condensation in observatory

[mattifor]

As I have explained in previous post, I entered this stargarzing adventure following inforced retirement through bad health and pursuasion by my long suffering wife who has been anxiously trying to find a usefull passtime for me.

She has eventually persuaded me to take up this hobby and join her is stargazing.

So I went and purchased all the equipment for her and got quite interested in the process.

Now I have a problem. I hope some one here can advise.

After damaging my wifes 11" Orion optics Newtonion telescope by tripping and landing on top of the OTA whilst taking it out to set up for her. (as a side I got no sympothy to falling, just a lot of concern for the dead telescope)

I was reluctantly persuaded to buy and construct a 2.7m Pulsar observatory.

The construction went very well damp coarse installed concete base and centrall block to isolate the central pier from the concrete base foundation that bears the outer obersvatory walls. I then fitted a raised floor construction of wood and topped it with plywood and carpeting to stop cold rising upwards, All is now complete. The replacement telescope has been installed onto a fixed central pier and all apears to work very well.

However I seem to have a problems with the mount and telescope mirror gather condensation., there is no water ingress into the observatory.

Has anyone exprienced similar problems?

How do I overcome this problem?

Hoping for some useful advice.

Best regrads

mattifor

[mattifor]

not realy sure that I have posted this in correct section.

should it have been in observatory section?

If so can a Moderator move to correct section please?

[arad85]

Moist air and cold metal = condensation. Just because you are in an obsy doesn't stop the problem.

If the problem is during observing then you need dew prevention systems. If you are worried about it when the equipment is not in use, then you need something to wrap around the affected parts that will both keep the metal warmer and avoid any moisture to condense out of the air.

[Merlin66]

I have a 12" Lx200 installed in my Argos Tin Shed Observatory, and find that a heated dog bed blanket ( from Maplin) is ideal. Its about 1m x 1m and has a 12V heating strip system. Gives out about 30W.

I just throw it over the scope and leave it on all the time.

[Helen]

I bought a couple of caravan dehumidifers (cost about £15 for 2 I think) which seem to be doing the trick. They have a coloured indicator for when they can't absorb any further moisture, but you just plug into the mains to recharge and then they are ready for reuse.

Helen

[steppenwolf]

This is a common problem as Arad85 has explained. I have a Pulsar dome and I use a Desiccant type dehumidifer and this keeps my dome interior's humidity level at between 48% and 56%. I was getting due on all the metal bits and nearly had a fit when I saw it - no problem at all now and with a permanent drain to the outside it is a 'fit and forget' exercise.

[mattifor]

Thank you all so much I was getting desperate thought I had missed something in the design.

Off to the shops again then, some realy good sugestion

Thanks again.

mattifor

[steppenwolf]

Be aware that the 'normal' refrigerant de-humidifiers will not work in the cold of winter - if you must have a refrigerant type, it MUST be one of the 'warm defrost' type. This is why I eventually went for the desiccant with oven type as it will work to below freezing.

Good luck.

[afm038]

Steve,

Do you have the make and model of the desiccant de-humidifier that you use ?

I've been looking round for one to use in my dome but the market place seems confusing to those not up to speed in these things.

Many thanks, Andy

[mattifor]

I have a 12" Lx200 installed in my Argos Tin Shed Observatory, and find that a heated dog bed blanket ( from Maplin) is ideal. Its about 1m x 1m and has a 12V heating strip system. Gives out about 30W.

I just throw it over the scope and leave it on all the time.

Thanks Merlin66, It apears that Maplin do not do this any more, been through all their web site. but it sounds like a good idea being 12v could run off a power tank.

[mattifor]

ordered two of the caravan humidifier.

They are rechargable by pluging into the mains when red light shows.

Also have been looking at one of the yacht humidifiers but would need mains power for that, only have 12volt supply at present in the obs.

found some 1m x 1.2m heated travel blnkets to try merlin66 idea also.

there is a lot of monies worth inveted in the Obs and fitting shame to skimp and not prevent the condensation.

[Merlin66]

Glad to see you found them.

Can you share the dtails of the suppliers you found???

[steppenwolf]

Sorry for the late reply (too late in fact as you have purchased already) but had an emergency with my father yesterday that occupied the whole day and evening!

In case it is still of interest to you or anyone else, This is the one I have and it is superb!

[mattifor]

Glad to see you found them.

Can you share the dtails of the suppliers you found???

It was on e-bay dont know if links are allowed but it is item number # # 120452910214 # #for the dehumidifiers.

item number ## 230362506688 ## Large 12v Heated Travel Fleece Blanket

marine dehumidifier item number # #390076402635 ##

mattifor

[afm038]

Steve,

Hope all OK with your dad.

Many thanks for the link, I now know what I'm after. Not so sure about drilling a drainage hole for pipe through dome though. Do you run it on a timer or at a set RH ?

Thanks, Andy

[TedCrampton]

Hi, very interesting as I have e same condensation problem with a nice new pulsar dome.

There is an air gap around the bottom of the rotating dome , necessariyly, so does the dehumidifier work ok in spite if this and is it on 24 hours a day or on a timer as per another comment and what setting (40%, 50% or 60%) do you run it on?

 

Many thanks

ted

[ampleamp]

Hi Ted,

a very old thread indeed! ;-)

Nothing is sealed in this game, nor would want to be imo. I don't have a Pulsar, but a POD, but should be the same principle. I drain my dehumidifier through a small hole in the wall as per Steve above. I tend to have it on a timer for night time use (unless i can actually use the POD!) and only very rarely during the day dependent on weather conditions. This seems to have a happy medium between effectiveness and costs and the only real downside is when it freezes for a few days and then the pipe blocks as the dehumidifier can only store so much water. I got mine from here - http://www.dry-it-out.com/dehumidifiers/observatories - and have an ECO DD322FW, but it is pretty old so model number has probably changed.

 

 

[steppenwolf]

I have the latest style Pulsar domed observatory and I still use the desiccant de-humidifier to very good effect - zero rust in my observatory and I NEVER dew up as the dome acts as a sacrificial dew catcher!

I run mine 24/7 set to 60% and accept that there is a cost in doing so!

[sloz1664]

2 hours ago, steppenwolf said:

I have the latest style Pulsar domed observatory and I still use the desiccant de-humidifier to very good effect - zero rust in my observatory and I NEVER dew up as the dome acts as a sacrificial dew catcher!

I run mine 24/7 set to 60% and accept that there is a cost in doing so!

I do the exactly the same in my Pulsar Dome. Small price to pay for keeping the equipment in good shape.

Steve

[Guest]

On 01/08/2009 at 16:01, steppenwolf said:

Sorry for the late reply (too late in fact as you have purchased already) but had an emergency with my father yesterday that occupied the whole day and evening!

In case it is still of interest to you or anyone else, This is the one I have and it is superb!

Hi all. I have recently built myself an observatory and used a pulsar dome to which I am getting horrendous dew problems inside the dome walls. The scope and pier etc are fine, no condensation at all but the dew is running off the dome walls and I'm having to mop up which isn't ideal. That link you kindly attached takes me to a page of 3 units but I can't see any of them saying they work below zero like yours. Can you tell us your model please Steppenwolf?

Thanks in advance, 

Lee.

[alanjgreen]

I use this Ecoair in my obsy

Ecoair DD122FW SIMPLE 7L Desiccant Dehumidifier with Rotary Humidistat up to 4 bed house 2 year warranty

https://www.appliancesdirect.co.uk/p_dd122fw-simple_ecoair-dd122fwsimple-dehumidifier/version.asp?refsource=APadwords&refsource=apadwords&mkwid=spBLEghnT_dc&pcrid=291303668836&product=DD122FW-SIMPLE&pgrid=57444878046&ptaid=pla-458152214320&gclid=EAIaIQobChMI9JCi-t_n3gIVzLXtCh2IvwsJEAQYASABEgLlJfD_BwE

It works well all year around but you need to empty the water out every 3 days unless you connect up the outlet pipe to the outdoors

Shop around as you can get better price!

Alan

[Hallingskies]

On 31/07/2009 at 10:55, steppenwolf said:

This is a common problem as Arad85 has explained. I have a Pulsar dome and I use a Desiccant type dehumidifer and this keeps my dome interior's humidity level at between 48% and 56%. I was getting due on all the metal bits and nearly had a fit when I saw it - no problem at all now and with a permanent drain to the outside it is a 'fit and forget' exercise.

Just a word of caution on the permanent drain.  I did the same and it froze, and the water backed up and leaked over the floor.  Fortunately it was less than half a litre but it meant I had to mess about lifting the foam tiles, mopping up and drying them out.  During the winter (which has just started, it seems), I go back to using the catch tank.  It can usually go three or four days, even during damp weather. It does mean you have to remember to check inside every couple of days but that’s no bad thing. I have a tiny 300W enclosure fan heater set to come on at 2’C to just keep things above freezing in there as well.  Seems to work.

All great if you have power in your obbo, of course...

[steppenwolf]

2 hours ago, LeeRich said:

Hi all. I have recently built myself an observatory and used a pulsar dome to which I am getting horrendous dew problems inside the dome walls. The scope and pier etc are fine, no condensation at all but the dew is running off the dome walls and I'm having to mop up which isn't ideal. That link you kindly attached takes me to a page of 3 units but I can't see any of them saying they work below zero like yours. Can you tell us your model please Steppenwolf?

Hi Lee,

Either this one or this one will be suitable as there won't be any humidity problem at 0 degrees C - but it is important have one that operates down to a very low temperature and that means getting a desiccant rather than refrigerant type. The one recommended by Alan looks like the first one I recommend and at under £130.00 they are a good price. Allow for continuous drain by running a small bit of pipe through the wall of the dome - I use a plastic tank coupling similar to this

 

[Hallingskies]

On 18/09/2017 at 15:37, TedCrampton said:

Hi, very interesting as I have e same condensation problem with a nice new pulsar dome.

There is an air gap around the bottom of the rotating dome , necessariyly, so does the dehumidifier work ok in spite if this and is it on 24 hours a day or on a timer as per another comment and what setting (40%, 50% or 60%) do you run it on?

 

Many thanks

ted

I reduced the gap between the dome base and wall with some foam rubber P seal from Toolstation.  It doesn’t provide any significant resistance to the dome rotation and certainly reduces the draught through the gap.  I also put some foam seal around the edges of the shutter as well.  It cut the amount of time my dehumidifier was running by about half.  I found the controller on the dehumidifier to be a bit crude so I run it through a Stego humidistat which controls nicely at +/- 5% either side of your set-point (I use 60%).  The Stego is about £50 from RS - a bit pricey maybe but it really helps to keep running to a minimum.

[Guest]

Thanks people, I just ordered the next model up (MK5) from the basic one as it's on offer ?

https://www.appliancesdirect.co.uk/nav/fts/dehumidifer/fts/brd/ecoair

My dome side of the obsy is well vented to, in theory aid an equal temp between inside and out to reduce thermal waves, are you suggesting I should reduce the air flow When the obsy is not in use? This would mean having to let the scope and internal air temp reduce before use and that sort of defeated the object of an obsy for me ? ??

Apologies Mattifor for butting in on your thread mate ?