go a little rusty in your storage shed, but leaving an expensive scope in an observatory needs a bit more thought and care.

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