Eyeball-Fogged Occulars?
I store my eyepiece case out in the observatory, which is handy, but on particularly humid evenings the cold eyepiece glass fogs much more readily.
I decided to add a little bit of electric heat to the case to keep the eyepieces a few degrees warmer. It should also have the desirable side-effect of lowering the humidity inside the case.
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Here's the eyepiece case at the start. The floor of the middle compartment is also raised, allowing further storage underneath.
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| All three trays removed. |
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I've chosen DewNot heater strips as my source of heat. These are their 1.25" eyepiece versions, good for 3.1w each.
But there's precious little room under the eyepiece racks, and their cloth covers are rather bulky.
| Original strip. |
Fabric covers removed. |
Re-wraped in heat-shrink tubing. |
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| The wires are sadly coax, which makes them a bit harder to deal with. The wire on the right has had the grounding wires gathered in preparation for heat-shrinking. |
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| And, both with a bit of heat-shrink tubing. |
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| Soldering the wires to the power plug. |
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| Here are the heater strips wired in and double-stick taped to the walls. |
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| The power jack on the back of the case. |
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| The finished result, loaded for bear. |
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Retrospective
In hindsight, I wish I had gone with slightly longer strips (something around 5w each).
I haven't had any issues with fogging yet, but tests have shown that the center compartment reaches a temp delta of only 8°F over ambient (although the eyepiece compartments probably show gradients on the order of 15°F at the inside edges down to 8°F at the outside). Still, I'd have been happier with a bit larger delta. |
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