Colin's Astronomy Pages

Power box
New Heating Element

Contents

As this is quite a large project, I've decided to split this project into several pages. Each page dealing with a different aspect of the project.

Having used my old dew heater for a couple of years, I've found that it works quite well. However, I've also started thinking about the effect that all the insulation is having. With a layer of heat strink, and some inulation tape there's quite a bit of stuff for the heat to get through before getting to the scope. Even then, one is gets to the scope, it's still got to penetrate through the outside of the OTA to get to the corrector plate. All in all, that's along way.

I've seen several other websites showing ideas for heating elements, two of them seem to strike more of a cord that the others. The first site suggested using copper tube, then threading several high wattage resisters through the tube. The second suggests using resistance wire, wrapped around the outside of the OTA and held tight by a spring.

I was thinking about this and like the idea of using copper tube to conduct the heat evently around the corrector plate. Also being placed inside the lip of the scope, it's practically invisible and delivers the heat right on target. But the website for talking about a 10" LX200. So I needed to adapt this for the LX90. The answer came from the second site. Combine the copper tube with the resistance wire and you'll have an element that's easier to contruct and works efficiently.

Now I wanted to think small, so I got some 4.7mm copper tube. Which I bent to shape, this was accomplish by using the lip on my focusing aid as a guide. This left a ring that was oversized. Then with a little persuasion, I forced this into the lip of the OTA to pull the ring in a little tighter.

Next job was to place the resistance wire into the copper tube. But I didn't want direct contact, as this could short out. So I cut the resistance wire to length leaving some extra so that the wire will hook over the edge of the OTa, allow connection to the supply wire.

Next I threaded the wire into some heat shrink. Then connected the ends of the wire to a 12v battery. This will give you some idea of the power that this heating element will have. The wire got hot enough to cause the heat shrink to er, well, shrink! And that was with not extra help.

I then threaded this into the copper tube and attached some speaker wire to the ends of the resistance wire. Also I added a little more heat shrink to cover the bare wires. This time I used a hair drier to do the shrinking. As the other end of the speaker wire is a 3.5mm jack plug which connected into the power box.

Finally I sprayed the copper pipe matt black, and took the picture above. You can see the heating element around the outside of the corrector place housing. It's almost invisible in black. I think this has a really nice finish.

Power box New Heating Element

Power box
New Heating Element