After carrying out a lot of mods to my 12"LB over the last two years, I'd thought I was done but........... with a few lost nights to the dreaded dew, I knew that it was time for a secondary heater.
Now the one recommended for the LB's wraps around the sec holder, (and works well) its only drawback is that it uses a lot more power than the conventional heaters (having to heat the holder & mirror) attached to the back of the secondary.
So I decided that it was time for a project.
I bought the Astrosystems DG-1 heater.
Since I powered the rest of my heaters and fan through my 12V system, I opted for the same for this.
The most difficult part was removing the mirror from the holder,(I think they use a very strong glue at G.S.O.) you must gently lever it out (this takes a bit of time and patience) both the holder and the back of the mirror are cleaned with Metho.
After marking the position of the heater on the mirror, two holes have to be made into the holder. To keep wires from fraying over time I inserted grommets into the holes.
The heater is mounted on the mirror using Automotive Silicon. The heater was also sealed around the edge of the circuit board to prevent heat loss.
Then came the installation of the mirror, three small blobs of silicon would gently hold the mirror. To prevent further loss of heat I packed the inside of the holder with cotton balls.
After allowing to cure overnight, the holder is reattached to the spider.
From one hole comes the L.E.D. (This lets you know when the heater is on)
and the external sensor. The other is for the leads to the power supply.
I ran the power wires over the spider. I drilled a hole in the U.T.A. and down to a plug.
This was then fed down the (inside) of the truss and off to the switch box and power supply.
For a non standard job it went off very well (I didn't curse once
)
Result? Works brilliantly!!
I'd like to thank Chris (Omaroo) Dick Everett (M.A.S. member) and Jay Scheurle (CN member) for their invaluable advice and help.