Dew heater for the 10 inch Meade.

[+Graham]

 

Thought I would start this post today so you can see what I intend to make.

 

You can now get a dew heater for Celestron SCT's that are built into the corrector plate holding ring.

These are not available for the Meade SCT's so I am going to build my own for my 10 inch Meade SCT.

 

Here is how I am going to do it.

 

I have a large Aluminium ring left over from a Solar cell I made for the University of Singapore Astro department's new Celestron C11.

 

 

I also have a spare collector plate ring for my Meade.

 

 

I will manufacture a new ring from the Aluminium with a groove cut in the rear face to hold a ring of resistors thus providing the heat direct onto the corrector plate.  

 

More to follow as I will have to use the large Colchester Lathe at work as my Lathe here does not have a big enough chuck to hold this ring.

[+Ibbo]

I've started something again 🤣🤣🤣

[+Graham]

You have that Steve.

[+RonC]

Sounds interesting Graham. If anybody can do it, you can!

[+Graham]

 

I took some time out at work today to make the new retaining ring.

 

The front.

 

 

The groove for the resisters to sit in.

 

 

The back.

 

 

Just waiting for Amazon to deliver the resistors and I can put it together.

[Clive]

After fitting the resistors will you be infilling the groove with thermally conductive material to ensure good heat transfer to the ring?

[+Graham]

1 hour ago, Clive said:

After fitting the resistors will you be infilling the groove with thermally conductive material to ensure good heat transfer to the ring?

 

That is my intension Clive Yes.

 

Ring of resistors.

Unfortunately the Shrink wrap I brought home from work is just too small to go over the resistors.

Will have to get the next size up tomorrow.

 

I have now sprayed it Black ready for the final assembly and fitting tomorrow.

 

[+Ibbo]

Looks good it should do the business.

[+Graham]

I have a big thank you to give out to Clive.

He did the calculations on this and advised me that the Wattage output in this configuration was going to be too low for such a large scope.

I did test it and he was absolutely right, the Aluminium was dispersing the heat faster that the resistors were producing it.

Clive has come up with the configuration of two sets of seven resistors wired up in parallel which will give me 17 watts of heat.

So tomorrow I will split this ring in half and run a positive and a negative to the cut ends thus giving me a parallel wiring configuration.

This is going to save me one hell of a lot of work as I had worked out another way to do it which involved a lot more wiring.

So a massive thanks once again to Clive.

Watch this space for a full update on how it works.

[+Graham]

This morning I reconfigured the wiring to split the resistors into 2 banks of 7 wired up in parallel.

I gave it a test run and measured it was drawing 1.2 amps at 14 volts, the heat output was incredible. .

Happy with the test I stripped it down and filled the base of the groove with heat transfer grease.

After reassembly I fitted it to the Meade.

The heater is plugged into my dew heater controller as I doubt it will need to run at full power for long.

Cannot wait to test it out for real.

Roll on a clear night.

 

This is the new Dew heater ring in its home.

 

Edited September 3, 2022 by Graham

[BAZ]

That was an outstanding effort, from conception to finish it can be measured in hours! Also what brilliant colaberation from all, so it got done right first time too.

Edited September 3, 2022 by BAZ
Carp grammar!

[+Streetbob]

That’s brilliant.

[+Glafnazur]

Fantastic stuff Graham, well done 👍