Dew control for widefield lenses

[iceman]

I have a dew heater I can use on one camera, but on the other camera what can I use for dew control?

I remember something about hand warmer heater things from camping stores?

Exactly what are they, how much are they, and how long do they stay hot for?

How do you wrap it around the lens, and does it impact focus etc?

Cheers

[Phil Hart]

alex cherney put me onto the new packs first, after previously not having much luck with the gel type warmers which didn't last long at all.

the new ones are a dry powder, quite light weight with a claimed heat time of 8-12 hours. they only cost a few dollars.. a lot of chemists have them now and i've also seen them in aussie disposals. they're not reusable though.

i find they take a very long time to activate.. about half an hour and they need a lot of shaking and flexing to work air through the mixture. sometimes i also think that when they're left on the lens they don't work as well as their intended use next to the body where they keep getting moved around which helps keep air moving through the mixture. alex seems to have had reasonable success with them though.

eg.
http://www.hotteeze.com.au/products/hotteeze-regular-1p

pack of ten for $22.95 or check out your chemist etc. i think the exact same product gets marketed/packaged under many different brand names now.

cheers
Phil

[iceman]

Thanks Phil - I'll check out the local chemist.

[sebastion]

I have been using the 'wild country' chemical hand warmers with film lenses.
i stock up on them from rays outdoors (they only sell them in winter) they cost 1.50 each and are good for 8 hours.
i found that it is best to open them approx 15minutes before use and keep them in a pocket. then set f stop and focus, attach with rubber band to the topside of the lens, check focus then dangle a sock or something to insulate from cold air. (they dont work great on cold metal or plastic surfaces with out insulation)
The heat does not seem to affect the image or the focus during exposure.
i've attached an image, temp was 1 degree that night.

[iceman]

Thanks for the extra info Sebastian. I ordered a pack of 10 from the online shop that Phil linked - I hope they get here before next Thursday :)

I'll probably visit the chemist on the weekend too, to grab some extras (if they sell them) just in case.

[silv]

Hey There,

what was your experience with those Hotteeze heat pads?

I am off to get a 10-pack now. Will report back. :)
My camera lens drowned yesterday evening between 6 and 8.30pm ...

Is dew collection more intense during those early evening hours, I wonder?
Google .....

[iceman]

I didn't have success with the first one I used. I think the dew was just toooo heavy.

But I've only tried it once. I ordered a box of 'little hotties hand warmers' which I plan to take to the kimberley with me, but I haven't tried them yet.

Be keen to hear your experience.

[jjjnettie]

wow, you should be able to get a box of 40 pair ( x2 =80 ) hand warmers for around $25 off Amazon.
I'm thinking of going this way for the secondary of the RC.

These nifty usb heated gloves, with the removable element have me thinking though. For $5.80, you get 2 powered heaters with quite fine leads.

[Ryderscope]

Mike,

I use the Kendrik dew heating system with the dual channel (four output) controller. This gives me four dew control heating strips to use. There are a number of heating strips available and I use two types, ones which are designed for the 2" eyepieces and larger ones which are suitable for refractor OTAs.

I find that the heating strips designed for the 2" eyepieces work fine on the lens of the camera. By wrapping it around the lens before focusing this seems to work fine. With the controller supporting four dew heating strips I have enough for the camera lens, the front of the guidescope, the finder scope and one spare. The controller takes a 12v input with the standard car cigarette lighter plug.

Link to the Kendrick site showing the dual channel controller is here:

http://www.kendrickastro.com/astro/dew_controllers.html#StandardDualCh annel

The link to the information on the heating strips is here:

http://www.kendrickastro.com/astro/dew_premierheaters.html

Only cautionary note is that they do consume a reasonable amount of power so a good size battery is in order. I have a 18AH gel cell battery I use in the field and a back up in case I need it.

Hope this helps.
R

[silv]

5 hours outside yesterday with Hotteeze (http://www.hotteeze.co.nz/) on a sock wrapped around my camera lens using a rubber band.


the camera body and scope were dripping.

NO, I repeat, no dew on the lens.


:prey2:

[silv]

addition:
the Hotteeze was a used one!
I had used it 10 days ago, approximately, back then for 2 hours.
Afterwards, wrapped sock and hootteeze in a thick plastic zipper bag and suck out the air before closing.

Taking it out, yesterday, it warmed up again!
And did it's thing for 5 hours.

[Shano592]

Same as Rodney, here.

One for the EP, one for the finderscope, one for the front of the SCT, and the fourth one is used to power the lightbox.

They run all night on a standard-duty car battery, which also powers the laptop and the SCT.