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Dew Heater Strips with No Controller?

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#1 cloudswimmer

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Posted 16 February 2019 - 02:57 PM

Hey guys, so living here in So.Cal. and doing astronomy in the desert at places like Anza, Joshua Tree, Mt. Laguna, Mt. Pinos, etc. I've never had a dew issue, however now that I'm playing around and practicing astrophotography from my driveway in coastal Orange County (Irvine) I'm getting dew on my refractor and guidescope objectives .. so I'm thinking of getting a couple Astrozap heater strips .. but do I really need a controller? I'll just be plugging everything into a garage AC outlet via a DC/AC converter .. so I'm not concerned with power drain .. but is there anything else I should be wary of like the strips creating heat currents that might degrade image quality? Astrozap sells the kit thats just a female RCA jack on one end and cigarette lighter plug on the other, plus they give you an RCA splitter cable so you can run two strips .. I'm thinking of just getting that as again its only really when I'm at home during peak winter months that dew is even an issue .. bad idea? Yay or Nay?  Thanks for any advice.

 

Chris



#2 petert913

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Posted 16 February 2019 - 03:09 PM

Check these out.  Battery operated with no wires

 

http://www.tech2000astronomy.com/zap/



#3 bill5wjw

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Posted 16 February 2019 - 03:50 PM

Cloudswimmer, what you described from Astrozap is similar to the setup I use. Connect directly to my 12vdc source-no controller required. I wrap a strip around the main objective lens on the imaging refractor as well as the guide refractor. Good for the night.


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#4 PXR-5

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Posted 16 February 2019 - 03:52 PM

Check these out. Battery operated with no wires

http://www.tech2000astronomy.com/zap/


Pretty cool ;)

#5 cloudswimmer

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Posted 16 February 2019 - 08:00 PM

Cloudswimmer, what you described from Astrozap is similar to the setup I use. Connect directly to my 12vdc source-no controller required. I wrap a strip around the main objective lens on the imaging refractor as well as the guide refractor. Good for the night.

So are those strips just warm to the touch or do they actually get hot? 



#6 Michael Covington

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Posted 16 February 2019 - 08:40 PM

Just warm to the touch.

 

What I would do, if I had no controller, is turn them on for a minute and off for a few minutes, repeatedly.



#7 GlennLeDrew

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Posted 16 February 2019 - 11:11 PM

If you wish to use heaters designed for use with controllers, but sans controller, be aware that they're typically 'over'-rated in terms of current draw. I once measured a heater (an 'off brand' I've long forgotten) for an 8-9.25" SCT that consumed a frightful 37 Watts! I find that with a dew shield installed, such a scope does fine with about 5W of mean power draw.

 

For a typical controller duty cycle in the 50-ish per cent range, and assuming 12V operation, powering at 12V * 0.707 = 8.5V would result in the same 1/2 power draw as a 50% duty cycle. Voltage-selectable power supplies offering settings for 7.5V and 9V would be suitable. Make sure the unit can supply sufficient current! At least a full amp is a wise minimum, with 2A+ being better. Don't worry about polarity; heaters are simple resistors that care not for electron flow direction. ;)

 

The figure of 0.707 comes from the fact that power scales as the square of the voltage. 0.707 is the inverse of root two, or 1.414. Voltage reduced to 0.707 the former value reduces power draw to 1/2; increasing to 1.414 times the former value doubles the power consumption.

 

If you wanted to consume only 1/4 the power, run at 1/2 the designed-for voltage, or 6V (versus 12V.)

 

For shorter focal length systems like camera lenses, 'over-heating' is less a concern than for lengthier telescopes.


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#8 Dreams4000

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Posted 17 February 2019 - 12:39 AM

I've used these on my rigs with no problems.  They have a built in low/high power switch and plug direct into 12v. (none of the rca challenges)   I just have them hooked into some Talentcell 12v batteries to keep it all mobile and easy.  The red/green light for the high/low power is a little bright, but nothing some electrical tape can't fix if it bugs too much. :)

 

https://smile.amazon...e?ie=UTF8&psc=1

 

The seller is also quite responsive to questions.  


Edited by Dreams4000, 17 February 2019 - 12:41 AM.


#9 bill5wjw

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Posted 17 February 2019 - 07:52 AM

I use the heaters from DEW-Not.com. They draw minimal current, and they are well made.



#10 cloudswimmer

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Posted 17 February 2019 - 10:32 AM

I use the heaters from DEW-Not.com. They draw minimal current, and they are well made.

Yes I had it narrowed down to either Dew-Not Strips or Astrozap Strips. A professional observatory operator friend of mine uses Dew-Nots on his own personal rigs and that swayed me in that direction, plus I think the Dew-Nots look cleaner with no logo on em .. but I ultimately chose the Astrozaps as the cord is on the outside of the velcro which potentially gives me more cord routing options, plus I've talked with Joe at Astrozap quite a bit and he's always available and cool should anything go haywire. Do you use a controller with your Dew-Nots?


Edited by cloudswimmer, 17 February 2019 - 12:42 PM.


#11 cloudswimmer

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Posted 17 February 2019 - 12:36 PM

If you wish to use heaters designed for use with controllers, but sans controller, be aware that they're typically 'over'-rated in terms of current draw. I once measured a heater (an 'off brand' I've long forgotten) for an 8-9.25" SCT that consumed a frightful 37 Watts! I find that with a dew shield installed, such a scope does fine with about 5W of mean power draw.

 

For a typical controller duty cycle in the 50-ish per cent range, and assuming 12V operation, powering at 12V * 0.707 = 8.5V would result in the same 1/2 power draw as a 50% duty cycle. Voltage-selectable power supplies offering settings for 7.5V and 9V would be suitable. Make sure the unit can supply sufficient current! At least a full amp is a wise minimum, with 2A+ being better. Don't worry about polarity; heaters are simple resistors that care not for electron flow direction. wink.gif

 

The figure of 0.707 comes from the fact that power scales as the square of the voltage. 0.707 is the inverse of root two, or 1.414. Voltage reduced to 0.707 the former value reduces power draw to 1/2; increasing to 1.414 times the former value doubles the power consumption.

 

If you wanted to consume only 1/4 the power, run at 1/2 the designed-for voltage, or 6V (versus 12V.)

 

For shorter focal length systems like camera lenses, 'over-heating' is less a concern than for lengthier telescopes.

You lost me in the math there Glen confused1.gif lol. Could you summarize that for a mathematically challenged astronomy brother tongue2.gif Again I'm not concerned about power draw as I'd only need the dew strips when I'm at home in light polluted So.Cal. practicing with my software/hardware in the front yard. For serious astrophotography I'll be out in the desert where dew has never been an issue for me. My only concern running the Astrozap dew strips direct is if that can hurt the objective on my 4" refractor or 50mm guidescope. Thanks waytogo.gif



#12 Michael Covington

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Posted 17 February 2019 - 01:18 PM

If you want to run dew heaters without the controllers, look for a 5-volt power supply that can deliver a couple of amps.  (Such things may come with older backup disks and other computer peripherals.)  Running a 12-volt heater on 5 volts will keep the temperature moderate.


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#13 Cancington42

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Posted 17 February 2019 - 06:20 PM

a controller isn’t really necessary, but can help in warmer and humid conditions to lower the temp as it’s not required to have full power in temps above 10 derees C. During the winter months i have it set to max power and works. I ended up just getting the appropriate potentiometer to the amperage rating of the dew heater and soldered it inline. It cost 10$ including shipping, so compared to most controllers over 100$, it could save you money and still get the job don.



#14 mikerepp

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Posted 19 February 2019 - 11:54 AM

Try one of these for a controller, cheap, reliable been using these for years and wont break the bank.

 

led dimmer.JPG

 

 


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#15 cloudswimmer

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Posted 19 February 2019 - 12:11 PM

Try one of these for a controller, cheap, reliable been using these for years and wont break the bank.

 

attachicon.gif led dimmer.JPG

Cool .. are there RCA jacks on the back, or do you have to cut the jack plugs off your heater strips and wire them in?



#16 mikerepp

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Posted 19 February 2019 - 08:10 PM

they have screw terminals but easy to wire in RCA jacks.  I have a simple setup using these just mounted to a board and wired to a small box.  The box has the RCA jacks and switches for control.  

IMG_1806.JPG

 

You can remove the board and the pot from the case and mount the guts in any case you wish.



#17 cloudswimmer

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Posted 21 February 2019 - 01:40 PM

they have screw terminals but easy to wire in RCA jacks.  I have a simple setup using these just mounted to a board and wired to a small box.  The box has the RCA jacks and switches for control.  

 

 

You can remove the board and the pot from the case and mount the guts in any case you wish.

Thats very cool Mike waytogo.gif I'm not much of a DIY'er when it comes to electronics .. give me a hand fed lathe or mill and I'm at home .. but electronics yikes blush.gif lol. Think I'm just going to get the Astrozap controller and be done with it, but thanks for sharing that pic .. always enjoy seeing DIY pics waytogo.gif



#18 CharlesC

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Posted 21 February 2019 - 02:24 PM

Buy a dew controller for $2.56 here.  It even comes with a wireless remote.

If it expires search for others on ebay using "12V Wire RF Wireless Remote Switch Controller Dimmer for Mini LED Strip Light"

 

Or just try pointing a window fan at your OTA from ten feet away.  That will stop dew.


Edited by CharlesC, 21 February 2019 - 02:26 PM.



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