What size "heated dew band" do i need?

[bcfcciderhead]

Measured the secondary mirror on my SW 200P Newt by wrapping a piece of string around it, the length of string then measures 8" (well good as).

But a little unsure as to what size dew heater i need to go around it.

I am on the right track with this is how you control the dew on a newt?.......heat the sec mirror?

Any help with what size i need would be great, i have a dew controller being made but thought i'l buy the heater, looking at the astro zap types.

Cheers

[andrew s]

It is not normal to wrap a heater a round a secondary as you will increase the central obstruction. More normal is to add a resistor or two behind it. - Andrew

[LukeSkywatcher]

If the scope is 200mm in diameter then thats the size of the dew heater strip to go for. I bought one for my 200mm SCT and it fits perfectly, you dont need to worry about the outside diameter because it sits just behind that. It does not sit at or near the secondary mirror...................it goes on the other end.

For my 8" sct, I bought one of each of these:

http://www.firstligh...ater-tapes.html

http://www.firstligh...controller.html

Stupid why they dont package both parts in one pack............because one cant work without the other.

[bcfcciderhead]

I thought the heated band goes on the secondary mirror on newts?

but on maks etc the band goes around the outside of the ota near the corrector plate?

[Islander]

If the scope is 200mm in diameter then thats the size of the dew heater strip to go for. I bought one for my 200mm SCT and it fits perfectly, you dont need to worry about the outside diameter because it sits just behind that. It does not sit at or near the secondary mirror...................it goes on the other end.

For my 8" sct, I bought one of each of these:

http://www.firstligh...ater-tapes.html

http://www.firstligh...controller.html

Stupid why they dont package both parts in one pack............because one cant work without the other.

He's talking about a Newtonian not an SCT - the heater fits directly onto the secondary not around the tube.

The heater I have for my dob just lays on the back of the secondary, The cable runs along one of the spider arms.

[faulksy]

as said heater bands are for cats only, peeps add resitors to the mirror on a newtonian

[bcfcciderhead]

Thanks islander, thought it did.

my plane is to buy the small 1.25" eyepiece band end fix it (like you said) to the back of the secondary mirror with the cable going along one of the spider vanes and out the tube.

if this could be done any better would like to here from you.

[bcfcciderhead]

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as said heater bands are for cats only, peeps add resitors to the mirror on a newtonian

my electronic skills are not the best so looking for an easy way out

Any links or info on how to do this would be most helpful

[Islander]

The secondary heater I have is just a length of heater wire (nichrome) in heat shrink tubing - you just curl it around the holder against the mirror glass.

Here's a link you might find useful if you can solder

http://www.dewbuster.com/heaters-330ohm_resistors.html