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Observatory Dome question

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#1 geewizard

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Posted 01 August 2011 - 07:31 PM

I observe in interior Alaska where, during the winter, it gets REALLY cold. I'm considering a SkyShed POD but I really wonder if it would help me at all. Sure, it would keep the snow off the telescope but that's about it. Heat will just distort the viewing, I think.

Or, as a newby, am I missing something?

#2 piaras

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Posted 01 August 2011 - 08:52 PM

I have used a POD in winter but it is not as cold you can get. I found that it is slightly warmer inside as one is sheltered a bit. If you use electric socks to keep your feet warm, you could likely observe more into the darker periods. With an insulated POD who knows. Others may have better ideas like a warm room etc.

#3 Hilmi

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Posted 01 August 2011 - 11:42 PM

Geewizard,

I have heard that the dome opening, due to it's large size would release a lot of the pent up heat really fast. When I was looking for reviews of the POD, I did not find anybody complaining about the heat hurting the viewing. The only criticism I found was from the book called "Setting up a small observatory" And the comments in the book were written by somebody who clearly stated that he had not tried the product and that he is making assumptions.

#4 Bob Griffiths

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Posted 02 August 2011 - 07:12 AM

Geewizard:

I run a 8 foot Exploradome...BUT sure do not live in Alaska..and I stay in the house when the outside temp gets down to single digits ... The Pod is basically half open to the sky unlike a roll off which is usually fully open to the sky...so I honestly do not see thermals from being a major problem..at least until then temps drop way down below zero F... and then only if you image ...

I do not image...and inthe 5 years I have had my slotted dome have never ever..not even once been bothered by thermals and I wear heated motorcycle clothing in the winter..(full sleeved heated jacket LINER..socks and glove liners...and I wear a hooded sweat shirt over the jacket liner...Set the temp on the clothing at 100 degrees..and still have never seen thermals...

NOW a Camera may..especially if it is really really seriously cold ...

Bob G,

#5 Mirzam

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Posted 02 August 2011 - 06:56 PM

My experience with an aluminum dome over the past two years has been an eye opener. The dome interior is probably 10 degrees or more warmer than the outside air, or at least it feels much warmer. The reason is that a clear sky is very cold (-60 C) and when you radiate to a cold sky you radiate heat away very efficiently. Inside a dome you are shielded from the sky and the radiative cooling is less efficient.

Similarly, dew formation is generally not a problem inside the dome, or at least not until near sunrise, when a little dew may begin to form.

As far as thermal distortion of images, I would not recommend a dome where rapid and ideal thermal equilibration is needed. But for viewing DSO's, I open the dome an hour or two before dark and have never felt like thermal effects were a serious problem.

If thermal considerations are critical an air conditioned dome may work well.

JimC

#6 geewizard

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Posted 02 August 2011 - 07:38 PM

It will be at least -10 and as much as -30F when I observe. Or maybe I just won't at those temps. It would cut off a large amount of viewing time if I didn't go out at those temps.

And I'm just wondering if a dome would give me any advantage. We normally have very still air at those temperatures. But even the slightest breeze, even a tiny downslope air movement, will be felt. So, a dome might help there.

I appreciate your thoughts.

#7 Startraffic

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Posted 03 August 2011 - 05:18 AM

geewizard,
I just got my POD and have only had it up a few weeks. I can tell you that the amount of time saved by having my gear already setup & ready to go is a HUGE timesaver, & I haven't even seen any cold yet. I think that's where having a dome is a big advantage.

StarT :cool:

#8 Wouter D'hoye

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Posted 03 August 2011 - 05:42 AM

Hi,

The main goal of an observatory is saving you the time and effort of setting up each time. And added to that shed you from wind, weather and light pollution.

Essentially in the observatory temperatures should , and most likely will, be equal or very near so to the outside temperature.

Though due to the protection of from wind the temperature inside an observatory will feel more comfortable.

Anyway, during your Alaskan winters I guess it will get pretty darn cold at night ;)

#9 Mirzam

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Posted 03 August 2011 - 08:17 AM

As I tried to indicate before--a dome will be very helpful. You will have wind protection and radiative screening. Of course at -30F your clothing strategy will be a big factor too. Another plus for domes is the relative ease of snow removal. I have both a roll-off and a dome.

JimC

#10 nytecam

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Posted 05 August 2011 - 05:42 PM

My experience with an aluminum dome over the past two years has been an eye opener. The dome interior is probably 10 degrees or more warmer than the outside air, or at least it feels much warmer. The reason is that a clear sky is very cold (-60 C) and when you radiate to a cold sky you radiate heat away very efficiently. Inside a dome you are shielded from the sky and the radiative cooling is less efficient.

Similarly, dew formation is generally not a problem inside the dome, or at least not until near sunrise, when a little dew may begin to form.

As far as thermal distortion of images, I would not recommend a dome where rapid and ideal thermal equilibration is needed. But for viewing DSO's, I open the dome an hour or two before dark and have never felt like thermal effects were a serious problem.JimC

Agreed a metal roof does get hot in sunshine but cools very rapidly at sundown - insulation can trap and delay the cool-down :o I only image and have not had any thermal effects through the slot [in 30yrs with two domes as avatar] and it seems warmer inside because of protection from windchill etc. Of course I'm in UK and not Alaska but still dome's the way to go ;)

#11 geewizard

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Posted 08 December 2013 - 10:48 AM

Update:

I have moved to Spokane, Washington! Much warmer place to view.
I am still in the market for an observatory. Would any of you care to compare the SkyShed POD and the Exploradome? Seems to me that slot in the Exploradome would fit me better in that it will help with the light pollution.

Comments appreciated!

#12 Startraffic

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Posted 09 December 2013 - 05:46 PM

geewizard,
Well, I still have my POD XL3, but... this upcoming spring I'll be replacing it with an upgraded 10ft Homedome. More interior space, Dome rotation, Shutter automation, etc. There will be some overlap with the POD & HD. I'll be operation the G-11 in the POD & the HGM in the HD. Once the HGM is really working well, the G-11 & POD go on the market.

The single biggest issue I've had with the POD is that I haven't been able to solve the leaking at the hinges. Water migrates down into the bays & drowns whatever is in there. Try as I might I haven't found the right spot. SWMBO has said "Get rid of it, or get out of astronomy!" I'm not getting out. A deal for the HD came up & I grabbed it this past summer.
I still haven't had the time to put it up. Multiple home improvement jobs got in the way this year, new windows, house insulation, siding, replace the house wiring, etc. Nothing trivial. LOL I'm still digging my way out. This spring the HD gets a 11ftx12ftx18in deck & a pier.

The previous owner of the HD is Mike Reilly & he was very happy with it. I hope to be. It should be in place for another 4-5 years until I retire then I'll take it down & take it with me. SWMBO & I are "discussing" where we're going. She wants to stay in MD. Bad weather, bad skies, & horrible taxes. :vomit: I'm done with that. Somewhere with clear dark skies (Bortle class 2-3), warm weather with little or no SNOW! :shrug:

Clear Dark Skies
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#13 Midnight Dan

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Posted 09 December 2013 - 05:53 PM

Hi Startraffic:

Just wondering if you saw my thread regarding my SkyShed POD. I had water in one of the bays too and though it was from the pivots. Turned out it was actually from a hole in the side of a pin socket near the *bottom* of the bay section!

Check out the thread here: http://tinyurl.com/mq5x5ce Towards the end, there are lots of pictures I posted about the leak and the fix.

Once I figured it out, the fix was easy and it has been dry as a bone ever since.

-Dan

#14 Midnight Dan

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Posted 09 December 2013 - 06:04 PM

Update:

I have moved to Spokane, Washington! Much warmer place to view.
I am still in the market for an observatory. Would any of you care to compare the SkyShed POD and the Exploradome? Seems to me that slot in the Exploradome would fit me better in that it will help with the light pollution.

Comments appreciated!


Hi geewizard:

I can't compare the two because I only have the skyshed POD. I've only had it for a few months, but so far I love it. The fact that the mount is set up, polar aligned, and ready to go at a moments notice is priceless! So is the feeling at the end of the night when you're getting cold and realize that all you have to do is turn off the power, close it up and walk into the house. Previously, it would be a half hour or more of tearing things down, packing them up, and making multiple trips into the house to put it all away. This while you're freezing cold and can barely feel your fingers.

The POD itself is very versatile. I built a PZT (Pod Zenith Table) for it, which makes it even more so. Thread here:
http://www.cloudynig...d=Observator...
I can push the dome off to the side if I want a full view of the sky, of leave it on to block the wind or nearby lights.

I bought the XL5 model with all 5 bays, and I'm glad I did. The bays don't add all that much to the cost if you buy them at the same time as the POD. But they add a HUGE amount of extra room. The circular interior of these small observatories (POD or Exploradome) can be a little tight for room. There's plenty of room for the mount, scope and one or two people, as long as the interior is clear of other stuff. So you really need those bays for the "other stuff".

The POD seems very well made and MUCH more thick and solid than you might think for a plastic building. See my link in my previous comment for my build thread.
-Dan

#15 geewizard

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Posted 14 December 2013 - 10:02 AM

Thanks for all the comments. Still looking and thinking.

#16 Starhawk

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Posted 16 December 2013 - 03:37 PM

Do you use a exhaust fan to pull air through the open shutter?

-Rich

My experience with an aluminum dome over the past two years has been an eye opener. The dome interior is probably 10 degrees or more warmer than the outside air, or at least it feels much warmer. The reason is that a clear sky is very cold (-60 C) and when you radiate to a cold sky you radiate heat away very efficiently. Inside a dome you are shielded from the sky and the radiative cooling is less efficient.

Similarly, dew formation is generally not a problem inside the dome, or at least not until near sunrise, when a little dew may begin to form.

As far as thermal distortion of images, I would not recommend a dome where rapid and ideal thermal equilibration is needed. But for viewing DSO's, I open the dome an hour or two before dark and have never felt like thermal effects were a serious problem.

If thermal considerations are critical an air conditioned dome may work well.

JimC



#17 Startraffic

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Posted 17 December 2013 - 08:27 AM

Starhawk,
I have my fan pushing air out of a set of screened self closing louvers. Helps keep the bugs out.

Clear Dark Skies
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#18 P26

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Posted 17 December 2013 - 09:59 AM

The good news is that a full dome will protect you from not only wind but from thermal radiation cooling. The bad news is that an observatory's interior must be at ambient temperature or you'll disturb the air in the shutter area, which will produce bad "seeing". There are a lot of trade-offs involved in astronomical viewing.

Posted Image

This photo from my January 2005 observing log reminds me it gets down to 7°F here in RI and I used to have to shovel out the observing site.

In 2006 I built a 10' structure with the very first run of the Exploradomes. That sucka was weather-proof and bullet-proof.
Posted Image
I'm out there all the time anyway, but the convenience of the dome allowed me to segue into astrophotography and eventually into astrometry.

Although I prefer working from the observatory temperature was a relatively cold 17°F the other night so I ran the scope and the camera from within the house using Windows Remote. Given the extreme conditions in Alaska you may wish to consider eventually moving in this direction yourself.

Clear skies,

Pete Peterson
Wishing Star Observatory I15

#19 TimN

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Posted 19 December 2013 - 10:31 AM

I have a POD with 3 bays and I agree with Midnight Dan's comments. Like Dan, I built a PZT to allow it to be used as a roll off. I use my POD mainly for imaging and it allows me to have all my equipment ready to go. I then can start imaging from my POD and then go inside and control everything from there. The POD design allows me to image across the entire sky without intervention. I regularly image below -20C. The POD was my best purchase in astronomy. Allows me to really increase my imaging time at a reasonable cost.

#20 stmguy

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Posted 19 December 2013 - 11:08 AM

Think about using remote control from your house if not too far from your proposed OBS , takes the cold right out of the equation.
Best thing I did in this hobby is build my OBS
Norm

#21 geewizard

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Posted 23 December 2013 - 10:51 AM

All good information. Thanks.

#22 Bill F

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Posted 30 December 2013 - 07:12 AM

I only get down to about 10F, but often associated with high humidity and wind. A dome has a dramatic effect in reducing dew. On many nights before the dome I was de-misting every 10 minutes or so. Now it is about every hour in the same conditions. As long as you choose objects to observe downwind, the dome makes a huge difference to comfort in windy conditions, plus the scope stays steady. The reduction in radiation cooling previously mentioned also makes a big difference to comfort.
I have severe local light pollution, which is greatly reduced by the basic design of a dome, plus my own adaptation to reduce the slot even further.

Best piece of kit I ever bought.

Bill






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