A couple of newbie questions about moisture :-)

[Beagleboy]

I managed to view my first, absolutely 100% certain deep space object on Friday night, The Ring Nebula. However whilst oogling at this tiny grey smoke ring in the sky, I became aware of a couple of issues so thought I'd ask here for advice.

 

I put the scope out in the back garden around 8pm (just before the rugby kicked off), and didn't sit down to start viewing until around 10.30pm, thinking this would give the scope (Skywatcher 200p), plenty of time to equilibriate. During this cool down period, I left all the covers in place. Should they be on or off?

 

Whilst viewing, I quickly became aware of dew forming on the lenses. Is it okay to use lens wipes to clear this away?

 

Finally, when storing the scope away for the night after a viewing session, I replaced all the covers before bringing it inside, but afterwards, once the scope has warmed up again, should I remove the covers to let the air exchange, or does most of the moisture condense on the outside of the scope?

 

Cheers for any help!

 

C.

[michael.h.f.wilkinson]

I tend to leave covers on when I put the scope outside to reach thermal equilibrium to prevent dew forming on the optics. When I take it back in I leave it uncovered (horizontally, with dew shield on, to prevent dust settling on the optics) until all the condensation has evaporated. Only then do I put it away in a flight case (with a load of silica-gel packets)

[rockystar]

Here is an article I read just last week when I was also researching it after I had exactly same issue with my eyepieces: http://www.skyandtelescope.com/astronomy-resources/dealing-with-dew/

It had some reasonably good advice and info, I'm sure some of the more experienced guys here will offer their own good advice too :-)

[laudropb]

Hi. Never wipe your lenses when they are wet. Any dust there is liable to cause scratches on the lens and you may also damage the lens coatings. The lens must be allowed to air dry. If you see dust on an eyepieces blow it of with an air brush. Never try to wipe it off.

I use a dew shield on my 200p and seldom have problems with my mirror. I keep the finder scope capped when not in use. Eyepieces are more of a problem. When not in use I keep them warm in my pocket. If they mist up I just use another eyepiece. I have used a portable hair dryer to warm them, but find that this only gives temporary relief.

[Beagleboy]

Aaah, never thought about capping the finderscope when not in use. It was definitely the finderscope that I was struggling with more so than the eyepieces, although I'll try Laudro's wee trick with the eyepieces as well. It's probably our Scottish air that's causing all the problems anyway! Thanks for all the help folks!

Craig xx

[Thales]

This is a key question I've discovered - for some reason 2 nights ago, my entire mount and tripod was dripping, though the scope was ok.  The whole set up had been in the garden since noon for sun obs, and I left it there until after midnight to try to locate Neptune.  I noticed when I went out in the evening that the tripod legs were sopping, but the scope itself seemed dry.  When packing up I've been capping the dewshield in the garden then taing the scope down and leaving it in doors for a while(cap on) to 'warm up'? and then I pack it away.  Should I be taking the cap off for a while again before packing? 

cheersJeff

[Farrow]

Coincidentally, I managed my first DSO on Monday of this week, and it was also the ring nebula. Nice easy target to find... well, the second time I tried anyway 

I found that by the end of my observing I was having some dew problems, so I'll be constructing a dew shield for my newtonian, but I have my own related question to the OP:

Everyone always says that you should put the 'scope out 30 minutes or so before observing for the air in the tube to equalise with the air outside. However, unless I'm misunderstanding the way they work, the entire point of dew shields seems to be to keep warmer air near the mirrors/lenses so they don't form condensation... Aren't the two rather incongruous?

[Charic]

On my Dob, I allow the scope to cool / warm with the OTA at about 45° tilt, and with the OTA dust cap in place and the 2" aperture cap removed. The chances of anything entering a 2" aperture is remote, but sufficient enough to allow the air to move through the scope.

To speed the process, I have a flexible hose that sits over my focuser, the fan and 9v battery at the other end can be placed wherever I please, except on the floor, incase anything small wants to climb inside the flexi-pipe, but Im sure the fan will mince anything that tries?

If you view through your scope ( Newtonian ) at high powers, having taking your scope from a warmer environment to a cooler one, you can observe a kaleidoscope of grey swirlling vortices, this is the effect of tube currents and the thermal boundary layer over the face of the mirror. Watching this, its evident to me that the cooling process is indeed quicker if fan cooled, but I prefer to leave the scope to cool naturally.

[bob9039]

Learn something new everyday, I'll stop wiping my eyepieces with lint free cloth / Q-tip, ouch my poor EP's.

Will have to invest in lens cleaning equipment.

[Dave In Vermont]

May I suggest something for cleaning eyepieces - when they need more than a good blow of air - after a night out? It's called a Lenspen. These are made in Canada and are widely available - with many different company names on them. Here's they on Amazon:

http://www.amazon.com/s/?ie=UTF8&keywords=lenspen+lens&tag=googhydr-20&index=electronics&hvadid=7251446048&hvpos=1t1&hvexid=&hvnetw=g&hvrand=13037885705541538908&hvpone=&hvptwo=&hvqmt=b&hvdev=c&ref=pd_sl_3gj5eozwqb_b

I always carry one. Not for use on mirrors or corrector-lens on an SCT.

Enjoy!

Dave

[swamp thing]

Everyone always says that you should put the 'scope out 30 minutes or so before observing for the air in the tube to equalise with the air outside.

I don't

I start observing immediately after set up. IMO you're wasting observing time by waiting around for the scope to cool. Plus, as you've noticed cooled down can equal dewed up.