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Lp filter misting


Frenchgow

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I recently bought an Idas lp filter to use in conjunction with my dslr and coma corrector on my Newton scope,sadly after about ten minutes of use the filter mists up and degrades the data I'm trying to gather,I leave the equipment to cool off for quite a while in my obshed before use, is there something I can do or magic substance I could use to alleviate this issue?

Regards Gary

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Hi Louise ,yes I have a dew shield almost the length of the scope 1m,I also have a fan at the primary mirror end ,

It doesn't seem to make any difference ,could it be that the air space between the coma corrector and the filter be the cause ? I'll maybe have a word with the guys at FLO where I bought it from , another expensive piece of kit sitting unused, hey ho that's the nature of the hobby I suppose,

Regards Gary

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Hi Louise ,yes I have a dew shield almost the length of the scope 1m,I also have a fan at the primary mirror end ,

It doesn't seem to make any difference ,could it be that the air space between the coma corrector and the filter be the cause ? I'll maybe have a word with the guys at FLO where I bought it from , another expensive piece of kit sitting unused, hey ho that's the nature of the hobby I suppose,

Regards Gary

Hi

Not sure what you mean by "air space between the coma corrector and the filter"? Have you tried without the fan running?

Louise

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Since you are using a Newtonian, dew shield is on one side, ventilator on the other, so those can not help you with fog on your filters...

If you use a 2" dew heater around the corrector and filter your problem will probably be solved...

Also: do you let things cool down separated? If the air that is caught in between your filter and corrector has high humidity and cools down it will reach dew point, the air cannot contain the moist anymore and condensates on the coldest surface, being your filter apparently.

Many dew-straps are available in any astro shop. You can make something yourself too with resistors. 

If you would like a 2,4 Watt heating (0,2 Amps), what  you need ± 16 1 K. Ohm 1/4 watt  resistors (brown/black/red). connect them parallel with ± 1 cm distance. Be sure to insulate them from your metal housing by taping them in between 2 layers of duct tape for example. Rap around your filter and connect the two leads on one side with your 12 V power supply and your foggyness is gone...

If you want more heat, use more of the same resistors, less visa versa.

Arithmatic:  Ohms Law:  A=V/R  and W=V.A

A= Amps; V= voltage; R= resistance; W= watts

Waldemar

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