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There's another thing you can do - find a site where dew is NOT a problem.
Dew and astro do not need to go hand in hand. The location of professional observatories give us all the clues we need to find dew free locations:
* Don't set up on grassy fields. These seem like a good idea, but turf expires a lot of water during the night, and guess what forms - dew.
* Don't set up in valleys. Dew and fog are denser than the surrounding air, so they will settle into lower altitudes. Remember those lovely pics of fog filled valleys with exposed ridge tops? Set up on the ridge tops, not in the valley.
* Try to avoid agricultural land. This land usually means wet soil. Crop farms, dairy, horse breeders, piggeries, etc. All of these mean water, water everywhere, with rich moisture laden soils and a lot of turf.
* Rocky and sandy ground is best. Water drains quickly from these areas. The ultimate is a ridge top/plateau with a rocky/sandy ground. Fog settles down into the valley, a gentle breeze is never really far off from higher altitudes so dew is much less likely to form, and the altitude means less dense air, improving sky transparency and helping keep light pollution trapped to lower levels in the sky.
Trees are not such a problem as turf. A clearing that's surrounded by trees is brilliant as the trees act as a wind break and this can mean the difference between a cold but tolerable night and a night where the wind freezes you to the bone. If the clearing is poor sandy soil with parched grass, excellent.
We don't give much thought to where we set up beyond "Yep, this open grassy field will do". And you could just be signing up to a world of pain with dew. And many astro clubs are just as guilty for not giving enough thought to this with selecting their dark sky sites, and their dark sites are nothing more than dew magnets, and so reduced sky transparency. Give some more thought to where you set up, what the topography is, the surrounding vegetation, the surrounding land use, etc, and you may identify sites that will leave you dew free or the best chance at reducing it and the problems involved with dealing with it. I have dew mitigation measures on my scopes, but I only ever use them when I visit locations other than my normal dark sky sites. This weekend I went to one of my dark sites, and no dew formed on my scope. Yet on the drive home I saw everything else was soaked. Only power requirement I had was enough juice to power my torch.
Now you have to think about a hut, bringing enough juice not just for the mount and camera, but the huge amount of juice to deal with dew, and then packing water soaked gear, AND stopping water getting into your electrics! If you had given a bit more thought to where you set up, you may have been able to greatly reduced the impact of dew and the power and effort required to deal with it, or even avoided dew altogether.
Alex.
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