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Dew Shield

Steve1976

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Steve1976

Steve1976

Posted
Posted

Hi guys and girls!

Can anyone give me some advice on making a good dew shield? Also is a dew shield enough or will I need to give my scope the old hairdryer treament from time to time? I'm living in Ukraine at the moment and it is kind off wet and miserable a lot of the time (think Scotland only much worse!)

Thanks in advance

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russ

russ

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I always use one of the camping bed rolls, cut it too size. In the UK they cost a few quid (£3-5), so a very cheap option. Also bought a roll of Velcro from a hardware shop and ran it down where the two ends join. But my first few attempts were held together with electrical tape.

My location suffers with severe dew problems. I find a dew shield never does the job alone. I always need active measures to counter it. Heated dew band and the dew shield are good combo.

Russ

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Merlin66

Merlin66

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Which telescope??

I also use the camping mat... found one with a black side and a blue side ( sexy!) length should be about x1.5 the aperture ( for SCT's) allow about 50mm to sit on the OTA.

I used contact adhesive on the joint edge... a sharp scalpel knife, a metal straight edge, a bit of care and you'll get a good result.

( I made one for my 6" Cometracker back in 1985 and it's still going strong)

Ken

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russ

russ

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The heated dew band for my 8" SCT cost £25 and a further £12 for the straight through controller that plugs in the 12v Powertank. There are variable controllers available where you can adjust the power depending on the conditions. They start around £45.

Russ

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acey

acey

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Anything will work as long as it doesn't get soggy with dew and/or sag into the light path. You want the shield to be 2-3 times the aperture of the scope. It works by shielding radiated heat from the optics so all that matters is that the dewshield shades your glass from the sky - thermal insulation of the dewshield material is irrelevant, stiffness and durability are what matter. The interior should be matt black so as not to reflect ambient light into the tube. I use camping mat and velcro on my 12-inch but with smaller scopes I've managed with cardboard and elastic.

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Bizibilder

Bizibilder

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I just did a quick "glue test" on a couple of pieces of Lidl exercise matting. On the left is superglue (Loctite from Tesco's) and on the right (with the pencil between) is Thixofix contact adhesive. Both were applied exactly to instructions ie the Thixofix was left for 10 mins to dry before the bits were put together. The samples were then pulled apart.

Result - For BOTH the glue bond was stronger than the mat ie the mat gave way and tore rather than the bond. Purely subjectivly - The superglue had "welded" the two pieces and showed no sign at all of giving way, The contact adhesive gave a bond that was more flexible and apparently not so strong you can see where the material has come away on both sides of the joint.

I suppose you could use either for a dew shield's construction, personally I would go with the superglue as it is cheaper and easy to obtain.

post-17157-133877427521_thumb.jpg

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