Dew shields fo Newtonian OTAs - do they work ??

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Dew shields fo Newtonian OTAs - do they work ??

Postby reddenning » Sat Jun 23, 2018 2:20 am

I saw an ad on ebay the other day from someone advertising a Skywatcher 200mm Skyliner scope which also included a wrap round dew shield (non heated variety). I must admit that I've always assumed that a dew shield on an open tube Newtonian would be a complete waste of time since the mirrors would already be protected to maximum effectiveness inside the tube. Adding effectively an additional short length of tube in the form of a dew shield would not add much further benefit. I use dew shields on my cassegrain and refractor scopes but have never thought to add one to an open tube reflector. Does anyone have any views on the effectiveness of doing this?

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Re: Dew shields fo Newtonian OTAs - do they work ??

Postby Aratus » Sat Jun 23, 2018 6:08 pm

I agree with you. I can't think of any additional benefit to the mirror that might arise from extending the tube on a newtonian reflector. Either there is some benefit that escapes me, or someone is trying to flog a useless accessory!
I use an 11" reflector (Celestron CPC 1100) and a 3" refractor, (Sky-Watcher ST80) mounted on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI 120MM, ZWO ASI1600MC and Canon 1300D for imaging.
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