Dew Shield - Shield, Dryer or Heater

[KEJ]

Hi all

Just a brief background first, I am pretty new to Astronomy as in approx 6 weeks and last night I popped out hoping to catch Saturn, so I set all my Kit up outside around 21:30, thinking get out there early to let the kit acclimatise and have a look around at other objects.

I have a Meade 8” SCT LX10 EMC, a Philips webcam and now a Meade DSI II Colour camera, so set the tripod up facing North, plugged the camera in and into the laptop, focused on a star and the motor kept it pretty much dead centre of the screen for 10 mins etc, so I was thinking perfect.

After about 20 minutes I popped around the front and discovered the front lens or aperture was covered in Dew.

My question is what is the best Dew prevention?

1) Dew Shield

2) Dew Heater

3) Hair dryer

Has anyone any experience of all or any and do any work 100%, any I should not use etc?

And finally for a Dew shield any good links or cheapest places to buy?

Also do the rollup versions work as well as the fixed plastic ones?

Finally do they also help to keep light pollution out?

Hopefully thanks

Keith

[davehunt]

Dew shield-rolled corrugated cardboard,sellotape.Adjust according to needs.Acts as good light shield as well,if you have street light problem.That is,unless you want to accumulate expensive gizmos that work no better than the economy versions. My roll came from e bay,£3.65 delivered,with enough for dew shields galore and lots of parcels for those gizmos you will get round to selling eventually.Happy gazing.

[david o]

Hi Keith,

A foam camping mat cut to size and held closed on the 'scope with Velcro strips.

It'll need to extend out beyond the meniscus lens by at least twice the diameter of the aperture.

[KEJ]

Dave's thank you, very good ideas and comments and out of interest have any of you tried the alternatives?

The only thing I am thinking with cardboard to you end up with bits stuck to your lens?

Also how well do these things actually work? ie: take last night say it took 30mins for dew to form(and I know there are other factors) but based on two similar scopes side by side and one with and one without, is it 30mins vs 60mins or no they will do you for a few hours?

Thanks

So for me then worth trying approx 16" of rolled up foam or corrigated

[MorningMajor]

I made mine out of some radiator reflecting material and black duct tape - cost me next to nothing and works a treat!

[Doug]

Hi Keith

I use a Orion Dew shield £28.00 from www.telescopehouse.com

www.virtualvillage.co.uk I use a small car hair dryer 12V of a battery works well about £11.00

Hope this helps

Doug

Essex

[Brinders]

I think it probably depends on the local environment. Where I live in Blackpool, dew is a terrible problem particularly in the winter, spring and autumn, unless (as last night) there is a pretty strong wind. I therefore use both an Astrozap dewshield ( Dew Prevention ) and a heater tape and Dew-Not controller ( tp://www.dew-not.com/dew-not-desc-01.htm ).

I think that a hand held dryer is probably not much use if dew is a real problem: SCT's with their large corrector plate are big dew attractors.

Brinders

[swamp thing]

Hi Keith

Dew can ruin any nights observing any time so I attack it with:

A dew shield, dew heater tapes and a 12v hair dryer.

I drive quite a distance to my observing site and don't want dew being the deciding factor on when its time to pack up.

I think it's best not to rely on one system just in case.

A 12v hair dryer is particularly useful as it can be used on anything with dew on which the others cannot.

Regards Steve

[Mr Spock]

I've never quite worked out why people spend hours waiting for their scope to cool, then heat it with tape or a dryer... ***puzzled look***

A dew shield should work if it's long enough.

[david o]

Keith,

If the dew shield is nice and long it should keep the dew off for a couple of hours at least, just by itself - even in moderate to bad conditions.

Another advantage is that it'll function as a light shield. Keeping out stray, unwanted light and improving the contrast to some degree

[rowan46]

I mainly use a home made a dew shield on my sct which is pretty much essential for this type of scope. but if you can afford it a dew hweater as well would be a good investment. The shield has the added bonus of cuttting out stray light from the sides and thus improving sky contrast but there have been times when even a dew shield hasn't been enough and I wish I had had a dew heater this hasn't happened often but it seems to me a shame that if you can afford a dew heater and don't have one there may be the occasional night that gets wasted. Hair dryers work but they are incredibly noisy in the dead of night

[MorningMajor]

Hair dryers work but they are incredibly noisy in the dead of night

Good point - most people think we're pretty weird walking about the garden in the dark as it is - but with a hairdryer as well?????!!!!

[KEJ]

Gentlemen some really good advice, being a Sunday and hopefully a clear night down here I popped out after various comments and bought a sleeping bag mat and made this to give it a try in a minute.

[KEJ]

minute, I would like to try and get Saturn tonight.

Next job tree cutting I think.

Thanks

[KEJ]

If you think a hair dryer is odd, wait until they see me walking around the garden with this on my head.

[MorningMajor]

Looks good - you might want to cover the inside with something like black duct tape to prevent any odd light refelctions upsetting your viewing

[KEJ]

Sim thanks I will have a think on that - might be differicult now as I have stuck it.

Well just come in from outside after approx 3-4 hrs and a very, very slight haze on one side, certainly seems to have worked on the Dew front.

Thanks

All

[KEJ]

Sim I took your advice and bought a tin of matt black spray paint and gave it a go over on the inside and out, might need another can to finish off but a lot better.

Cheers

[MorningMajor]

Sim I took your advice and bought a tin of matt black spray paint and gave it a go over on the inside and out, might need another can to finish off but a lot better.

Cheers

Excellent - delighted it worked - the only reason I used tape was a worry whether the paint might flake off?

[Slangers]

I invested in the Orion Dewzapper and haven't had a problem since. This week I added a homemade lens shade made from a camping mat and gaffer tape. I've got it to cut down stray light rather than dew.