Hawksmoor

My old architectural practice was multidisciplinary (including mechanical, electrical and environmental engineers) and we designed a number of archive facilities which had strict environmental controls regarding relative humidity and temperature. I have some experience , some success and more than a few set backs in battles with condensation. The key issues are the relative humidity of the air and the surface temperature of your kit. In my backyard where I observe the relative humidity is often somewhere between 85 and 95% at this time of year. As soon as I take out my scope or cameras they start to radiate heat out into space. At some point in time the glass will cool and reach the dew point (the temperature at which the moisture in the air can no longer exist as a vapour). Irrespective of the amount of thermal insulation or the thermal mass of the glass at some point in time the dew point will be reached and condensate will appear where I don't want it. Thermal collars and the like which I have made delay the inevitable for about a hour and a half for the smaller bits of glass (camera lenses, my 66mm refractor and 60mm guide scope) and approximately 3 to four hours for my 127mm refractor's objective lens. The only way to prevent this happening is to add back the heat (that is being lost through radiation out into space) either by using a hair drier or dew heaters. For this reason I have just made dew heaters for all my bits of kit as I got fed up with having to stop imaging on the few clear moonless nights available because 'Niagara Falls' had turned points of starlight into fuzz balls. I suspect your 'observatory enclosure' will increase the time before the dew point is reached but if the relative humidity of the air in the observatory is high and in reality it will be similar to ambient external RH, condensation will eventually form on bits of kit that have a surface temperatures equal or lower than the dew point temperature. I've rambled on for a bit - sorry - old consultants never die they just ramble on for a bit more. best regards from George 'moist' in Lowestoft next the Sea.

We had the electrical storm directly overhead in Lowestoft. A second after a tremendous lightning flash the Sun from the West created a wonderfully bright rainbow in contrast with the black 'back-lit' clouds in the East. Spectacular! I do hope you are all safe in your tents at Kelling? best regards George

Nicely bonkers mate! I manage to fill my 'down time' with similar eccentricities and my wife has been used to it for forty-six years, you have to admire their fortitude! best regards from George In Lowestoft

Hi Gina It's raining on one side of my house whilst I have bright sunshine on the other and I don't have a big house! I can be simultaneously optimistic and pessimistic - the wonders of living next the sea. regards George 'damp in Lowestoft'

Feeling quite 'chipper' today! Many of my little 'summer' projects have been completed and seem to work. First - my bathroom extract system has been installed without me once falling off the ladder or putting my foot through the bathroom ceiling, second - I'm now producing tasty pizza and bread from my DIY wood-fired bread oven without upsetting my neighbours and third I've constructed four battery powered 'dew zappers' for camera lenses and scope objectives. The following is proof: - 'Dew zapper' on the Canon EFS 18-55mm lens worked for just over 2 hours, allowing star trails and a time-lapse movie to be made, and thus exceeding the design parameters for the heater and battery. Many thanks to Alan Sheehan B.E on IceInSpace for his excellent article and Excel Spreadsheet relating to building 'dew zappers'. Thanks to Alan I could concentrate on the difficult bits including burning my fingers with a soldering iron and 'wrinkling up' the duct tape. http://www.iceinspace.com.au/63-292-0-0-1-0.html

Today, I made my first prototype 'dew zapper' for a Canon efs 18-55 lens. Powered by a 9volt battery rubber band attached to the insulation. Not a pretty piece of engineering but quite cost effective. (My daughter in law said it looked like an electrically powered toilet roll). A moist night here on the east coast, so I was pleased that it kept the dew at bay for the length of the trial (two hours). Moon very bright in the backyard so a good night for experimentation. Will make more zappers tomorrow for different bits of glass but to the same/similar design - now I know it works. Night all