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Anyone know where I can get a 9.25SCT Dew Shield at a reasonable price


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Seems to be a national shortage of 9.25 SCT (for a Celestron) Dew Shields - I know that you can make them but I would rather have a "proper" one.

I've seen one at £63 - seems a lot to me - I was thinking more in terms of about £30 or so.

Peter  :sad:

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You can't beat camping mat. It has a high insultating value and very low tenedency towards dew formation. But will a passive system be enough? Generally folks use heated systems on SCTs.

Olly

Absolutely this.

Plus you can make it a tad bigger so you can pull it over the heater tape. That way the heater tape isn't trying to heat the sky.

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Hi Peter, I have used camping mat material for many years with no problems. Just make it about 1 1/2 half times the diameter long, and this should keep any dew off the optics on a SCT. Also if you hit it in the dark !! you will not hurt yourself, have been there myself. Good luck with the project. John.

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Hi Peter, I have used camping mat material for many years with no problems. Just make it about 1 1/2 half times the diameter long, and this should keep any dew off the optics on a SCT. Also if you hit it in the dark !! you will not hurt yourself, have been there myself. Good luck with the project. John.

How thick was the mat - they come in different thicknesses. I saw one on E Bay which is 4mm thick - is that ok?

Peter

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Certainly try a dew shield, but be prepared to bite the bullet and go for heaters.  My C9.25 has been useless this winter without the heaters.  I don't reckon it has lasted more than ten minutes before starting to fog up.  It may be better now we're starting to warm up a little, but it hardly got below freezing here at all this winter.

James

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I have the AstroZap dewshied as well, but as James said without a heater you can pretty much forget it. I remember when I first bought my C9.25 I just bought a shield on its own. Well my first time out everything seemed ok, but within an hour or so the scope was pretty much unusable because of the dew that had formed on the front of it. Large SCT's are renowned for fogging up. On my old 127 SLT Mak I only needed to use a shield, but for the C9.25 it is mandatory for a heater as well. I use an Astrozap heatertape and controller. Works a treat now. No more calling it a day on my session early because I can't see anything. I can stay out until the bitter end now. I'll suffer from the elements before the scope will now.

Edited by M4lcs67
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I have the AstroZap dewshied as well, but as James said without a heater you can pretty much forget it. I remember when I first bought my C9.25 I just bought a shield on its own. Well my first time out everything seemed ok, but within an hour or so the scope was pretty much unusable because of the dew that had formed on the front of it. Large SCT's are renowned for fogging up. On my old 127 SLT Mak I only needed to use a shield, but for the C9.25 it is mandatory for a heater as well. I use an Astrozap heatertape and controller. Works a treat now. No more calling it a day on my session early because I can't see anything. I can stay out until the bitter end now. I'll suffer from the elements before the scope will now.

My experience exactly parallels this.  My 127 Mak would go for ages with just a dew shield.  I was shocked at how fast the C9.25 dewed up by comparison.

James

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My C11 can dew up in the time it takes to tweak the collimation. A dewstrap and a dewshield is mandatory on these things. I've even programmed a "Corrector Plate Demist" park position in EQMOD so if it does mist up again I can park it in the proper position to give it a blast with dry air from my obsy dehumidifier! :grin:

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Peter I started with the non heated dew shield for my CPC800 and it was not a success, since buying the asro zap heated dew shield- dew problems have completely been eliminated..

Having read this I have ordered one. Thanks

Peter

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