Is it worth trying an anti fog treatment?

[JOC]

I wear spectacles and goggles for skiing.  I've also tried diving and worn a diving mask.  All these are prone to fogging up with water vapour.  As you may have read in my other thread I had a real problem with dew last night.  Do astronomers use any anti-fogging treatments on their eyepiece lenses as well as the heaters? 

For example, in diving they 'spit' into the mask rub it around and crudely wash out any excess - it does a surprisingly good job.  In skiing and optical glass you can buy various spray on treatments for the lenses.  The best I've used in this area is a small smidgen of washing up liquid rubbed over and it will literally polish to a shine and work all day.  Basically for large lenses anything capable of breaking down the surface tension on the water droplets seems effective in preventing misting up.  I know the area of glass on an eyepiece is not huge, but do astronomers use any similar treatments, what and do they work?

[laudropb]

I have never heard of anyone using anything like this. The coatings on eyepieces  have to be treated with care. The advice is never to poor/ spray with cleaning fluids directly on to the eyepiece. This is to prevent leakage into the inside. All cleaning fluids are applied sparingly on a microfibre or similar type of cloth. This makes me think that applying protective fluids directly is a no go.

[westmarch]

I would second what laudropb says.  Why don't you just pop your eyepiece into your pocket - it will quickly heat it up and disperse the fogging.

John

[JOC]

So eye pieces can be warm, but mirrors are best at ambient?  I thought everything needed to be cold like the outdoor environment.

[ollypenrice]

The simplest of all tricks near home is to have some warm towels ready on a radiator. If something fogs up, drape a warm towel over it. It will get you going again, but dewheaters are the only permanetnt solution.

Olly

[westmarch]

Hi,

The reason for cooling your primary mirror is that it is by far the largest and heaviest part of your telescope.  As a result it takes longest to cool down.  As it cools, it heats the air directly above it and these air currents are like looking through the rippling air above a hot road. 

Your eyepieces are however small by comparison and and so heat and cool quickly.  The disadvantage is that they fog up quickly, the advantage is that the fog and air currents disperse equally quickly.

John

[JOC]

Ah, OK John that helps and makes sense - then I shall still put the telescope outside in the afternoon before I think I will want to use it, but I'll leave the eyepieces inside, or perhaps in the porch until I am ready to go outside.  I like the idea of having a warm towel handy, a small electric blanket, might even be worth a try. 

[Waldemar]

why not just go for the simplest and proven method of dewcaps and -heaters?
If you use a good system with a sensor that is monitoring the outside temperature and the temperature of the dewcap, you will have no dew and no aircurrents caused by excess heat of  an uncontrolled dewheater.
I believe Kendrick was the first to bring them on the market.  I use a Kendrick Digifire 10 unit and have no problems whatsoever. (and I live in Holland... the wettest place on earth, if you ask me...)

Any chemical treatment could damage the coatings of your scopeglass on top of that it will add alayer which could influence performance

[JOC]

Waldemar a whole system to sort out the dew issue, wow!  It seems the skies the limit when it comes to what you can spend on this hobby - the scope cost me a fair bit, the mains cable more, the power bank, more, a couple of eyepieces, more, now it looks like I could make use of a dew control system and heaven help me I've been looking at the cost of UHC filters!!!  However, a dew system is probably the answer so I guess I'll start saving.

[Waldemar]

10 minutes ago, JOC said:

Waldemar a whole system to sort out the dew issue, wow!  It seems the skies the limit when it comes to what you can spend on this hobby - the scope cost me a fair bit, the mains cable more, the power bank, more, a couple of eyepieces, more, now it looks like I could make use of a dew control system and heaven help me I've been looking at the cost of UHC filters!!!  However, a dew system is probably the answer so I guess I'll start saving.

Yep, when diving into this hobby, or should I say addiction, there will be no time nor money for alcohol and wild women...  
and we did not even talk about imaging... just bottomless... 

[Waldemar]

1 hour ago, JOC said:

Ah, OK John that helps and makes sense - then I shall still put the telescope outside in the afternoon before I think I will want to use it, but I'll leave the eyepieces inside, or perhaps in the porch until I am ready to go outside.  I like the idea of having a warm towel handy, a small electric blanket, might even be worth a try. 

Putting your telescope outside while the sun still shines may be counterproductive... and be very carefull it does not accidentally point into the sun's path !!!

[JOC]

Because the air in the tube could warm up - yes?  That's worth thinking of in the summer, but it's been terribly cold outside over the last few weeks that I can't see it heating up at the moment, esp. as I've been taking it out after about 4pm when the sun has lost any winter intesity anyway.  I do watch the sun position though and always set it so that it faces where the sun has already moved on from - I also leave its little fabric tube 'hat' in place just in case.

[Dave In Vermont]

Agreed with above - don't go using any chemicals on your coated eyepieces, lenses, mirrors, etc!

You'd be "courting-a-disaster."

Dave

[JOC]

Okay, no chemicals - got it, so I need a physical solution - these heaters and shields are what I'll start to look at.  Thanks all. 

[John]

10 minutes ago, JOC said:

Okay, no chemicals - got it, so I need a physical solution - these heaters and shields are what I'll start to look at.  Thanks all. 

Dobs don't tend to suffer from dew as much as some designs. With your Skyliner Flextube I'd have thought a light shroud plus a dew shield at the top end would suffice ?

For eyepieces, just keep them a little warmer than the outside temp and they should be OK. I keep mine in foam lined cases (pluck foam). The foam seems to retain some heat and re-capping, replacing the eyepiece and closing the lid of the box between eyepiece changes seems to do the trick.

 

 

[JOC]

Hi John, forums are wonderful places - I'd been doing the exact opposite taking all the eyepieces out of their containers in the hope that they would get as cold as the surrounding temperatures and not steam up!!  It's a good job I posted as now at least I know.  Many thanks

[rockystar]

On 1/15/2017 at 21:33, Waldemar said:

Yep, when diving into this hobby, or should I say addiction, there will be no time nor money for alcohol and wild women...  
and we did not even talk about imaging... just bottomless... 

"I spent half my money on women and alcohol, the rest I just frittered away!"

On a more serious note, last night was pretty cold and frosty, I only took 2 eyepieces out; I found that I was swapping them about every 10-15 minutes and the other stayed in my pocket. In nearly two hours, I didn't suffer from any dew or fogging, so it must have helped.

My next project is to build a power tank with a variable dimmer switch to control the Dew Strap that I got for Christmas - I asked for the strap, but forgot about the power requirements, doh!

[rockystar]

On 1/15/2017 at 21:33, Waldemar said:

Yep, when diving into this hobby, or should I say addiction, there will be no time nor money for alcohol and wild women...  
and we did not even talk about imaging... just bottomless... 

"I spent half my money on women and alcohol, the rest I just frittered away!"

On a more serious note, last night was pretty cold and frosty, I only took 2 eyepieces out; I found that I was swapping them about every 10-15 minutes and the other stayed in my pocket. In nearly two hours, I didn't suffer from any dew or fogging, so it must have helped.

My next project is to build a power tank with a variable dimmer switch to control the Dew Strap that I got for Christmas - I asked for the strap, but forgot about the power requirements, doh!