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Showing results for tags 'condensation'.
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Hi all. I'm hoping for some advice on a subject which I know has had a lot of air time, but which I'm still wrestling with. Firsty, I know I get dew on my secondary mirror and it has wrecked many a DSO photgraphy session. I've fitted a home made heater, and this seems to fix it. It's insulated with neoprene, and runs at a very low wattage (about 0.4W) , so hopefully not too much turbulence. Next step is to do the same to the guide scope, which also mists up after about an hour, and then maybe the primary with a very low wattage. The main puzzle for me is this: Some folk say the mirrors are huge heat reserves, and take ages to cool down, during which time they cause turbulence. But other folk say the mirrors drop in temperature rapidly and go below the dew point, and then suffer condensation. I suspect theres some truth in both statements, but this doesnt simplify how to deal with it. Probably the main consideration is that the primary is much less ikely to suffer dew than the secondary, and so they have different problems and solutions. It would be easy to say that turbulence is in the eye of the beholder, but for sure when I'm focussing - using the camera and Live View with high screen mag - there appears to be turbulence aplenty even after an hour of cooling and before putting the secondary heater on. Of course this could be atmospheric, rather than tube currents. Rather than go through all my (muddy) thinking, can I just ask some direct questions please which relate to all this. 1. Is the small amount of heat on my secondary likely to cause any significant turbulence? 2. Is the turbulence that I see on the screen likely to be caused by the OTA? 3. I havent actually seen dew on the primary - but I've read that low grade condensation can affect the reflection. Is heating of the primary maybe just unneccesary? 4. If I heat the guidescope with a belt at about 2.5W, might this adversely affect the guiding property? 5. If I use an exhaust fan to cool the primary, is there any prospect that the air current will: a. increase dew on the primary and/or secondary by drawing in more damp air? b. reduce dew on the primary and/or secondary by evaporation? I'd be really grateful for any help with this. My next step is to wire up some kind of controller, and it would be useful to know what I'm likely to need to run before doing this. Many thanks
Hi All, Last night should have been great, clear skies and I've been looking forward to it since I bought my new scope. I set up early evening, just before sunset and waited for the stars to show. The problem started a couple of hours after viewing, condensation, eyepieces, corrector plate, even the glass on my Telrad. Even after wiping with a soft lens cleaner the problem soon returned, spoiling my viewing. Is there anything I can do to prevent this problem or at least reduce it ?? Corrector Plate ?? I think thats the name of it, its the glass in front of the Optical Tube. Please correct me if I'm wrong. Cheers All Pete
Just had quite a frustrating night trying to image Orion's Nebula. I got my reflector polar aligned and out nice and early to acclimatise. Sadly I didn't get very far, even at high exposure times I got no hints of the nebula. I brought my scope in and found that all the optics were covered in condensation, which I'm assuming is what's caused the problem. It's a cold, clear night in Hull, I'd say seeing was fairly good, perhaps minimally misty. I've done a bit of Googling and searching on this forum and found stuff on dew shields and heaters. I was wondering if people had any comments or advice on how to deal with condensation? Thanks guys!