Eyepiece Heaters

[Stickboy (Phil)]

Hi all, The other night I had dew all over my SCT and I am using a dew shield.

I did a search for dew heater and found that everyone was talking about heaters and controllers for the corrector plate but not eyepieces. Should I by a eyepiece heater at the same time or are they ineffective if the eyepieces are changed around a bit

Phil

[Allan_L (Allan)]

If you use the one eyepiece for a prolonged period, then yes an eyepiece heater can be of benefit.
Other measures such as putting the end cap on when not observing also help.
If the conditions necessitate, a couple of eyepieces when not in use, can be kept in your pockets to keep them warm and above dew point.

Even with a dew shield, I found it necessary on occasions to use a dew heater for the corrector plate.

My 12 volt heater controller can manage 4 independent heater straps.

I also would use one for my finder scope.

But that's just what works for me.

[Stickboy (Phil)]

Thank's Allan the eyepieces in the pocket sounds like a great idea. I think I will get a heater for the spotting scope as you recommended. I will be going west of Tamworth in September 4 to 8 deg over night. I want to be prepared just in case

Phil

[multiweb (Marc)]

Have you tried a littlehotties hand warmer stuck in a sock around the focuser. That should give you 8 to 18hrs of heat depending on the size. I use them on my lenses when imaging all the time. Great passive heating. No power requirements. You can order a pack of 80 on eBay for $40 or there about or get them from Costco fro $20 for 40 I think.

[Stickboy (Phil)]

Interesting idea Marc. I thought that a hand warmer would be to localized and place to much heat to one area. But I do like the price and the convenience of a little pack

Phil

[Meru (Michael)]

Hi Phil,

How's your skills with electronics? It's very easy (and cheap) to make a simple dew heater from nichrome wire, there's a few write ups on the net. I start with a simple single heater which needs no controllers, and now just made myself a 4ch controller and can make the straps to suit anything I want (for your mount, telescope, finderscope - you can customise the shape and power to whatever you like ). This cost me 1/10th of buying the same thing from the shops! If you regularly swap the EPs then you could even build a little heated holder box where you keep your EPs in, so that way they stay warm and when you take them out they won't dew for a while.

I'm happy to build you one if you like, or just give advice if you wanna do your own send me a PM if you wish

Cheers

[mental4astro (Alexander)]

There is one thing we often forget about eyepieces and heating straps we loop around them when in the focuser - metal conducts heat, glass does not.

So, you wrap the heater around the metal casing of your eyepiece, that you've slotted into a metal focuser that is fixed onto a metal tube. Net result, you've got a fantastic heat sink to suck the life straight out of your battery, and your eyepiece still fogs up.

A heat strap should not be used to heat up a cold eyepiece. It isn't designed for this. And if your eyepiece is a 1kg lump of glass, you are dreaming if the heating strap will have any effect.

Heat straps for eyepieces should be used to help maintain the heat that is already in a warm eyepiece. Some of the posts below talk about heating your eyepiece in your pocket, which is part of the solution. In a cold environment, you should look at keeping all your eyepieces warm during the whole night, not just while in your pocket. A heat pouch just won't do much to heat the core of a 500g eyepiece, and nothing to a 1kg lump. But if the heat is already in the eyepiece from the start, the heat pouch and heating strap will perform best for you.

There are many ways people have devised to heat their eyepiece case. Some wire a series of resistors into their case. Others put a few of these hand heat pouches into their case. Me, I've gone real high tech - a hot water bottle in a cosy, and a couple of towels over the lot. The heating strap I use then does a fabulous job for me over the three hours of a sketch I'm doing.

Remember, as soon as you put the eyepiece in the focuser, it will be losing a bucket load of heat through it. So to make the most of heating straps and whatever you have in your pocket, the best solution is to have the eyepieces warm from the start. Glass does not conduct heat well, so don't solely rely on momentary heat solutions.

Mental.

[Stickboy (Phil)]

Meru, Building your own equipment is always the best way to go. If something happens in the field there is a chance that you can fix it and keep thing going. Thanks for the offer to contact you for help

Alexander, Great advice on keeping things warm for the entire night.

Phil

[Visionary (David)]

I love the idea of water bottles and hand warmers, lateral and cost effecive solutions. I have pondered on how Nth Amercan Astronomers manage under feet of snow. Not only are their eye pieces at risk, the genuine threat of frost bite must be a real issue. Though even in Oz there are country locations that fall well below freezing for the entire night. What are the strategies for when the mercurary plummets? Astronomy is very passive, your not exactly generating buckets o heat through exertion how do you stay safe and warm?

[Stickboy (Phil)]

David, I have been going to Manilla which is 45 mins N/W of Tamworth for years. Only a couple of times in winter and we ran the heater day and night. I am looking at some new jackets for my wife as she doesn't think that we will make the 2 weeks in a tent I was there last month and by the end of the trip it was getting cold. We would start the trip with the sleeping bags open then as the nights got colder we would zipped up the bags and pull the bag tight around our heads to keep warm and the poor dog even started to shiver. Last week I got the wife a new sleeping bag next is the jacket.

Phil

[The_bluester (Paul)]

I have found that the heater will keep my ES30 clear quite well, though it does need to be cranked up, as Alexander wrote, the EP body, tube and scope itself is a very effective heatsink.

I should arrange an eyepiece box heater, I wonder about a terrarium heater pad fitted under the pick and pluck foam. Something running off 12V would be ideal as I have that on hand via a PSU with about 6A capacity to spare.

The EP heater was the difference between being able to use my old Nagler 11mm and leaving it in the box, it dewed up even more readily than my SCT does.

[Akwestland (Andrew and Kim)]

I know next to nothing on this subject, but, how would a home brew heater pad work for this, these are the ones that people sit their "brew" barrels on to keep them at a constant temp. Could this be put under the foam in the EP box. The only down side is that i am unaware of being able to run them on 12V unless you use an inverter.

Meru, I may be interested on how you put this together for "next to nothing".

Cheers,
Andrew.

[Meru (Michael)]

Not a problem, send me a PM

[ZeroID (Brent)]

Originally Posted by Akwestland

I know next to nothing on this subject, but, how would a home brew heater pad work for this, these are the ones that people sit their "brew" barrels on to keep them at a constant temp. Could this be put under the foam in the EP box. The only down side is that i am unaware of being able to run them on 12V unless you use an inverter.

Meru, I may be interested on how you put this together for "next to nothing".

Cheers,
Andrew.

I'm using one wrapped around the 102mm Lunt but those things are 240 VAC, not 12 volt. I'm in an Ob close to the house so not a problem but obviously no good in the field. Inverters and the like are notoriously inefficient. If I was going to use mine I'd nick one of the wifes UPS's from work, charge it up and chuck in the back of the car. At 6 watts it would give about 20 hours runtime at least.
I've wrapped an old bath towel around the heater on the Lunt to reduce losses, bulldog clip secures it on. I've also thought about getting a couple more for an EP box and and also the SW 80 f11.

[Renato1 (Renato)]

My opinion - heaters and controllers obviously work and are the elegant solution, especially for imaging. But it's a complicated solution.

For plain visual observation, I use a far less complicated solution, namely a big battery pack and a 12 volt hair dryer. When the SCT and eyepiece and finderscope dew up - I apply the hairdryer every 15 minutes or so as required. This is not the best solution for viewing planets and double stars, but it is fine for Deep Sky objects.
Regards,
Renato

[AG Hybrid (Adrian)]

I have a dew strap for my eyepiece in the focuser. But, a hot water bottle wrapped in a towel in your eyepiece case is highly affective. The eyepiece absorb some of the heat and negates dew from forming all night. With a dew strap at providing just a little bit of extra warmth to maintain the heat, I promise you, you would will not have dew problems with eyepieces!

[Stickboy (Phil)]

Renato I don't think my neighbours would like a hairdryer running all night next to their house. I have to keep close to get away from the street lights.

Adrian I hope to get a heater for the EP box. But maybe a hot water bottle to start with.

I am going to go with the DewBuster controller. Has a good number of ports for the extra items and simple easy to use. But not so good with the Australian dollar at the moment

Phil

Edit - I had dew the other night but it didn't affect the scope or eyepieces, just my glasses when I put them on the table