Sgt.Pepper Posted May 13, 2011 Share Posted May 13, 2011 Hi, Can anyone tell me what length I need to make a dewshield for a 10" Dobsonian please? Is there a correct length per size of scope for dew shields? Link to comment Share on other sites More sharing options...
John Posted May 13, 2011 Share Posted May 13, 2011 I've heard that the recommended length is twice the diameter of the primary mirror. Mine (bought) projects about 12" above the top of the tube of my 10" newtonian and seems to work well enough.Dew is not a problem for me but stray light is - the main function of my shield is as a light shield. Link to comment Share on other sites More sharing options...
Sgt.Pepper Posted May 14, 2011 Author Share Posted May 14, 2011 John, Thanks for your advice. I have a problem with dew and light I will make one this weekend, and see how it goes. Cheers! Link to comment Share on other sites More sharing options...
NGC 1502 Posted May 14, 2011 Share Posted May 14, 2011 It's often said that a dewshield should be twice the length of the aperture.With SCTs, Maks & refractors, thats probably a good idea. But with a Newtonianwe are not trying to protect a large piece of glass pointing at the sky.The Newtonian secondary is much smaller, is some distance down the tube,and facing the other way. So I think that shorter is ok. It does help to combatstray light, but I made mine to help with occasional dewing of the secondaryon very damp nights.Best regards, Ed. Link to comment Share on other sites More sharing options...
MissMessier Posted May 14, 2011 Share Posted May 14, 2011 I made my dew shield from black camping mat and velcro. It does the job fine for stray light and dew. It's double the length of the diameter of the primary Link to comment Share on other sites More sharing options...
Adz Posted May 14, 2011 Share Posted May 14, 2011 My dob with a dew shield if it is any helphttp://stargazerslounge.com/equipment-reviews/140240-skywatcher-skyliner-200p-unboxing-building-some-add-ons.html Link to comment Share on other sites More sharing options...
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