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First dew heater completed

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#1 Hook

Hook

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Posted 17 August 2019 - 04:44 AM

So I have completed the primary mirror dew heater.

 

Nichrome wire in silver tape, black velour stitched cloth. I had trouble finding out how the bobbin fitted correctly lol.gif but a utube video helped.

 

Tested with 12v dc, and at full 12v it worked just right. Very pleased with the outcome. Just the secondary and wiring of control box to go.

 

dh1.jpg

 

dh3.jpg

 

dh2.jpg

 

dh4.jpg


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#2 scottmm2012

scottmm2012

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Posted 17 August 2019 - 06:14 AM

Looks good.  Specifics?  I'll be jumping into this as well, but for a much smaller astrophotography set up.

What guage nichrome?  What was your total wattage for the band?

 

I thought about wrapping the nichrome around old venetian blind slats.  Wonder if they would be too hot and melt (I could insulate first with heavy duty duct tape)?  Obviously not interested in using the old metal ones.



#3 Hook

Hook

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Posted 17 August 2019 - 11:03 AM

Looks good.  Specifics?  I'll be jumping into this as well, but for a much smaller astrophotography set up.

What guage nichrome?  What was your total wattage for the band?

 

I thought about wrapping the nichrome around old venetian blind slats.  Wonder if they would be too hot and melt (I could insulate first with heavy duty duct tape)?  Obviously not interested in using the old metal ones.

Hi.

In all honesty it is far easier than all the internet sites I visited during my research. I read about lengths of certain guages of nichrome with certain voltages, too much power.....too little power, it was mind-numbing at times, but I gathered enough info to know what was needed at minimum. So I purchased a 240-12vdc power supply.......from China.....8amp. I got 2 guages of nichrome, .4mm and .25mm. I had some pwm's here and a couple of temp units to stop/start heat flow. I got some silver duct tape and some black velour cloth.......it had to match the colour of my scope..grin.gif .

 

I tested both nichrome guages first, just used a piece of wood to lay them on. The .4 heated up with just 5v, and took the full 12v, but never went red-hot, but still too hot to grab. It reached 100 with the laser gun, that was 58 inches, enough to go round the scope twice, but I just bent it over halfway and brought it back so I could get the 2 feed wires together. I then tested the thinner one......waste of time, no heat at all with same distance.

 

I then put the .4 on the silver tape and tested again, leaving it at full 12v for a long time. No burning or smouldering of tape, so I put another piece on top to sandwich them together, (after folding the 2 first edges onto the wire).......and tested again. All sweet.

 

Then I cut and used the sewing machine for final looks, with velcro to hold it round the scope.

 

I wrapped the nichrome around the 2 power wires and soldered the power wires as the nichrome requires too much heat for soldering, but it worked fine, then heat-shrinked them.

 

Nice bit of heat radiating off it, and with the auto temp relays I can just set the temp I want inside the scope and leave it to do its thing.

 

Just have to work out how I want to heat the secondary without getting anything showing....but I'll get there.

 

Just get yourself some material to go over the duct tape, and use sticky-backed velcro to hold the ends together.. I did not insulate the part facing outwards, tbh I doubt it helps that much when outside, but some people do, so that's your choice.




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