humidity

[Ally8446]

I'm planning an observing session tomorrow night so naturally I checked astro panel. It says 0% chance of rain, good seeing but 98% humidity. Can this level of moisture in any way harm our beloved equipment ?

[RichieP]

Things may get a bit dewy , but no harm will come if you let things dry off after you bring them indoors.

More worrying is that, if you have light polution, moisture in the air will make it so much worse.

[Ally8446]

Thanks for the reply Richie. Was worried about ep's, Telrad etc. I'll just enjoy the night.

Clear skies

Ally

[m37]

Wow, 98%? Isn't that the same as Japan?!!!

[Ally8446]

98% did seem really high but I'm only quoting astro panel. Not very impressed with that app at the moment I have to say.

[m37]

I was amazed so I had to check but it totally is around 98% in the uk loads of the time. That's like the jungle in Burma. Phew.

[Tonys]

I think it depends on the temperature, at least as far as comfort is concerned. With 98% humidity the air at tropical temperatures holds a lot more water than it typically does for us. I'm not sure if this means more dewing under tropical skies though.

[umadog]

I think it depends on the temperature, at least as far as comfort is concerned. With 98% humidity the air at tropical temperatures holds a lot more water than it typically does for us. I'm not sure if this means more dewing under tropical skies though.

I think the amount of dewing depends upon the water content (as you say) and the rate of temperature drop. So when it falls below the dew point (http://en.wikipedia.org/wiki/Dew_point) you get condensation. That's why black parts exposed to the night sky dew first (because they can quickly cool to even below ambient temperature by radiative cooling). Once or twice I've been outside on a humid night when the temperature dropped quickly and it's astonishing how rapidly everything get soaked. Almost as though it rained without raining -- really weird.