Questions about dew and Mak maintenance

[robkmaeda]

Hello,

I just tried to go outside and have look around Lyra after reading about the Ring nebula. I placed my telescope outside about an hour and a half earlier to get it to temperature. It has been foggy and overcast the last few nights, but tonight I can see the stars. When I went out to have a look, I noticed that the scope had a little dew on the outside. The lens caps were on, so the lenses were dry. As I have a dew shield, and being a beginner, I thought I'd see if I could find anything. Unfortunately, my finder scope soon fogged up so that I could only see Vega. Looking through the main scope was much clearer, but I started to see halos around Vega after a few minutes. That's when I called it a night.

My questions are the following:

Should I not have tried to go out tonight with the recent humidity?

Should I have let the scope equilibrate longer?

How can I better fight dew build- up?

What should I do in terms of drying and cleaning the scope and when should I reafix the lens caps?

Thanks a lot,

Rob

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[faulksy]

answers to your questions:

first of all you realy need a due heater and winter isnt even hear yet!

you get the condensation due to warm tube/collector meeting cold air condensating. to get through the night use your missis/yours lol hair dryer on a lw setting dont get to close to your scope though and just blow it over the glass and your finder to will work fine. keep it with you all night. hope this helps

[robkmaeda]

Thanks a lot. So a hair drier is a standard piece of equipment? It seems like the noise would break up the nice peaceful feeling I get when I'm outside at night. Oh well, if it has to be done. I hope my neighbors don't mind.

Thanks again,

Rob

[John]

With maks and SCT's dew prevention gear such as a dew shield or a heated dew tape is practically mandatory. The hair dryer trick is OK but your session has already been interrupted by then. Much better to ensure you don't get dewed up to start with.

Let the dew evoporate off the optics either with the hair drier or when you bring the scope insice - don't wipe it. Keep it capped when you have bought it in and it will clear itself.

But do think about getting or making a dew sheild at least.

[robkmaeda]

Oh, forgot to ask. What kind of dew heater should I get? I looked up some on the internet. It seems I need to get one for the main lens, one for the eyepiece and one for the finderscope. Plus, I would need to buy a powersource. Is this correct?

Thanks,

Rob

[brantuk]

A standard dew tape around the meniscus will do - you can get tapes that plug straight into the field pack - or use a dew controller. You will need a power source to run it - either a mains to 12v psu, or a 12v field battery. Is your scope powered or manual Rob?

[Space Bat]

You can make your own dew heater by using some resisters in some sort of sleeving.....which can all be sourced from maplins..

Stick to low Ohm values as you do want them to get warm

If you really want a challenge you can even knock up a little control box with a pot - to control the output...

You can knock together a dew heater for under a fiver

[JamesM]

I would certainly recommend a dew strip around the scope and if you are actively using your finder to locate objects one for that too. In particular I would recommend the U.S made Dew-Not brand detailed here and can only be purchased from Modern Astronomy as the its sole U.K supplier. They are unique as they use a gel rather than a sewn in heating element which provides a more even heat AND pulls less juice from your power source which could mean longer viewing. I would prefer to use a dew heater controller as well to help regulate the output, especially if you are observing for long periods or when the weather gets really cold and you are interested in conserving energy from your power source. I have seen one or two controllers (two outputs) for around £45. For the eyepiece, I would just rely on the eyepiece cap and as for any other eyepieces you use, I would keep them separate in my pockets to help keep them warm. What ever is left outside will be totally soaked by the end of a session, so maps and books etc are best left under a plastic sheet to keep them dry. I personally wouldn't bother with a hairdryer as they pull too much juice from your power source and are too noisy. Prevention is better than cure and as a cure, the hairdryer is only a temporary measure.

James

[robkmaeda]

Thanks for all of the help.

My scope is powered (alt/az tracker). I still haven't purchased a 12v rechargable battery, mostly because my local telescope shop didn't have one in stock when I bought my telescope. I guess I should order one. For now, I am just running a long extension cord from the house.

I'll check out the gel dew strip. Although I live in France, right by the Swiss border, I'm actually American and I'm actually going to visit my parents next week. I might be able to have one shipped to them before I go.

Thanks again for all your help.

Rob

[M4lcs67]

As an addition to this post, although I haven't had the need to do anything with my scope so far (I have a dew sheild that I haven't used yet), but as my scope is motorised I have a Maplin 3 in 1 powertank. If I decide that I need a dew heater are there any 12v splitters out that use a car cigarette lighter socket, so I can potentially power the scope and dew heater together through my powertank?????

[x6gas]

You can buy a 5 way splitter from Maplin.

Just beware that the connectors are daisychained (I think) and be mindful of the maximum power rating. You don't want your mount to be struggling for amps because of a wire that's not up to the job...

[hemihaggis]

i live in cold , wet , damp, cold wet , humid , rainy , damp , drizzely , frezzing , boggy , soaking wet , swampy , even colder , even wetter , raining for months , the sun has disappered , its like living inside a cloud scotland , and i have never used a dew heater , i have a home made sheild ,and thats all , and i have never had a problem with dew , i think its just another set of wires to dangle off scope and more power to use your batterys ,

so if i dont need a dew heater in scotland ...do you need one in france ??

[robkmaeda]

All I can say is that my scope was completely fogged up after a short time without lens caps. The exterior was also pretty wet. I have a dew shield and it seemed to help protect zhe main lens. As I understand it, dew forms on the basis of the objects being brought to temps below the dew point. This should only happen when the temperature drops faster than the humidity can compensate for. Perhaps in Scotland, the temperatures change more slowly? I don't know, I'm new to all this and have never much thought of dew formation before.

Rob

[Brinders]

i live in cold , wet , damp, cold wet , humid , rainy , damp , drizzely , frezzing , boggy , soaking wet , swampy , even colder , even wetter , raining for months , the sun has disappered , its like living inside a cloud scotland , and i have never used a dew heater , i have a home made sheild ,and thats all , and i have never had a problem with dew , i think its just another set of wires to dangle off scope and more power to use your batterys ,

so if i dont need a dew heater in scotland ...do you need one in france ??

I can only think your are very lucky not to experience any dew. The guy is getting dew on his scope and it is something I and many others on here with Maks and SCTs are only too familiar with. As has been said, prevention is better than a cure and a dew heater with a regulated output to provide just enough heat to keep dew at bay is the way to go. On some nights a dew shield may well be enough, but as the still cold nights of winter approach, I know I'll be glad of my dew heater; it will make the difference between being able to observe and not.

Brinders