Is dew seasonal ??

[Skipper Billy]

Hello.

I am in my first season of using a telescope and the last 3 months have been a write off due to the weather.

Last night was the first time I have been outside into the small hours using a telescope and I was shocked at the dew - everything was absolutely dripping.

Is this less of a problem in the late spring, Summer and early autumn or is it pretty much the same all year round ??? 

If its a perennial problem I will have to look at heater strips etc !!

Just taken a few things outside now (18.05) to be ready and they are already covered in dew!!

[AstroJOE]

Not sure its exclusive to Autumn and Winter but its certainly 10 times worse! I only tend to use heater strips during the colder/damper months. Dew shield alone seems to work for me the rest of the year and the eyepieces down tend to fog up as much either from body heat during Spring/Summer. Worth investing in heater strips and/or heated dew shield though in my view as you never know what the weather will throw at you!

[cotterless45]

yep, autumn and spring, when temperatures can change quickly. this leads to dewhumidity. A dew shield and shroud will keep it at bay, followed by a hair drier, followed by retreat. Dew heaters should be on from the start of the session. not breathing on the ep and keeping them in a nice clean warm pocket helps,

Nick.

[Space Dragon]

It is a problem that can drive you mad, especially in Scotland where the humidity tends to be a bit higher.

I have a selection of heaters and long dew shields to combat it but still, winter nights are the worst.

A bit of a breeze will generally keep it at bay.

 In summer it hardly gets dark enough to take a scope out. And you'll have the midges to contend with as well.

Autumn has been the choice season the last two years, winter has been a write off. 

One [the only] good thing about dew is it can stop you staying out too late and being a wreck the next day.

[Paul73]

+1 for the clean warm pockets for eyepieces. Don't know what I will do when I have more than 4 eyepieces (only 4 pockets in my coat). Unfortunatally, the same trick doesn't work on a troublesome secondary.

@Nick - Autumn seems to have dragged on a bit!!!! My scope has been dripping for most of the winter. When it hasn't been sopping wet, it has been covered in ice.

So, in summary, we have about 3 weeks (what we call summer in the UK) where dew won't be an issue?

Time to invest in one of those camping hair dryers.

Looking forward to warmer observing.

Paul

[chiltonstar]

Dew - yup, seasonal like Vivaldi (all 4 seasons). Worse in Spring and Autumn though, as stated above.

Chris

[Charic]

Heater strips work, dew shields also. The longer it takes to cool the optics,  the less the dew should form on its surface. Dew will form when a surface cools below the dew point of the air next to it.  I dont thinks its seasonal,  but Its a catch 22 ? You don't want heat inside the OTA or in the optics due to the thermal disturbances caused when viewing at higher magnifications, and if its too cool, dew can form. Reflectors, due to the mirror being at the base of the tube, should already have a natural dew shield, the tube that it sits in, however folk still extend their OTA's with foam dew shields made from sleeping bag underlay mats from any camping store. 

[davefrance]

You may be able to predict bad dew days/nights by looking at the due point temperature http://www.weatheronline.co.uk/weather/maps/current?LANG=en&CONT=ukuk&LAND=UK&REGION&SORT=2&UD=0&INT=24&TYP=taupunkt&ART=karte&RUBRIK=akt&DATE=--&CEL=C&SI=mph.

The dew point is where the air cannot continue to hold all its water and dew starts to form. The dew temperature will vary day to day and location to location.

[andyman]

And try to observe away from lakes or any water source where the dewing will be ten times worse.try to observe in the open if possible where any breeze will help with dewing