Blower for de-fogging eps/secondary mirror

[markse68]

I’ve been contemplating building a diy blower to defog my ep as i’m finding if i take a break from observing i have to endure a period where the ep is fogged as it has cooled and the humidity is so high at the moment. Which is a bit of a pain. But I had a look around and it seems that we’re getting spoilt for choice on new high performance rechargeable blowers. There are a lot of generic computer duster blowers on amazon quite cheaply but a couple stood out- the Kica looks a really nice very high power blower that i’m sure would clear an ep fogging in seconds but at a price:

https://www.kica-tech.com/en/kica-jetfan

Then there’s a very compact unit from Nitecore - the blowerbaby , designed as a replacement for the rubber bulb blowers used for dusting lenses, but again at quite a price:

https://www.nitecore.co.uk/products/nitecore-blowerbaby.html

Anybody have any experience of these or similar? They’re not heated but I think a strong blast of air should clear fogging anyway? I guess putting the ep in a pocket to keep it a bit warmer would also work but i worry about pocket lint and dust creating worse problems…

Mark

 

[apaulo]

i just had a look on ebay, rechargeable hair drier 26 quid.  cheaper still put the e/p in your pocket with a handwarmer. clear by the time you blow your nose, wipe your eyes and stamp your feet, lol

[bosun21]

I just use a dew band on my finder and eyepieces.

[Don Pensack]

It has multiple uses:

https://www.opolar.com/products/2019-new-opolar-battery-operated-air-duster?currency=USD&variant=31955082051664&gclid=Cj0KCQiAveebBhD_ARIsAFaAvrGhr0QiwkIBOYZxmlCijifU_WqVr4SOqP0Urjx6JavhKqEwIdTSJPgaAsV8EALw_wcB

Something similar might be available in the UK.  Mine came from China directly.

As for inadvertent fogging of the eyepiece with your breath, I keep a folding Japanese fan in my pocket and it works great to evaporate the moisture.

You can find them easily on many websites.  It's called a sensu.  You can wave it vigorously and blow a lot of air at the eyepiece.

[markse68]

13 minutes ago, Don Pensack said:

Something similar might be available in the UK.  Mine came from China directly.

That looks like one of the more generic ones on Amazon Don- certainly looks up to the job of blowing dust. I guess part of my question is a physics one- will blowing cold saturated air at a cold eyepiece actually evaporate the fogging or does it need to heated? I think it will as blowing air on a wet hand cools by evaporation and from your description of the folded fan it does? 

Mark

[markse68]

1 hour ago, bosun21 said:

I just use a dew band on my finder and eyepieces.

Don’t really want wires and batteries and controllers and bands though- figured a small pocketable blower would solve the problem in a neater way

Mark

[markse68]

1 hour ago, apaulo said:

i just had a look on ebay, rechargeable hair drier 26 quid.  cheaper still put the e/p in your pocket with a handwarmer. clear by the time you blow your nose, wipe your eyes and stamp your feet, lol

Can’t imagine a £26 battery hairdryer would be very good quality- might work though thanks- will have a look. Don’t really want to put eps in pocket for reasons mentioned.

Mark

[Alien 13]

I have one of these for cleaning computer bits and keyboards, very powerful and because of the motor heat it does produce mildly warm air, might be a bit too strong for optics though as it can knock empty cans down from 12 foot away 😀

Alan

Edited November 20, 2022 by Alien 13

[markse68]

12 minutes ago, Alien 13 said:

I have one of these for cleaning computer bits and keyboards, very powerful and because of the motor heat it does produce mildly warm air, might be a bit too strong for optics though as it can knock empty cans down from 12 foot away 😀

Alan

That looks a beast! Brushless motor too- thanks- one of the better ones I think

Mark

[bosun21]

1 hour ago, markse68 said:

Don’t really want wires and batteries and controllers and bands though- figured a small pocketable blower would solve the problem in a neater way

Mark

I know what you mean but I tried a 12v fan blower and depending on how bad the dew actually is it soon builds back up and you will be repeating the process all night. I also found that I thought I was loosing clarity when perhaps i wasn’t. For myself a band wrapped neatly around my eyepiece removed all this. In the end if you go with a blower consider getting a heated one as it will increase the time gap between using it.

[Mike Q]

Fans may work depending on where you are.  Here in Ohio not so much, sort of like dew shields, sometimes they work sometimes they dont.   I use a dew bands on my OTA, finder and eyepieces.  Dew is a thing of the past.  

[Stephenstargazer]

As you are in UK ( not super humid) moving cool air is generally sufficient. Even a bulb blower for an eyepiece. @markse68 the Nitecore is made for camera stuff, usually safe and I note it has a filter. Good idea given the high air speed claimed ?

Understand why imagers need dew bands, but for visual it is an unwelcome extra. Except maybe with SC or Mak with large exposed corrector,  then you may have no choice. Also if you are an all night type of astronomer you will get below the dew point a lot.k

Edited November 21, 2022 by Stephenstargazer

[markse68]

Thanks Stephen, I will try a bulb blower next time i’m out- if that works it maybe all i need. I only just discovered the nitecore. They do look neat. They have a newer version with variable speed. Ridiculously expensive though like all nitecore gear! If it were half the price it’d still be an investment but i’d buy one. Now i’m thinking again about a diy solution using a low power centrifugal blower and resistors to warm the air a bit. 

Mark

[Louis D]

22 hours ago, markse68 said:

if i take a break from observing i have to endure a period where the ep is fogged as it has cooled and the humidity is so high at the moment.

What about simply covering the eyepiece with a cloth sleeve or similar to reduce radiative cooling when you step away?  You're saying it never dews up while you're at the eyepiece, correct?  That seems to indicate radiative cooling to the night sky as the culprit.  You could even keep the anti-dewing sleeve warmed with glove warmers when not in use.

[Stephenstargazer]

10 hours ago, markse68 said:

Thanks Stephen, I will try a bulb blower next time i’m out- if that works it maybe all i need.

I could not resist this one from Giotto.

[Don Pensack]

On 20/11/2022 at 10:20, markse68 said:

That looks like one of the more generic ones on Amazon Don- certainly looks up to the job of blowing dust. I guess part of my question is a physics one- will blowing cold saturated air at a cold eyepiece actually evaporate the fogging or does it need to heated? I think it will as blowing air on a wet hand cools by evaporation and from your description of the folded fan it does? 

Mark

Dew doesn't form in windy environments.  The simple act of blowing air evaporates any condensation.

I've accidentally fogged up an eyepiece on a night when my scope was sopping wet, and the small hand fan cleared the eyepiece in seconds.

Now, I do have to say that if dew is a problem on the secondary, it might be necessary to use a heater of some sort.  You can buy small 12V hair dryers (camping item, I'd guess),

and they work fine to evaporate condensation on secondary mirrors and eyepieces.  Your choice.

A mildly cold environment where you accidentally exhale on the eyepiece can be handled with a fan or unheated blower.

A seriously dewy environment like the dew shower I experienced in Australia will need heating.

[Don Pensack]

7 hours ago, Louis D said:

What about simply covering the eyepiece with a cloth sleeve or similar to reduce radiative cooling when you step away?  You're saying it never dews up while you're at the eyepiece, correct?  That seems to indicate radiative cooling to the night sky as the culprit.  You could even keep the anti-dewing sleeve warmed with glove warmers when not in use.

It sort of goes without saying that eyepieces should be capped if you step away from the scope.

[TheLookingGlass]

I use hand warmers, (the kind you shake to activate), with an elastic band on my eyepieces and 50mm RACI finder when it is dewy out.

Works great!

[TheLookingGlass]

18 hours ago, Stephenstargazer said:

I could not resist this one from Giotto.

I have that same blower bulb. Works a charm!

[Moonlit Knight]

I use a blub blower for eyepieces, works in seconds every time