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Condensation on mount and what I did to fix it


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#1 w0mbat

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Posted 25 June 2013 - 02:18 AM

Hi all,

I recently finished building my observatory and mounted my new DDM60Pro on the pier for the first time. As soon as I was ready to start initial polar allignment a long period of cold wet weather happened. We had 250mm of rain and I was very pleased that there was no sign of any leaks in the observatory (a Sirius 2.3m). Then the sun returned but temperatures remained low. It was at this point that I entered the observatory during the day and was alarmed to find the entire pier and mount wet with condensation. I realised that with the sun warming the observatory walls that the mount and pier were now the coldest part in the building and thus were collecting the atmospheric humidity as condensation.

I decided that if I was able to raise the temperature of the mount slightly that this may solve the problem.

So I have made a small heater to sit inside the mount on the baseplate. I soldered three 68 Ohm 9 Watt wire wound resistors in parrallel and placed them in the bottom of a diecast metal project box and half filled the box with epoxy resin. I attached an old scanner power supply (measured at 14.3 volts). So with around 23 Ohms and 14.3 V we get just under 9 Watts. I then added an LED to indicate that the heater was running as it is not possible to feel any warmth when the heater is in position as the mount conducts the heat away so well.

I am now running this heater continuously and, so far, it seems to be working. By touch, the mount is just slightly warmer than the pier and although some condensation still collects on the pier, so far the mount has remained dry.

Ian


ASA DDM60Pro, ASA N10 Astrograph, Orion ED102T CF Refractor, Canon 60Da DSLR, Sirius 2.3 Metre Observatory, WIN10 Pro 64bit.


#2 unger61

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Posted 08 October 2013 - 12:13 PM

Hi...

 

I got pretty much the same setup as you... I encountered severe condensation in the dome as well. I did order the dome

with the "solar vent" which is Sirius' terminology for a quite dear fan operated during the day via a small solar panel. During

production they forgot to fit the fan. I received the unit some weeks later and fitted it. The difference was absolutely remarkable.

No condensation anywhere in the dome and on the equipment. If you haven't got a fan installed you should seriously think

about it.


DDM60, Officina Stellare 152mm Apo, QHY9 CCD, Imaging Source DMK41, Sirius Dome


#3 w0mbat

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Posted 08 October 2013 - 11:07 PM

Hi,
Thanks for that info. I did wonder if I should have ordered the solar vent. I would be very interested to see some photos of the solar vent and where/how it is installed. I am thinking I could probably build a similar device for less than what Sirius asks. I am very happy with my Sirius observatory but I did find it hard to find information on the various options when I was ordering. I had assumed the main purpose of the ventilator was to remove hot air in the summer. It did not occur to me at the time that condensation would be such an issue.
If you could post some photos it would be great.
Thanks
Ian

ASA DDM60Pro, ASA N10 Astrograph, Orion ED102T CF Refractor, Canon 60Da DSLR, Sirius 2.3 Metre Observatory, WIN10 Pro 64bit.


#4 unger61

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Posted 09 October 2013 - 09:17 AM

Hi Ian

 

The vent sits in a cubeshaped fibreglass mount that has a flange on the bottom so that it fits exactly to the

curvature of the dome. The small solar panel sits on top of the stainless fan housing.  All I had to do is to drill a

10cm hole in the dome with a hole saw. One of the off the shelf hole saws with a pilot drill in the middle works

perfectly. Even though it hurts a bit to drill a hole in a pristine dome... I installed it a a foot or so from the top so

that the fan sits level. It has some stainless sleeves which prevent rain getting into the dome. The little unit runs

all day when there is daylight. Even though it's so small it make a huge difference and I have now zero condensation

in the dome. I think you can build something similar for half the price.... I think that is important to choose the

location right in order to allow for good air circulation.

 

Cheers

 

Clemens

 

Solar vent on Sirius dome
Solar vent on Sirius Dome

DDM60, Officina Stellare 152mm Apo, QHY9 CCD, Imaging Source DMK41, Sirius Dome


#5 w0mbat

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Posted 09 October 2013 - 12:35 PM

Thanks very much Clemens. It looks to me like the only tricky bit would be the spherical profile to match the dome. Otherwise easy.
Ian

ASA DDM60Pro, ASA N10 Astrograph, Orion ED102T CF Refractor, Canon 60Da DSLR, Sirius 2.3 Metre Observatory, WIN10 Pro 64bit.


#6 Waldemar

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Posted 09 October 2013 - 06:23 PM

Thanks very much Clemens. It looks to me like the only tricky bit would be the spherical profile to match the dome. Otherwise easy.
Ian

A nice piece of plastic foil to cover the dome, big enough to prevent messing up with the following materials:

A sheet of thick woven glass fibre, resin and hardener..

Be sure the plastic is on the dome without wrinkles; use tape to secure it in place;

lay the fibre sheet on it and use the resin according directions, Make it as thick as you think is useful.

When it is hardened you can shape this as you like and use this as a base plate for further construction...

 

Maybe that works for you :-)

 

Regards,

Waldemar


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Mount: DDM85 Standard 12V ; Telescopes: TEC140 + 140FF + Quad TCC ; Celestron RASA; TMB 92SS + 27TVPH Cameras: ZWO ASI 174MM cool; SBIG STF8300M; ATIK4120EX; TRIUS SX-36
Filters: Astronomik and Baader NB + RGB; Lunt double stack 75 mm unobstructed signature series + BF 3400; Dutch weather and light polluted skies.  

#7 GeorgeCarey

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Posted 13 October 2013 - 09:30 AM

Does the fan draw air into or out of the observatory?
Does it only run during the day?
My observatory used to get bad condensation over the night, so in the morning everything would be wet.
I installed a dehumidifier and sensor which keeps the RH below 65%.
So far this has worked very well, but it does cost money for the electricity.

ASA DDM60Pro, homemade 8" and 10" reflectors, QSI 683 camera, Astrodon 5nm filters, Pulsar dome observatory. Website: http://www.geoastro.co.uk


#8 unger61

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Posted 14 October 2013 - 01:31 PM

Hi George

 

The fan draws air aout of the observatory and runs via its built in solar panel only during the day.

Even though it's just a little unit it does an amazing job. Prior to the installation the observatory interior

was dripping wet. Now its totally dry... I would have never thought that it would make such a

difference.


DDM60, Officina Stellare 152mm Apo, QHY9 CCD, Imaging Source DMK41, Sirius Dome


#9 GeorgeCarey

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Posted 14 October 2013 - 03:18 PM

Thanks,

I see that you are in Australia. I wonder if such a fan would work in the British climate?

I would be reluctant to cut a hole in my dome and find that it didnt work!

I might try an experiment by making a replacement lower shutter and putting a fan in that. 

The lower shutter acts like a drawbridge and swings down and out when the dome is in use.

 fan.jpg


Edited by GeorgeCarey, 14 October 2013 - 03:19 PM.

ASA DDM60Pro, homemade 8" and 10" reflectors, QSI 683 camera, Astrodon 5nm filters, Pulsar dome observatory. Website: http://www.geoastro.co.uk


#10 unger61

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Posted 18 October 2013 - 04:26 PM

Hi George

 

Like Ian I am based in Victoria where the weather can be rather diverse...and at times quite British... :)

I can understand your hesitation to cut a hole in your pristine dome. I felt exactly the same when I installed

the fan in the Sirius dome which is identical to your dome (i.e. fold out section below the shutter). I believe

the higher a fan is mounted in the dome the better the effectiveness and air circulation. I know of another

Australian amateur and ASA user with a number of Sirius domes who resides near Cairns in tropical Queensland

who employs two fans per dome. If it works there it should work under your conditions as well. Have a look

at the links below.

http://www.astronomy...590/image/3516/

http://www.astronomy...ge/3517/id/590/

 

Cheers

 

Clemens


DDM60, Officina Stellare 152mm Apo, QHY9 CCD, Imaging Source DMK41, Sirius Dome


#11 nakbrooks

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Posted 18 October 2013 - 04:59 PM

I notice he has fabric stretched over the trusses. What are the benefits of that? As he (like me) is in a dome I guess the increase in wind resistance wouldn't be a downside.
Nigel Brooks
Stratis Observatory, Hautes Pyrénées, France.
http://www.facebook.com/stratisobservatory

#12 unger61

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Posted 21 October 2013 - 01:08 AM

Not sure why the fabric is used. I could imagine that it is for dust protection and keeping stray light out. It is a very professional setup...


DDM60, Officina Stellare 152mm Apo, QHY9 CCD, Imaging Source DMK41, Sirius Dome


#13 Waldemar

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Posted 21 October 2013 - 03:45 PM

I would like to keep bugs out of there as well...


Waldemar
--------------
Mount: DDM85 Standard 12V ; Telescopes: TEC140 + 140FF + Quad TCC ; Celestron RASA; TMB 92SS + 27TVPH Cameras: ZWO ASI 174MM cool; SBIG STF8300M; ATIK4120EX; TRIUS SX-36
Filters: Astronomik and Baader NB + RGB; Lunt double stack 75 mm unobstructed signature series + BF 3400; Dutch weather and light polluted skies.  

#14 nakbrooks

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Posted 21 October 2013 - 04:24 PM

Yes, I have spiders spinning webs between the trusses.
Nigel Brooks
Stratis Observatory, Hautes Pyrénées, France.
http://www.facebook.com/stratisobservatory




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