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Equipment Discussions >> ATM, Optics and DIY Forum

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ischua
Under the Radar
*****

Reged: 07/17/08

Loc: Below Snow Plop, N Y
Eyepiece box heater new
      #5606961 - 01/05/13 04:58 PM

I was thinking about heating my eyepiece box to keep the eyepieces warm.
I have a hundred feet of roof heating cable plus hundreds of 1/2watt 330ohm resistors to play with.
How big of a pad would I need to make or should I snake something around base of eyepieces?
I also have a old heater strip from a 8in SCT I could glue to the inside if that would work.
How much warmth is enough in a box ? Any ideas or thoughts
Will be used with a DewBuster controller.


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Dick Jacobson
scholastic sledgehammer


Reged: 12/22/06

Loc: Plymouth, Minnesota, USA
Re: Eyepiece box heater new [Re: ischua]
      #5607207 - 01/05/13 07:56 PM

Have you considered just throwing a chemical hand warmer into the box?

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MessiToM
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Huntingdon PA
Re: Eyepiece box heater new [Re: Dick Jacobson]
      #5607295 - 01/05/13 09:00 PM

I can find the wattage of my kendric box heater out......

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dan_h
Carpal Tunnel


Reged: 12/10/07

Re: Eyepiece box heater new [Re: ischua]
      #5607304 - 01/05/13 09:07 PM

An aluminun box radiates a lot of heat when under a clear sky. I throw a padded blanket over mine and use handwarmers inside it to kept it cozy.

A wooden box has some natural insulation so may not need the blanket.

Depending on the size of the box, it's construction, and how cold it is outside, I would think you may want 2watts up to as much as 10 watts or more. Since you plan on using the dew buster, why not build for 10 watts and set the buster as needed to keep things warm. In a closed box that is insulated, 10 watts is a lot of heat.

dan


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MessiToM
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Huntingdon PA
Re: Eyepiece box heater new [Re: dan_h]
      #5607417 - 01/05/13 10:31 PM

Just checked. My Kendrick box heater is 10watts......

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lbsgville
sage


Reged: 06/15/10

Loc: Florida
Re: Eyepiece box heater new [Re: MessiToM]
      #5607972 - 01/06/13 09:48 AM

I used an old heating pad, like you would use on your back. I have my eyepieces in the aluminum tool case (briefcase style) that I got at one of the big box do it yourself stores. I spliced the wire and mounted a plug in the side of the box so I could just unplug the wire from the side of the box. I don't have any pics but could take some if anyone wants to see. It works very well.

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ischua
Under the Radar
*****

Reged: 07/17/08

Loc: Below Snow Plop, N Y
Re: Eyepiece box heater new [Re: lbsgville]
      #5608293 - 01/06/13 12:50 PM

The heating pad is great=simple but no 110 power available
so 12v. Not being in direct contact with the eyepieces I would be relying on radiant heat. I can build a 6"x4"pad underneath the eyepieces with all heat going up (approximately 4 or 5 watts max ) The dew strip I have would wrap around the ID of the box and has a rating of 25watts but would heat from the sides of the box. I'm more worried about how much is enough or am I over thinking?


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lbsgville
sage


Reged: 06/15/10

Loc: Florida
Re: Eyepiece box heater new [Re: ischua]
      #5608454 - 01/06/13 01:59 PM

Not having 110 is a problem at one of my dark sites. When I made my case I lived one hour from Chiefland FL and was going to Chiefland Astronomy Village for all my long term viewing and had access to 110. I didn't think about you not having it. What ever you come up with I think it may require at least two strips and its own power supply.

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k9yr
super member
*****

Reged: 05/21/08

Loc: Far North suburbs of Chicago
Re: Eyepiece box heater new [Re: lbsgville]
      #5609500 - 01/07/13 12:03 AM

I use a 12Vdc car seat heating pad. I keep my eyepiece box near the back of my SUV and the is a 12V outlet I can plug the cord into.

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BSJ
Pooh-Bah
*****

Reged: 12/22/08

Loc: Grand Isle, VT
Re: Eyepiece box heater new [Re: k9yr]
      #5613232 - 01/09/13 07:52 AM

Here's what I use in my small case. http://www.amazon.com/gp/product/B004ZJOE2M/ref=oh_details_o08_s00_i00

For me, the 1 star review was a bonus!


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gonzosc1
sage


Reged: 11/08/12

Loc: South Carolina
Re: Eyepiece box heater new [Re: BSJ]
      #5614003 - 01/09/13 04:16 PM

just an idea, how about a small pelitier element. like they use in small 12volt coolers. one side cools and the other heats. so mount it in the lid reverse or heat side in, ad small heat sink with cpu fan on top of it to move the air around the case. only down side I can see would be the frost build up on the outside element. may not be bad but don't know for sure..

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Gene7
scholastic sledgehammer


Reged: 06/10/10

Loc: Mid Ohio, USA
Re: Eyepiece box heater [Re: gonzosc1]
      #5614532 - 01/09/13 09:22 PM

I would make it self contained with one or two of the new #18650 Lithium batteries inside to also get heat from the battery. 4 volt cells will hold charge for about a year. Heat from power is exactly 100.00% efficient, so I would drive some LEDs to get light and heat. Would keep box small, air tight, 2 inch packed premium fine fiberglass. Gene

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Mike Lynch
sage
*****

Reged: 04/07/06

Re: Eyepiece box heater new [Re: Gene7]
      #5614567 - 01/09/13 09:48 PM

I'll second---or is that THIRD---the disposable chemical hand-warmers. I open one and toss it in the EP / accessory box. I put the lid down but don't lock it, and I can forget about dew throughout an observing session.

And, man, we get some DEW in Central Kentucky! (Probably like much of the central part of the U.S.)

Mike Lynch
Frankfort KY USA


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ischua
Under the Radar
*****

Reged: 07/17/08

Loc: Below Snow Plop, N Y
Re: Eyepiece box heater new [Re: Mike Lynch]
      #5617813 - 01/11/13 07:12 PM

I was able to scavenge elements from a bag sealer today.
12in long rated 85w 120v. I don't know if it can work with 12v without overloading/heating the wiring. Time to play!!


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propelller fan
member


Reged: 08/08/09

Loc: PNW...the wet side
Re: Eyepiece box heater new [Re: ischua]
      #5620740 - 01/13/13 12:56 PM

It should be workable.12 in long rated for 85w at 120v should give you 8.5 watts at 12 VDC. Even though it is rated for AC power, the heater element is not an inductive/capacitive load, so you can use ohm law, to calculate power, without having to take reactance into account.
Good luck!


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propelller fan
member


Reged: 08/08/09

Loc: PNW...the wet side
Re: Eyepiece box heater new [Re: propelller fan]
      #5620777 - 01/13/13 01:14 PM

One more thing about the heater element. It is almost certainly made of nichrome and can not be soldered. Instead of soldering, you'll need to use another way, such as crimping, to make a good electrical connection

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Gene7
scholastic sledgehammer


Reged: 06/10/10

Loc: Mid Ohio, USA
Re: Eyepiece box heater new [Re: propelller fan]
      #5621305 - 01/13/13 05:39 PM

Mike;
Sorry Mike, but your 85 Watt element (at 120V) will only operate at about 1 watt when driven at 12V. Again and again Astro Based people's electrical advice is just astonishing!
I would use oversize 10 watt ceramic resisters instead and mix in some LEDs to give some free light.


Should you want to solder Nichrome wire use hard silver solder and an alum based flux. Must use a small propane torch for this higher melt solder. Only buy from a welding supply outlet. Hardware stores ONLY sell junk hard solder. Gene


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don clement
Vendor (Clement Focuser)


Reged: 02/02/11

Loc: Running Springs, California
Re: Eyepiece box heater new [Re: Gene7]
      #5622065 - 01/14/13 02:32 AM

I believe only a small wattage would be needed for an insulated eyepiece box perhaps less than 10 watts. Nichrome wire would not be necessary as has been stated canít be easily soldered. If it were me, I would use a chain of easily obtained (I believe Radio Shack still sells small wattage resistors) small wattage resistors connected in series and/or parallel to obtain the resistance needed for the supply used e.g. 12V. Resistors can usually be easily soldered. Just make sure the wattage used for each individual resistor is less than that of each individual resistorís stated wattage rating. For this application it doesnít really matter type the resistor is (i.e. ceramic, metal film, carbon film, etc) as long as the wattage for each is kept at or under the stated wattage.

Don Clement


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gpelf
sage


Reged: 12/28/11

Loc: Kentucky
Re: Eyepiece box heater new [Re: don clement]
      #5622424 - 01/14/13 10:29 AM

Gene7,,,,+1 On 12v works out to .85w

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