How to take a scope outside (to minimise dew)

[SimM]

I don't know the first thing about "dew" control. Is there any FAQ on how to manage dew especially when moving from a relatively immune newtonian?

If I keep my newtonian scope in the house (heated and dry environment), what's the best way to take it outside e.g. in the winter months?

Should I leave the eyepiece adaptor covered? Leave the scope cap on? Carry it outside and set it up pointing slightly down, leaving it to cool down e.g. 30 - 50 minutes?

When bringing it inside, Leave the eyepiece out and the cap off. Carry it inside and leave it to warm up. Later, cover the eyepiece and replace the scope cap?

I don't have either a refractor or SCT but plan to eventually buy these. Will I do the same as above (but add a dew shield cover when setting up an SCT outside)?

Where is the optimum place to store a scope e.g. a shed, unheated garage, in the house e.g. an unused (unheated/low heat) bedroom?

NB It's been awhile (about 25 years) since I used it (showing my age and (lack) of enthusiasm, until now...

Simon

[RT65CB-SWL]

Hi @SimM / Simon and welcome to SGL. 

Looks to me you have answered your questions. 

15 minutes ago, SimM said:

Should I leave the eyepiece adaptor covered? Leave the scope cap on? Carry it outside and set it up pointing slightly down, leaving it to cool down e.g. 30 - 50 minutes?

I tend to leave everything uncovered/off.

When I bring my 'scopes indoor from the outside, I remove all caps and let everything dry naturally. I sleep... and check all is OK before replacing when I am awake again. 

Edited January 10, 2020 by Philip R

[NGC 1502]

Newtonian -
Storage - if possible should be - cool, dry, dust free, close to where it’s used, of course secure......

Taking it out - for fastest cooling, caps and covers off, tube angled up, if you have a primary fan turn on.....

Bringing it in - all caps and covers on, storage as above, after several hours / next morning, remove caps and covers allow plenty of time to dry out then replace caps and covers when all signs of damp are gone.

If you bring a cold scope into a warm building with the caps and covers off, the optical surfaces will dew up fast and take much longer to dry out.

That’s what works for me.....

Ed.

[Carbon Brush]

Excellent advice from Ed.

Just to emphasise. Covers on before you come inside.

The amount of moisture that air can hold depends on temperature. It is not a simple relationship.
It is that cold air can hold a lot less water than warm air.

If you have a big scope tube full of cold air, it contains little moisture.
So when capped (sealed) to bring inside there will not be condensation as it warms.
As the caps are not perfect seals, it will eventually exchange air with the house but will be warm before this happens.

A house is warm, and importantly quite humid by comparison with the outside.
Think of you, the dog, the cat all exhaling moist air.
Then of course showers, hair dryers, steaming sinks, cooking, etc all add to the moisture.

So an uncapped cold scope chills the warm moist air that enters the tube and you get condensation.

If the scope does dew up when indoors, just give it a blast with a hair dryer to bring up the temperature.
It is reasonable to expect the tube to dew on the outside, but not inside surfaces.
Obviously you aren't bothered about warm air currents or uneven heating.

HTH, David.

[Louis D]

In the winter, I cap everything and close my sealed Pelican-style eyepiece case(s) before bringing everything inside.  The dewpoint outside is super low in the winter compared to the dewpoint inside the house, so I seal that dry air in with the optics as they warm up.  In 20+ years, I've had zero mold issues.

In the summer, I bring everything in caps-off and cases-open since the dewpoint outside is generally much higher than inside my air conditioned house.  I then leave them out to dry until morning when I cap and close everything and put them all away.

In the shoulder seasons, it really depends on the dewpoint.  Anytime there is noticeable dampness, I err on the side of allowing things to dry out inside rather than trapping that moisture with the optics.

This applies to Texas which swings from swamp-like summers to desert-like winters.  I haven't dealt with dry summers and wet winters or non-air-conditioned houses.

[ronl]

You could always get one of these, https://www.firstlightoptics.com/dew-prevention/astro-essentials-dual-fit-desiccant-cap-red.html

not that cheap, but it works really well, cheaper than new optics.

[joe aguiar]

Dew is mainly an issue in summer months when it's hot. Unless u live in the tripocs where theres no winter but has rainy season, then u may have to deal with dew yr round.

I norm just take it out let it cool then obseve. Larger scopes need more smaller less time. Unless it's a sealed units.

Since yours is small 20 min is probably fine but depends where u live.

If u mean condensate when u bring it in then that's bit different.  I just cap everything b4 bringing it back in and it drys. I have never had any issues.

Joejaguar 

 

Edited January 10, 2020 by joe aguiar

[SimM]

I have read all the tips - thanks.

It seems to be take it outside and then take the cap off, take the cap off before taking it out. Always put the cap on before bringing it inside and when it's done, leave the cap off to circulate the air before putting it away. Best is to keep it close to the outside temperature e.g. from the house to the garage to the back yard. Also learned hat some of these rules don't always apply e.g. different seasons and the house temperature vs outside.

[Nicola Hannah Butterfield]

On 10/01/2020 at 07:56, NGC 1502 said:

Bringing it in - all caps and covers on,

 

This is what I learned about camera kit, so it is the same principal, place camera and lens in a plastic carry bag whilst outside, once the camera/lens is room temp remove bag should avoid any moisture. i appreciate telescopes are bigger (usually) but what I do is cover optics, focuser cap, I have elasticated camera bag cover which is ideal for the bottom of my newtonian and aperture cover on the front, the tube will be fine and just needs a wipe down once any moister has evaporated.

[Sunshine]

when i bring my scope in from cold winter weather i leave it as is, caps off, it dews up the minute i get in, ill just leave it for a bit caps off and the dew evaporates.