Dew Issues

[Pauly]

I read a lot about people having problems with dew settling on their kit and employing hairdryers, heater strips etc. to help control the problem. In my so far limited experience I have only suffered dew-ing once, and it was limited to the exterior of the scope. Does it ever get worse than this, will it setttle inside the tube and on the optics?

[Sparrow]

I don't know what your scope is but if it''s a schmidt then the dew will settle on the corrector glass at the front. If a refractor then it will settle on the front lense. If a newtonian then yes it will settle on the secondary mirror at the top of the tube - I've never seen it on the main primary mirror of my newt though.

[Astro_Baby]

Its insidious and gets everywhere on a bad night. Newts get it on their secondary mirrors but a deshield will cut it down and even get rid of it under all but the worst conditions. SCTs and Maks get it super bad and almost always need a dew shield and a heater to kill it off, refractors almost always have a deshield as part of their design and seldom seem affected.

Hairdryares are useful all round anti-dew for dealing with Newtonians secondaries, eyepieces and finderscopes.

I have seen it so bad that the primary started to go on my newt and after attempting to use the 180 mak without a dew heater I just gave up - the scope was dewing faster than I could remove it with a hairdryer.

Smaller Maks and SCTs can get away with a dewshield very often.

[Breakintheclouds]

Around this time, last year, when I was starting out, I read so much about how people hated dew, and what they did about it, and I too thought "What's the big deal? It doesn't seem so bad". Well, in a couple of months, you'll see! I know what Astro_Baby means about it getting so bad you just give up - I had a few nights like that last year.

A 12V hair dryer was one of the best things I've bought: 12v hair dryer - Google Product Search

[LukeSkywatcher]

Its insidious and gets everywhere on a bad night. Newts get it on their secondary mirrors but a deshield will cut it down and even get rid of it under all but the worst conditions. SCTs and Maks get it super bad and almost always need a dew shield and a heater to kill it off, refractors almost always have a deshield as part of their design and seldom seem affected.

Hairdryares are useful all round anti-dew for dealing with Newtonians secondaries, eyepieces and finderscopes.

I have seen it so bad that the primary started to go on my newt and after attempting to use the 180 mak without a dew heater I just gave up - the scope was dewing faster than I could remove it with a hairdryer.

Smaller Maks and SCTs can get away with a dewshield very often.

I live on the east coast of Ireland and the dew here can get so bad at times (at any time of year) that it is almost a good investment to have your gear take swimming lessons.

Trust me it is that bad at times.

I have a small 90mm refractor and a 130mm reflector and i have to say that so far i have not had a problem with dew on the 130mm reflector (i have a dew shield/shroud made out of a camping mat on it). The refractor on the other hand has nearly drowned more then once. It has the standard (way too short) dew shield on it that came with it but that does not stop the lens from fogging up and becoming soaked in dew. On a really bad night i find myself having to wipe the lens of the refractor every couple of minutes.

Bins are the same. They fog up/run with dew every couple of mins, so i also made a couple of dew shields for my bins out of the same camping mat as i did for the 130mm scope. The bins have not had a dew issue since.

[Pauly]

Sorry everybody, it's a 6" Newt. My only other concern is, if it gets that bad, will it affect the electronics on the mount?

[Astro_Baby]

Strangely even though I have been out when the dew is so bad that the scope looks like its being held under a running tap the electrical gubbins seems fine. cared me witless the first time out with a GoTo scope by how much water was running off of stuff but the scope never seems to mind.

On the optics though is a real downer - SSP a few years ago was dreadful and people were swearing all night about dew wrecking the view of everyone. I had a deshield so was fine but lots of people had convinced themselves it wasnt lilley to be a problem.

You can make a deshield easy enough but I just bought one cos it seemed less hassle.

[blinky]

I think with a 6" newt you may be OK - the only real problem might be the secondary dewing up but thats easily solved with a high wattage resistor glued to it and a dew controller.

[Sparrow]

I think with a 6" newt you may be OK - the only real problem might be the secondary dewing up but thats easily solved with a high wattage resistor glued to it and a dew controller.

A word of caution - I read in a thread here recently about someone who's secondary plummeted to the bottom of the tube smashing the primary mirror when heat was applied to it as it's held in place with adhesive. I have my homemade dew controller which I actually made for my previous scope (a schmidt) but I've "resisted" applyong a resistor to the seocondary since reading that thread.

[Bigwings]

My SCT used to get the hairdryer treatment . Recently I got a dewband and controler. Strange but we aint had a clear night since.... BEWARE

[Pauly]

Nooooo, the dreaded 'new kit cloud' syndrome

[Astro_Baby]

That secondary that dropped onto the primary may have been me - it was reported on CN some time ago and a nasty mess it made of both mirrors too. I was going to have a dew heater on my secondary but after reading that I thought I'd leave well alone. I think (from memory) the CN accident was someone with a dew heater that went wonky (or more likley a dew controller running amuk).

Besides if you dew heat the secondary you have to run wires to it and that means thicker spider vanes. With my 8" and a decent dew shield I have yet to suffer really major problems from secondary dewing - its happend once or twice at most so I tend to leave it alone.

[Earl]

I was just taking my Flats last night and the stupidly sloppy Dew shield on my Rev 80 slipped without me noticing and the next thing i knew was Dew.. and not the Mountain Dew

Messed up my Flats grrr

I now have some royal mail rubber bands sat on my desk ready to be attached to the scope to hold the stupid thing in place !!!

[Pauly]

I must admit that the idea of glueing a resistor to the secondary didn't appeal to me for several reasons. Firstly the secondary mirror glue thing, secondly the wire thing that AB mentioned, and also I wondered if the rising heat would not be an issue optically. I wasn't unduly worried about using a plain resistor, after all thats all any heating element is.The real issue with the dropped secondary surely must have been an out of control controller. If I start to have problems I think my first step will be a dew shield, and I'll take it from there.

[Skills]

What's the drill for storing your scope and bits after a dew-ridden evening?

I have a dob and tonight it was all pretty misted or wet: eyepieces, finder and OTA. Should I pack away with all dust caps on or is it preferable to let stuff dry before locking in the dew?

[Talitha]

What's the drill for storing your scope and bits after a dew-ridden evening?

I have a dob and tonight it was all pretty misted or wet: eyepieces, finder and OTA. Should I pack away with all dust caps on or is it preferable to let stuff dry before locking in the dew?

The outside of the scope can be dried with a towel, but let the optics dry off before you cap them. I've read nightmare-ish stories about mold/mildew. It's nasty stuff, and best avoided.

[johnh]

I had bad dew problems on secondary with my aluminium tube Newtonian as it lost heat easily so I made a foam nose piece as electrical heater was too complicated with wires and all. The foam nosepiece insulates brilliantly for all night dew free imaging. I got the foam mat from Ebay for a few pounds and superglued it together to form a fluted tube that slides on the Newt. Bringing in scope you need to heat up tube and drive off condensation with hairdryer before sealing as coatings won't last long with water present for prolonged periods.

John.

[Pauly]

I generally leave my stuff unsealed in a warm place till the morning and then put the covers on.

[Uranium235]

If youre going out tonight, expect more of the same.

Whenever you get a day of rain and then clear skies at night its nailed-on that youre going to get dew problems. The other night it was so bad my dslr was literally dripping with dew... n0t g00d.

What was more disturbung though was that the 240v extension was also wet from dew. So if it clears tonight, all power adapters and mains plugs as going into a box to keep the moisture off.