Dew and your Telescope

Today we have added a new map to the Viewing conditions for Sydney as well as adding it to the Clear Sky Chart. This new map shows the likelyhood of dew along the east coast of Australia as well as a zoomed in view of Sydney. When you look at the colors on the map or chart, blue will mean no chance of dew at that particular hour while yellow means you have a very good chance of dew forming so be prepared. Purple and any shades leading to blue are pretty safe too…. but monitor for dew if the color shows shades of brown or yellow.

What is dew?

Dew is pretty simply amospheric water vapour which condenses on objects such as your telescope and will occour when the temperature of your telescope falls below the dew point. The dew point is the temperature at which the water vapour condenses.

I remember the first time I experienced dew on my telescope while out in the field. It was about 10pm and I noticed that when I ran my hand along the telescope tube it was absolutely soaking with moisture. I looked through the red dot finder of the telescope and saw a lot of dew on that as well. You can imagine what I saw when I looked at the optics of the telescope.

So what should you do to protect yourself from dew?

If you see dew forming on the optics of your telescope, the number one thing you should never do is wipe the dew off with a cloth. If you have a car with a heater you can take the effected parts of your telescope and let your heater remove the dew via evaporation. If you do this, make sure you have all the optics uncovered and remove all caps. Otherwise, take the telescope and optics inside and let them dry off over a matter of hours.

Keep the dew away from any electronic equipment you have. For example the grass will become wet as a result of the dew and you probably don’t want cable connections lying in the wet grass. Keep an eye on your hand controllers too if you have a go-to telescope.

If the dew is really bad, you can protect your telescope by covering it with a cotton sheet.

You can also purchase dew heaters or dew shields for your telescope however these will not always be effective if the dew is bad.

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~ by sydneystargazers on April 6, 2010.

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