Monitoring Temp and Humidity in the Observatory

I bought a temperature/humidity sensor from ebay recently.
It can be connected to the USB port of a PC and the readings recorded on the PC.
Below is an example of the results obtained over the last few days:



Interesting to see how the temp. and hum. can vary over the course of a couple of days.

Michael.

Have just a manual one myself Michael, it's all down to what air mass is over us on any given day. Best scenario for us in Ireland is usually a clearance from a cold front bringing in less humid, although cooler air usually from the west or sometimes the north. A warm front is just cloudy and sometimes damp weather.

We live in a country with such changeable weather (thanks atlantic jet stream) that it's so hard to pin down when there are good and bad months for astronomy during the year.

In general, I have found that as for visual and astrophotgrapy, humidity at night below 80% is acceptable, though sometimes it's hard to get even that in Ireland.

Keith..

I've noticed that even with 100% humidity indicated on my Kendrick that I still get good results... Come to think of it, humidity rarely drops below the 90 mark.

Michael - did you measure it with the dopen open or closed? If closed, do you think it will cause a problem for your equipment? Enough to have to get a dehumidifier?

I've updated the chart above with some more data - a refresh of the page should reload it.

Dave,

Is that reading 100% power applied by the dew controller or 100% air humidity?

These measurements are with the door closed.
I have a dehumidifier but only need most at certain times of the year.
The counterweights, mount and sometimes the scope can have dew on them.

One of the things to note from the charts is how close the air temperature gets to the dew point. They are closest at the early hours of the morning when the air is warming up and the humidity is falling.
However the metal in the scope and particularly the mount will take longer to heat up. Therefore their temperature will still be a couple of degrees colder than the surrounding air. This will put them below the dew point and hey presto, condensation will form on the metal.

At least I now know that I can set the dew humidifier on a timer switch from say 6-11am. This should minimise dew problems and minimise electricity costs.

Michael.

Actually, pretty much both... The Kendrick displays air temp, optics temp, air humidity and power it is pumping to the dew strap. With 100% humidity, its normally pumping 100% power to the strap. I can afford to do that now I've got the kendrick powered by a 12VDC transformer rather than a battery.

Its actually the norm that humidity would be well above 90 at night. I've no recollection of it being lower - though I don't check TBH. The Kendrick does produce a log alright - I could analyse it...