Bringing in scope after observing

[cyborg421]

My 10" Dob arrived today. 2 dents in side... anyway FLO said I can use it until I get a replacement. Had about an hour on Jupiter tonight. Dark band very clear . Awesome!

Question do I need to leave the scope open until it has warmed up again to stop water condensing on the mirror after I bring it in from outside. I assume so.

Simon

[mdstuart]

I think whatever you do dew will form if the mirror is cold. Ultimatly try to bring the scope in to an out house rather than a warm house?

It does not seem to have caused a big issue though for me over a few years, those mirrors seem resiliant to a bit of dew from time to time.

Mark

Mark

[cyborg421]

Cheers Mark,

I still undecided whether to store the scope inside or in a bike shed that I have. The bike shed would minimize the dew problem. What do other people do?

Simon

[John]

I bring mine into the house with the caps on, and leave them that way. Dew sometimes forms but it soon dissapears, with no adverse effects.

[Chris H]

If the bike shed is unheated then it would be a good option, not only would you not get condensation forming after you put it away but it would also dramatically shorten your cool down times, making the 10" Dob a grab and go scope. One thing to be wary of is if the shed is a little damp then you can get condensation forming on the mirror early in the morning.

My scope lives in my shed in the garden with a dehumidifier to keep it company.

[Moonshane]

lots of people will have differing views on this.

my scopes are cosseted and live in the house; I don't mind planning ahead and putting them out earlier although it's a pain in the winter or rapidly changing (usually deteriorating!) conditions. when I bring them inside I leave the caps off the scopes and the eyepieces and the mirrors always dew up but as long as you let it dry off and don't tough anything it clears away clean in the morning.

I then cap everything up and pack it away so I don't get the rolling pin slapped in the hand treatment.

personally I fear mildew / fungus more than dew / dust so always let them dry off in the sir before I pack up. if I am in the field I cap up but then uncap when I get home and do the same. always leave your tubes at an angle so dew cannot drip directly on the primary and leave EPs on their sides to reduce dust.

[matteboy]

Brought my scope in about nine and just checked it and dew has formed on the main mirror, lots of spots on it, going to check in the morning and hope it goes back to how it was before I took it out, proper panic attack until I read this!

[perrin6]

I bring the dob in and de-dew the mirrors with a hairdryer then check 20 mins later & redry if necessary. I do this because any acid pollutants on the optical surfaces might dissolve in the water & become active. Lots of chemicals dont react unless in solution. I thnk I read somewhere mirror coatings last longer if dry.

Does this make any sense ???

[matteboy]

Brought my scope in about nine and just checked it and dew has formed on the main mirror, lots of spots on it, going to check in the morning and hope it goes back to how it was before I took it out, proper panic attack until I read this!

Checked this morning, all OK and back to normal, panic over!

[garethmob]

i always bring it inside the house tilt the telescope down and leave till morning before i recap, let it all dry out, dont want any hairy fungi stairing at me through the lens:P

[bish]

When I have been out all night at Kielder my primary mirror has been totally misted up in the morning so I just left the cap off out in the sun and it cleared no probs. Generally though I always keep the caps on when taking out/ bringing in.

[johninderby]

I use AastroZap breathable caps on my OO 14" dob and put them on as soon as I bring the scope in. Takes care of letting any moisture out of the tube. Unfortunately no one seems to stock them in the UK.

John

[sixela]

To avoid dew formation, you have to seal the scope: that means caps on front and focuser, and something to seal the back (a shower cap is useful, unless for very large scopes). That way, the cold air inside the scope will actually be heated and its relative humidity will decrease.

If you don't seal the scope, the air will be replaced by air from the inside of the house, which will then be cooled to below its dew point by the mirror: instant dew guaranteed.

Leave it sealed for a couple of hours (or until the morning) and then check for dew, because if the sealing was unsuccessful you don't want the dew to stay there for long (and pick up dust before it dries, depositing it on the mirror). If there's dew, either remove it with a hair-dryer or leave the scope unsealed until it goes away, preferably in a relatively dust-free environment.

[F64]

how does that all effect a refractor?