catman161 Posted January 29, 2012 Share Posted January 29, 2012 Hey everyone. After last nights meet teaching me that I need some sort of dew prevention system. I was wondering what would be the best solution for my SW 200p Dob? I saw Darren had a flexible dew shield on his 200p and the difference it made to the view last night was unbelievable. When I got home I had a look down the OTA and saw that my primary had turned into a swimming pool! So I reached for the other halfs hair dryer and that sorted it. Does anyone have experience with Astrozap dew heater tapes? Are they effective? Do you need one for the primary end of the OTA and one for the secondary? Any advice/thoughts much appreciated. Thanks Felix Link to comment Share on other sites More sharing options...
Guest Kheldar Posted January 29, 2012 Share Posted January 29, 2012 Camping foam + velcro has been all the dew protection I've ever needed Link to comment Share on other sites More sharing options...
Brantuk Posted January 29, 2012 Share Posted January 29, 2012 For a dob you need a dewshield in moist air - it's usually enough. It protects the secondary which is most prone to misting up. You can get special heater pads to stick on the back of the secondary if the shield doesn't fix the problem. The cable trails as thinly as poss across a spider arm (stuck on with black tape) and then to a power source (usually 12v battery pack). Google "secondary mirror heater pads". You can knock up a very effective dew shield with black camping mat for a coupla squids. The tailor made ones are expensive for what they are but do look good - popular makes for both items include Astrozap, Rigel, Kendrick, HitecAstro, B&C, and others (Nick from Altair recently put up some good ones in the traders section too - I'll be getting a 10" dewband from there) The primary mirror is usually ok - surprised yours was iffy - a fan behind it blowing air up the tube might help. Link to comment Share on other sites More sharing options...
catman161 Posted January 29, 2012 Author Share Posted January 29, 2012 Thanks for the advice guys. Regarding the primary I think it's because the OTA was literally covered in a layer of ice that was probably 2.5mm thick and then I put it in the car and was cold so blasted the car to boiling point with the heater I will look into perhaps manufacturing a dew shield from a camping mat! Felix Link to comment Share on other sites More sharing options...
Doc Posted January 29, 2012 Share Posted January 29, 2012 It is strange the primary iced up as it wasn't that cold last night. I would go for camping mat as this doubles as a stray light inhibitor and resistors on the back of your secondary joined up to a dew controller via a 12v battery. Link to comment Share on other sites More sharing options...
Rusty Strings Posted January 29, 2012 Share Posted January 29, 2012 I've never had dew on my 200p primary. I guess your dob must be a dew magnet Felix, apart from the outside of the tube, my scope was free of it last night Link to comment Share on other sites More sharing options...
glider Posted January 29, 2012 Share Posted January 29, 2012 Interesting feature on Kheldars new OTA is that the secondary and spider must be 9" down the OTA, whereas on the 200P it's practically right at the end. It provides a kind of built in dew shield. Link to comment Share on other sites More sharing options...
catman161 Posted January 29, 2012 Author Share Posted January 29, 2012 I've never had dew on my 200p primary. I guess your dob must be a dew magnet Felix, apart from the outside of the tube, my scope was free of it last night What?! Mine was covered in ice! Link to comment Share on other sites More sharing options...
Rusty Strings Posted January 29, 2012 Share Posted January 29, 2012 Wel,l mine was covered on the outside but clear on the inside Link to comment Share on other sites More sharing options...
Brantuk Posted January 29, 2012 Share Posted January 29, 2012 Fixed a couple of typos in my post - it now reads correctly. Link to comment Share on other sites More sharing options...
Guest Fluke Posted January 29, 2012 Share Posted January 29, 2012 As a cheapo option Rother Valley Optics recommended a home made cardboard hood for me. I didn't have any card around so used some 0.3m foil/vinyl I'd got from work instead attached using masking tape so not to mark my tube. So far it's done the trick! I can get a bit more vinyl for others FOC if anyone else fancies giving it a go Link to comment Share on other sites More sharing options...
Guest Fluke Posted January 29, 2012 Share Posted January 29, 2012 That should read 0.3mm by the way lol Link to comment Share on other sites More sharing options...
Daz Type-R Posted January 30, 2012 Share Posted January 30, 2012 Yeah the dew shield's are a must for us dob owners, by the end of Saturday night I had a good 2mm of ice on the outside of the OTA, but everything was fine inside. As mentioned above, you can make them yourself for next to nothing (like my Telrad dew shield) but I just thought £30 was next to nothing, so thought I would get the proper one. As another thought, when transporting my scope, I keep the car as cold as possible, and deffinatly no (or very little heat) on the way home. I also prop the mirror end up so it is higher than the open end, that way, if any moisture does form inside the OTA, it runs towards the open end, and not towards the primary mirror. Link to comment Share on other sites More sharing options...
Guest Eddy Posted January 30, 2012 Share Posted January 30, 2012 Daz, don't suppose you have a link to the shield you bought? Thinking of getting one myself. Mine had a tiny bit just on the inside on the edges, like around the top but there were no puddles Link to comment Share on other sites More sharing options...
Daz Type-R Posted January 30, 2012 Share Posted January 30, 2012 Here you go...... http://www.firstlightoptics.com/dew-prevention/astrozap-flexible-dew-shield.html The one for our scope (200P) is this one..... 8†LXD 75 SN: £31.00 For a bit more info to help the guys at FLO out, say you also need the one with the following code..... AZ107. That will fit a treat round our OTA, they sent me the AZ101 and it was massive! Link to comment Share on other sites More sharing options...
Guest Eddy Posted January 30, 2012 Share Posted January 30, 2012 Thanks Daz, Might get one ordered Link to comment Share on other sites More sharing options...
catman161 Posted January 30, 2012 Author Share Posted January 30, 2012 Here you go...... http://www.firstlightoptics.com/dew-prevention/astrozap-flexible-dew-shield.html The one for our scope (200P) is this one..... 8†LXD 75 SN: £31.00 For a bit more info to help the guys at FLO out, say you also need the one with the following code..... AZ107. That will fit a treat round our OTA, they sent me the AZ101 and it was massive! Awesome thanks Darren . Thanks for the pointers Re: travel home on cold nights, definitely will remember not to blast the car with heat in future!! Lol! Felix Link to comment Share on other sites More sharing options...
Guest wisewoman Posted February 5, 2012 Share Posted February 5, 2012 Ditto here - a £1 camping mat from poundland - cheapest dew shield ever Melissa Camping foam + velcro has been all the dew protection I've ever needed Link to comment Share on other sites More sharing options...
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