Shed Storage

[Stardaze]

How do those that leave their reflector in a shed or observatory overnight (after using) stop dew over night? I packed away last night with the first frost of the year forming but having just looked at my scope it’s dewed up inside. The pics show the mirror which I had this happen last week too. I’ll let it dry out today with the help of a heater in there but I assumed that the shed cover alone would stop the dew?

Edited November 5, 2021 by Stardaze

[Carbon Brush]

The amount of water vapour that air can hold reduces with reducing temperature.

Dew (condensation) on any object is the result of either the air around becoming saturated, or the object being colder than the air.

In the case of a scope mirror put into an unheated place, it has been pointing at a clear sky for a long time and is below ambient temperature.
I know this is counter intuitive, but believe me for now.

If you take your cold mirror into your warm and humid house, it chills the air immediately around, so you get condensation.

The only sure way to keep condensation at bay is to heat your mirror after use.

Whether in my observatory, or bringing kit into the house, a few minutes with the hair dryer gets things sorted.

HTH, David.

[Tiny Clanger]

11 minutes ago, Carbon Brush said:

The amount of water vapour that air can hold reduces with reducing temperature.

Dew (condensation) on any object is the result of either the air around becoming saturated, or the object being colder than the air.

In the case of a scope mirror put into an unheated place, it has been pointing at a clear sky for a long time and is below ambient temperature.
I know this is counter intuitive, but believe me for now.

If you take your cold mirror into your warm and humid house, it chills the air immediately around, so you get condensation.

The only sure way to keep condensation at bay is to heat your mirror after use.

Whether in my observatory, or bringing kit into the house, a few minutes with the hair dryer gets things sorted.

HTH, David.

Simple physics isn't it ?

I find it fascinating the way that some things like this fall outside general 'common sense' and loved working out how to explain it to the small folk I used to teach.

Heather

[Stardaze]

Thanks all, I understand the physics but how do those, who store outside, negate the issue, pre heated observatory/shed? I’ve lost half of my garage through building a utility and so was hoping to utilise the shed to store my dob for the most part. The scope had a slither of ice on the back when I wheeled her in last night. Was thinking of a bigger and better equipped shed next year too. 
 

@Carbon Brushdo you use a hairdryer before you leave for the evening? I need to get a little portable one.

Edited November 5, 2021 by Stardaze

[Carbon Brush]

@Carbon Brushdo you use a hairdryer before you leave for the evening? I need to get a little portable one.

As my earlier post...
Whether in my observatory, or bringing kit into the house, a few minutes with the hair dryer gets things sorted.

David.

[Nik271]

I bring my scopes into the house overnight after observing  precisely for this reason but I have Maks which are very compact. One option is to put your Dob back in the shed with the front cap open(just cover with a towel to stop dust). Once dry put the cap back on the next day.

[Stardaze]

19 minutes ago, Nik271 said:

I bring my scopes into the house overnight after observing  precisely for this reason but I have Maks which are very compact. One option is to put your Dob back in the shed with the front cap open(just cover with a towel to stop dust). Once dry put the cap back on the next day.

I’ve rolled it back into the garage and left the cover off today, which has dried it out. Trying to keep it out of the garage really so I need to rethink the strategy. I might give the mirror a clean though as I’m sure it’s not great having it dew’d up. 

Edited November 5, 2021 by Stardaze

[Carbon Brush]

Beware mirror cleaning. It is very easy to do more harm than good.
There are lots of posts about this on SGL, covering assessment and cleaning.
Bottom line. Unless it is really really mucky, or has something nasty/corrosive on there, leave it alone.

HTH, David.

[Stardaze]

1 hour ago, Carbon Brush said:

Beware mirror cleaning. It is very easy to do more harm than good.
There are lots of posts about this on SGL, covering assessment and cleaning.
Bottom line. Unless it is really really mucky, or has something nasty/corrosive on there, leave it alone.

HTH, David.

Thanks David, there's definitely two camps regarding mirror cleaning. I had to do the secondary due to me touching it early on by accident, so I'm certainly not worried about doing it. Was planning to do it tomorrow most probably. 

[Louis D]

Just don't try to use canned air to blow off dust as this is the result:

 

[Stardaze]

3 hours ago, Louis D said:

Just don't try to use canned air to blow off dust as this is the result:

 

Ouch!

I ended up cleaning the mirror in the end. It wasn’t too bad really but there was a bit of dust more concentrated on one side and a few larger chunks of something - looks perfect again now 😀

The only snag I found was actually getting the whole mirror assembly back onto the tube. Bresser have added some sticky felt pads between the screw and insert where the tube slides into, two of which were compressed down. I’ve removed those two in the end, as once damaged they wouldn’t repair very well. Im sure others have found this too? Maybe @johninderbymight have? Only seems a little padding for the tube to sit against.

[johninderby]

As I remember the tube simply slid into place on my 10” Bresser and don’t rember any sticky pads.

 

Edited November 8, 2021 by johninderby

[Stardaze]

2 minutes ago, johninderby said:

As I remember the tube simply slid into place on my 10” Bresser and don’t rember any sticky pads.

I should have taken a picture but you may not have noticed them as they were folded down over the 4 inserts. I think next time I’ll lay the OTA out a little better for removal, I ended up clamping it up on the base with a strap, so I may have squashed the pads the first time of trying to get back on.

Did you sell your dob in the end John? This one is definitely my ‘learner scope’! 

[johninderby]

Yes I did sell the 10” dob. Found I was using the CC8” a lot more.

[Stardaze]

1 hour ago, johninderby said:

Yes I did sell the 10” dob. Found I was using the CC8” a lot more.

In the pic above, looks like you didn’t have any. 
 

Im torn with the next scope, next year. Was just going to go for a 102 R model but then I do fancy the CC8”. The frac is a bit more flexible though. 

[johninderby]

17 minutes ago, Stardaze said:

In the pic above, looks like you didn’t have any. 
 

Im torn with the next scope, next year. Was just going to go for a 102 R model but then I do fancy the CC8”. The frac is a bit more flexible though. 

You know where this is going. 😁 The 102 and CC8 would compliment each other nicely. 🙂

[Stardaze]

2 hours ago, johninderby said:

You know where this is going. 😁 The 102 and CC8 would compliment each other nicely. 🙂

The pic of yours together does look rather nice. One at a time I think..