dew.

[bibbsy]

hi all,

a bit worried about the amount of dew that i get on the set up,most of all the HEQ5 mount,the mixture of wires,electrics and WATER scare me,are these built to be ok under these circumstances ? or is there a real chance and danger of doing damage to the mount.

thanks for any help with this

[hemihaggis]

hi there i stay in wet damp ,cold humid , frosty , swampy scotland , where percipitation and humidity far execced the warm dry climate that is essex , im sure you will be fine , lol its like the gobi desert compared to here lol .

ps i used to work in chelmsford , its still summer down there lol

[bibbsy]

thanks hemihaggis,just had visions of crackle,spark,BANG,new mount on the scrap heap lol

[JamesM]

The "....crackle, spark BANG" that you might hear will be your eyepiece case that you've just knocked over with all the excitement!

James

[Merlin66]

I was trying to get some spectra last week and the dew was running off the scope; the mount (NEQ6pro) was saturated and there was moisture everywhere.... the only thing that went "fizzle -pop" was my patience......the following morning a wipe with a dry towel sorted everything out...no issues....

[bibbsy]

lol james

thanks merlin,wont be so worried the next time im out there

[x6gas]

Hopefully these things are designed to handle the dew. I routinely leave my imaging rig running and go to bed leaving the electronics outside, often in heavy dew.

Things are running at 12v so there shouldn't be any crackling and banging!

[rfdesigner]

I work in electronics R&D, and I've built my own scope driver.

Water: not all water is equal...

Sea water is nasty stuff, corrosive, conductive generally bad news.

Tap water is better, but contains minerals which can coat things like optics if you use it to clean them.

Dew is, more or less distilled water, quite poor conductivity, not particularly corrosive etc... if I thought my scope was clean, I'd be happy to collect the dew from it and drink it... but my scope's not that clean!

Electronics: There are two problems

High voltage, if the working voltage is high enough then the current through the water can be significant carrying electricity to parts it has no business getting to.

High impedance, Many modern electronic parts do not take much current, so water conducting the odd electron into one of these high impedance points can cause big problems... If it 'confuses' a voltage regulator then circuits using that supply voltage could be over-voltaged and damaged.

Advice?...

Keep things as dry as you sensibly can. Scopes will get wet and will have been tested under dewing conditions, so one night of dew isn't going to hurt at all.. but I would want it to be kept in dry conditions for the rest of its life, either indoors or in an obsy, that way water can't build up.

For reference, my drive system in the early stages of developmend was tested outdoors with dew and no case or anything to protect the electronics.. needless to say the dew eventually managed to cause it to throw a glitch. Currently it's inside a plastic lunch box with wires poking out the side of the lid and can stand any amount of dew. But then it comes inside when I'm done. The hand controller is a different story as it has no high impedance points in it's design and hasn't needed any case to work reliably.. all very heath robinson.

hope this helps

Derek

[bibbsy]

thanks x6gas

many thanks derek,very informative and puts my mind at ease,at the moment im having to take all the gear out then bring it all back in again,hope to buy a pod in the new year,no setting up and no dew problem then

[Merlin66]

A pod may save the set-up time, but in this climate you'll still get dewing...

[bibbsy]

maybe i should not say pod im looking at the pulsar observatory,i didn't think that i would have a dew problem inside there merlin ?

[Merlin66]

When the temperature drops below the dew point moisture falls out of the surrounding atmosphere....both inside and outside the observatory...through the open shutter etc etc. Things will still get damp...believe me...

[bibbsy]

thanks merlin,

cant be as bad as standing in the middle of the lawn tho mostly looking forward to not having to set up and take down the gear....thats a pain.

[rfdesigner]

I think you'll find a lot of people run dehumidifiers or similar in obsys to keep them dry.

With a bit of luck I'll be building an obsy next year, but I'll definitely be working out how to keep it dry, and still be keeping all the camera gear indoors in a dry box with dessicant to prevent mould on the optics/sensors.

Derek

[bibbsy]

hi derek,

dehumidifier i also have down on the check list,i also have a mate that does paint spraying and uses those little gel bags to cut down moisture,he said that i can have as many i need as and when,cant hurt to throw those around in there also as they are freebies

[rfdesigner]

Ah yes.. dissicant bags, good for keeping small sealed spaces dry but useless for large volumes or areas not well sealed. It might be useful if you were to stuff them round the mount then cover it in a large plastic bag, remove the air and tie it down to seal as best you can, but it won't keep a shed dry. If you use dessicant you should also have humidity indicator cards so you know when they need recharging, or use dessicant with the inidcator dye built in.

(I've used these quite a lot)

Derek

[bibbsy]

thanks derek.......will there be any room left inside the observatory for me once ive put all this extra stuff in there lol.

[x6gas]

Ah yes.. dissicant bags, good for keeping small sealed spaces dry but useless for large volumes or areas not well sealed. It might be useful if you were to stuff them round the mount then cover it in a large plastic bag, remove the air and tie it down to seal as best you can, but it won't keep a shed dry. If you use dessicant you should also have humidity indicator cards so you know when they need recharging, or use dessicant with the inidcator dye built in.

(I've used these quite a lot)

Derek

'Scuse my ignorance but can these dessicant bags be 'recharged' by drying them out in any way or is the hydration of the silica gel a one-way process?

[bibbsy]

the ones my mate uses are just disposed of once full,dont know if there are other makes.

[rfdesigner]

Bung 'em in the oven at ~110C for a number of hours. To determin if they are fully dry, weigh them using electronic scales, they get quite a bit heavier when full.

I've only ever used an electric oven for this purpose.. Gas ovens create a lot of moisture, so I'm not sure how this would affect things.. physics suggests you should be ok but I'd want to test it before saying, hand on heart, it'll work.

Derek