Dew Solving Solution- Crazy Idea?

[multiweb (Marc)]

Originally Posted by Jen

Marc they sound like a great idea if someone actually knew what they were doing to make these haha how much would you charge us lovely IIS ladies to make some of these

Originally Posted by Suzy

I'm with Jen, if you are willing to help us IIS ladies out by selling them to us- we would be incredibly grateful astro chicks .

Certainly not qualified to sell this stuff. I wouldn't want your scopes to go up in flames with burning rubber and sticky tapes in the middle of the night. but I can PM you or email more info. I'll make you a deal though. If I happen to meet with you guys at a star party of other we'll have a standard homebrew.

[yusufcam (Colin)]

Originally Posted by Liz

Come up to TvilleSuzy, and I will show you what real DEW is!!

first experience of astronomy was with a reflector up on high range (where the army trains) outside townsville in my youth...

soooo many stars...

so real dew up there would be about 150ml a night?

[pgc hunter]

Originally Posted by Suzy

Hmmm... I really like this solution Sab.
Did you make it yourself, if so what and where did you get the material from? Or did you buy it?

Didn't make it myself, bought the scope second hand from Dave47tuc so I think he made the shield. It appears to be a sheet of plastic similar to the front covers of those plastic pocket display books. Send Dave a PM he'll probably be able to tell you exactly what he used and where he got it from.

[mikerr (Michael)]

Suzy, going back to your original post, which part dewed up first?
I mean was it the main mirror or the secondary?
I'm just trying to get a feel for the best way to attack this.

Michael

[Suzy]

Hi Mike,
It's the secondary mirror I'm having trouble with.

[mikerr (Michael)]

Suzy, I think you are going to need to heat the secondary mirror and cell directly. This has been discussed and carried out in these threads..

http://www.iceinspace.com.au/forum/s...ad.php?t=31846

http://www.iceinspace.com.au/forum/s...ad.php?t=33207

This obviously requires a bit of work that you may or may not feel confident to do. Maybe your telescope dealer would be worth a call.

I have a sct and have just ordered a Dew-Not strap to keep the Corrector Plate warm.
Maybe one of the smaller straps could be wrapped around your Secondary holder. This would of course increase the size of the Secondary obstruction but may not really be an issue.

http://www.dew-not.com/specifications.htm

A controller would be required for the strap and that could be purchased (expensive) or kit built cheap.

What are all the other Dob and Newt owners out there doing for this problem??

I hope this helps or at least gets you some more useful responses.

Michael

[Jen]

Originally Posted by Suzy

Hi Mike,
It's the secondary mirror I'm having trouble with.

Me too

And Suzy yes i hear ya with the soft fluffy clothes i hate the sound of the wosh woosh noise those suits make

[GTB_an_Owl (Geoff)]

well i tell you what Jen

i wouldn't swap the whoosh whoosh noise, the soft warm lining, the minimal inner dress code, the warm and fuzzy all night feeling for the multi layer, knee knocking, teeth chattering alternative for the world

geoff

[jjjnettie (Jeanette)]

I can put up with the wfft wfft wfft of my ski pants.
They're water proof, wind proof and soft and feel like I'm wearing a doona.
I can get down on the ground at the scope and not come up saturated from the dewy ground.

[Jen]

Originally Posted by GTB_an_Owl

well i tell you what Jen

i wouldn't swap the whoosh whoosh noise, the soft warm lining, the minimal inner dress code, the warm and fuzzy all night feeling for the multi layer, knee knocking, teeth chattering alternative for the world

geoff

lol Geoff well can you make some that are also girley like and fluffy and cuddly on the outside too i have an image to withold LOL

[Suzy]

Originally Posted by Jen

lol Geoff well can you make some that are also girley like and fluffy and cuddly on the outside too i have an image to withold LOL

Yes yes what Jen said... and in pastel pink with a cutesy flower motif would be great too!
Thanks Jen, am glad I'm not the only one.

Nettie, I have "Elmo" thick fleecy track pants that keep me toasty warm. I never observe without Elmo.

Well so far it looks like I'm (hubby actually) going to have a go at making a dew shield as Sab suggested. Seems an easy, inexpensive fix, and it seems there good to last for about 3-4 hours. Off to Bunnings in the next couple of days to get some "Cor Flute" plastic and we'll use double sided adhesive velcro to join it. I'm told a two foot long shield is a good size and will make the cap cone shaped (as per Sab's pic). Will also do a little shield for my finders with the same materials/method. Hubby is going to be working on my scope as a Mother's Day present.

Thanks Sab, and thanks everyone for all your help and input so far. If you'll have any other suggestions, please do mention them as it will help others too.
Thank you also Mike for all that trouble you went to with all that information.

Jen, hubby said he will make one for you too (if you're interested) but he wants to see how effective this will be on my scope first.
Big Johnnie will look even bigger and meaner Jen!

[Jen]

lol Suzy yes Johnny will look much meaner with one of those sticking out of it ok let me know how it goes

[RobF (Rob)]

Before you get too carried away Suzy, I would suggest following through on what Sab suggested. I've found this very effective on my 8". I bought a roll of caming foam (1cm foam "mattress") for about $10-$20 from K-Mart camping section, cut into a strip, put velco along the join, and slip it over the end of the OTA. The nuts that hold my secondary vanes nicely stop it sliding down any further. I also bought a can of black spray paint once I was convinced it worked a sprayed the inside black. Cut the strip so the shape is a slightly flared cone (end aperture a bit bigger than where it slips over the scope).

The only problem I've ever had was leaving it lying around after a dark sky visit and my 3 yr almost destroying it playing with the velcro....

Secondaries are particularly vulnerable in Newts. I've been meaning to make a blanket for my main mirror like this too, but usually by the time primaries are dewing up everyone on the field has problems unless they're very well set up with dew heaters. Stubby holder with velcro over the finder works wonders too.

Some pics here if helps: https://picasaweb.google.com/UserRob...83753965595570

[KenNo2658 (Ken)]

Suzy, I did a search on dew shields here a little while ago, and the camp mat (Black of course!) and velcro one works a treat! But the extension above the aperture shouldn't be any more than 1.5 times the aperture. This keeps it from cutting into your field of view. Seems pretty right with the one I made and it certainly helps with the dew!

Ken

[Liz]

I might try to make one again too. I did try the camping mat idea, but dont use it as kept flying off. Hadnt been bothered using the velcro.I also like the look of Sabs more professional job.

There are a variety of materials at Bunnings to use, so might have a look today, but need the velcro to finish it off this time.

Re warm clothes - luckily dont have to worry too much up here, although mid year temps can get down to 13 thereabouts.

[AstralTraveller (David)]

The plus of the dew cap is that it will also reduce stray light hitting the ep and so give you a darker background. The average newt (including mine) need a lot of work to get a reasonably dark background.

[Suzy]

Liz,

Here are some specs on how to do it, which I came across on the link that Mike mentioned earlier.
http://www.astro-tom.com/tips_and_advice/dewing.htm

You can easily make your own. A piece of tough 5/8-inch foam rubber, the kind sold in sporting-goods stores to go under sleeping bags, makes a dew shield that's cheap, durable, and very lightweight. The foam is an excellent insulator, for maximum effectiveness. If you're concerned that the cap might vignette the image (block some starlight near the edges of the field of view), you can cut the foam so it flares open at a very slight angle. A 3° opening angle should allow a 3° unvignetted field of view.
As a rule of thumb, a dewcap should be at least 1½ times as long as the aperture is wide. A side benefit is that the cap also cuts down on stray light getting into the telescope.
Eyepieces too are prone to dewing. Warm radiation from your face slows the process, but humidity from your eyeball and breath speeds it up. A tall rubber eyecup, the kind that extends above the eye lens all around, not only blocks stray light while you're observing but acts as a miniature dewcap when you're looking away.
The same principle works on large scales. Early on a clear morning, have you noticed grass in the middle of a field white with frost or dew while grass near a tree has none? The tree is a giant dewcap, and it can work for you too. If you'll be looking at only one part of the sky, it's nice to have trees around and behind you. Not just your telescope but your charts and accessories will stay dry longer.
Trees also reduce wind problems, but a slight breeze is a good thing. Radiational cooling is slow and inefficient compared to heat transfer with the surrounding air, so even the mildest breeze will keep your telescope nearly up to air temperature.

It's interesting to note that in his article he talks about eyepieces which have the long eye caps being beneficial to keeping dew away on the eyepiece. I've come know this for quite some time. It really does work (my ep's have the 20mm eye relief and therefore longer cups). However, the Denkenmeir ep I just bought (which I love!) has the 20mm eye relief and no eye cup- it dews up!

Hubby wants to try the Cor Flute as it's very light, even tho it may be very difficult to bend (he has an idea for a technique to bend it to shape & is keen to give it a go). Other than that, I got a large black plastic document holder (really large size for drawings/architects) from Office Works for around $20. It's the same black plastic used on A4 display books. So If the Cor Flute doesn't work out, will use that probably unless Bunnings have other alternatives. Will let you'll know how I go.

Thanks Rob for your help and those pics. I like what you have done to those finders .

[RobF (Rob)]

Originally Posted by Suzy

Thanks Rob for your help and those pics. I like what you have done to those finders .

I always had a feeling the stubby cooler from my dive club would come in handy for something else one day....

[acropolite (Phil)]

Suzy, re the cold, a good fitting freezer suit will keep you warm, it's particularly important to keep your head warm, (never mind the hair) your body will shut down circulation to your extremities to keep your head warm, so warm head = warm hands and feet. When we used to wave-sail in the Tassie ( often in temps less than 10 degrees) winter, a neoprene helmet made the difference between numb cold and very blue hands and feet and toasty warm hands and feet.

[Liz]

Hmmm .. saw these on a shopping site - heated animal pet beds/pads??

http://www.dealsdirect.com.au/search...-search-_-6587

The heated kitty sleeping bag might fit over the scope quite well.