Eyepiece case heater pad.

[The_bluester]

I thought this would be about the best place to ask this one.

Regularly through the winter I find that my EP case is sopping wet by the end of a nights of observing. I have a smallish pelican case with pick-and-pluck foam in it with holes pulled out for the eyepieces.

I was thinking that a small amount of heat in the case would be a good thing. I often need to leave the case open for some time (Days even) to ensure that all the moisture evaporates. Better to nip it in the bud if I can and prevent the case from dropping below the dew point to start with. It would also have the advantage of keeping the eyepieces a bit warmer as sometimes on really cool nights they tend dew up when first put into the scope and then clear as my EP heater warms them up.

I was thinking of as 12V heater pad that could be put under the foam in the case with an external power connection and potentially a potentiometer to give some adjustability to the amount of heat delivered. I was not thinking anything as costly as the likes of a Kendrick heater controller would be required for a case heater. I have as 240V bench power supply providing 12V for the gear when in use so battery power is not a problem. best options would be something that was "Just enough" so that it could simply be hooked up and let run flat out.

I am sure I would not be the first person to do something like this so I am hoping someone might be able to suggest a supplier for a suitable heater pad?

[glend]

Why not just put something over it to prevent dew settling inside the case. A piece of clear perspex, even a towel works.

[The_bluester]

There is that, but as much as anything else I would like to keep the EP's slightly above ambient when they are not in use.

I find I need to be really careful in the winter as if I have a beanie on (So a nice warm face) I find the EP can tend to immediately fog when I first go to use it, then clear a few minute later as the EP heater warms it. I need to keep my face way from the EP unless it feels like my nose is going to drop off with the cold! I would like to be able to go back to a balaclava in the really cold weather.

[LewisM]

I keep a baby bottle warmer strip in my EP case lid (remove the foam when in use). Keeps em toasty :)

When I am using EP's, I place a hand warmer chemical pack on the top side of the EP to keep it warm out of the case, held on with a rubber band. Well, i USED to until I got another EP heater strip this past week.

[mental4astro]

The solution I use is real high tech - a hot water bottle!

The hot water bottle is in a cosy. I put a towel over the EPs, the bottle on top, and then a blanket over the lot. The EPs warm up, and the heater strap I put onto the EP at the focuser doesn't need to labour much at all to maintain some heat in the eyepiece.

I've been doing this for several years now. I have never seen any effects of having warm eyepieces in the image in case you are wondering, with many, many hours spent sketching, hence observing, this way. But I am using an open truss dob. I have a 2l thermos of hot water with me. This is plenty for sub zero temperatures that we typically encounter here in Oz. This gives me 1 litre to start with, and enough for a change of water around midnight.

Any 12V solution will really chew through power. There is a lot of bulk that needs heating in any eyepiece case. I considered some type of 12V solution first up too, but the power requirements were ridiculous and ultimately not a practical observing solution. The hot water bottle is just easier. A few of my observing buddies have started using hot water bottles this way too. No foggy eyepieces, and many productive hours :)

Alex.

[Wavytone]

Hmmm.

Alex you've just reminded me of the one downside of my turret - the eyepieces did get so cold as to fog while up at Blackheath.

Might have to follow by example and make a heated eyepiece box with a hottie inside :)

[The_bluester]

In my case the power requirement should not be a bother, the heater is more of a convenience than anything else so if we happen to be away from home I am no worse off than now if I do not have it. When at home I have 240V within reach to keep as 12V bench supply going.

[AG Hybrid]

I agree the hot water bottle is very effective. Wrap it in a towel too so it doesn't straight up lose its heat rapidly to the cold air. It was a rookie mistake when I forgot to use it during our outing last weekend.

[Wavytone]

I have an eyepiece case with a fair bit of empty volume in the bottom. Ideas...

1. A plastic bottle or just a bag (fom a wine cask) full of hot water in the bottom, and a towel over that.

2. Insert a couple of Uniheat slow release heat packs.

3. Put a vent in the side that connects to a hairdryer. Close the lid and run hairdryer for a few minutes to warm everything up.

4. Eliminate the hairdryer and install a nichrome wire heater in the bottom, battery powered...

[The_bluester]

I think I would head direct to option 4. I don't really have much free space in the case to put heat packs or hot water bottles etc. A slimline heater of some sort underneath the padding would be the cleanest option.