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FAQs...
Q: When I leave the heater strap units on the tube, like you said for extra-easy-portability, won't the battery snaps wear out when I connect and disconnect each time I go out?
A: No. These are MOLDED battery snaps very unlike the ones you are used to. Used in High-Reliability systems that we have produced over 20 years. They will take any punishment you might offer - and keep on clicking. Those snaps are made that way for such roughness, commonly used by industry and military for the same reasons. It's the 'good-stuff'. -Dave
Q: I have a 10" SCT. Will the Large unit 6-10" work on that?
A: THE SCOPE SIZE IS NOT THE TUBE SIZE! The tube is always a bit larger in diameter than your optic aperture. The large unit ZAP-LG straps around a maximum of 10" diameter tube. But you have a 10" aperture optic so the tube it rests in will be larger by at least 1/2". This size is the border of useful wattage delivered by one battery so you should use the X-Large method and get 2 ZAP-LG units. Then you have twice the power which is more appropriate for that extra large aperture... especially on an SCT telescope since those have no projecting cowling to protect the corrector plate from the sky radiant-sink (in the dynamical thermal sense of black-body absorber). -Dave
Q: OK I know this is kind of technical, but what is this thing actually doing?
A: The purpose is to introduce a limited and controllable caloric input into the direct circumfrential region of any optic lens, in a thermally conductive manner (transference), so as to keep the surface temperature of the outer-face of that lens just a fraction-of-a-degree above the air temperature that is at the molecular surface of that lense, simply to prevent the attachment-bonding which will ensue and produce fogging, the same way that rain droplets happen in the atmosphere (called condensate), but there are dynamics involved also in electrostatics and black-body emission and absorbtion... "Why is my table soaking-wet tonight but my telescope has no problem yet". It's like intoducing BTU's but that is all about how long it takes to completely melt a ton of ice so is not the proper measurement scale in thermodynamics to be applied here. Many methods of doing this for astronomical purposes have been applied from professional to mainstream advanced-amateur uses. ALL have been costly. Until now. -Dave
Q: How many watts do these give?
A: Each unit routs the watts needed according to the battery state and this is a complicated and dynamical system. How many watts do you need in Ohio, and how many in Antartica? What season is it? What time of night? What is the dew-point? What is the condensate coalescence of your glass? What coatings exist on the top-layer and what are their coalescence factors? How old is the coating? Hence we only can limit the answer with the unit maximum of 2.3 watts for any of the unit sizes. During use these Zap-On's will deliver everything they can and there is the unusual feature, quite unusual, they are able to suck-out every joul of capacity in your power supply if you allow them the time to do so - they are like The Terminator in the movie - they ABSOLUTELY WILL NOT STOP until the power supply goes to ZERO. And I do mean really really zero. Be aware of this and do not leave it connected to your vehicle battery if you use the 12V cord connection. -Dave
Q: Can this be used on composite-tube telescopes?
A: Yes. Actually that is an advantage since the lens cell you are heating is thermally de-coupled from the tube. Composits like carbon-fiber and fiberglass or even cardboard, have a much lower thermal conductivity than metal tubes so they will allow more heat to conduct into the lens. -Dave
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