Resistor size for dew heater

[blinky]

Hi folks,

 

i I want to make a dew heater out of resistors for my telrad and my secondary of my new 300p dob. Just wondering how many ways of heat I need to generate for each of these devices...... I was thinking a failure 0.5w for the telrad and a couple for the secondary?

[mapstar]

Check out this site

http://www.iceinspace.com.au/63-292-0-0-1-0.html

May help 

[blinky]

Hmmm..... Yeah, thanks for that, was kind of hoping I could get somebody who has already done this to tell me how many watts of heat I need on the Telrad and Secondary

[mapstar]

Apologies

Try this for the telrad 

https://stargazerslounge.com/topic/42946-simple-telrad-dew-heater/

I'll have a look for the secondary heater later