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Skyshed Pod experience

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#26 YetAnotherHobby

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Posted 13 November 2012 - 12:41 PM

I replicated this PZT design from a fellow CloudyNights member. I bought the quick release brackets from Skyshed, and it works very well. One thing I like about this design over the plywood variety is that it won't accumulate much snow. The downside to the design is if you aren't careful to keep the dome more or less centered and perpendicular to the tracks the dome could fall. To guard against this I used 2x6s for the side tracks with a 2x4 "retaining wall" on the side to limit dome travel. The "tracks" are a fraction of an inch lower than the dome, so you just need to nudge the dome up and back a bit for the clamps to clear the rollers - it's actually very easy because you are never lifting a significant portion of the dome's weight at one time. I lift and push each end separately, which also tends to release the center latch. Once it's on the slides it is an easy shove to get it clear. To put it back in place is just the reverse, although with a little more jockeying from side to side to get the dome back on the rollers. But none of the motions requires much in the way of strength. It would probably be easier with the ramps, but I don't have any problem with it as-is. I still get the light blocking to the north where I need it, and I now have full zenith access in just a couple of minutes.

Geoff

#27 fred1871

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Posted 24 November 2012 - 08:42 PM

The PZT looks useful for those wanting to see more sky, including the zenith, but I think Jim W (above, a few weeks back) summarised the issues with the POD pretty well.

I've not had significant leakage with mine, but I did buy the insulated cover because my Summer in Australia is not like Summer in Canada. Today, late Spring, the temperature was 29C (~85F) by 11am Sun Time and my refractor telescope tube was hot not warm to the touch because I hadn't put the cover on last night. The cover helps, but on the hottest days I still have to take down the OTA to avoid cooking it. Which I did this morning. On the wooden floor above the ground that my POD sits on, far less heating.

This for me is the biggest problem by far with the POD. I can live without the zenith, or get a PZT and hope my back holds up - but the heat issue is very troublesome. Taking down an OTA isn't too bad given the two scopes I have are around 9-10kg each for the OTA - but it wouldn't be possible if I upgraded to a Meade 12 or a C14 for example. They would fit in the dome, but the weight isn't practical for me for taking down and setting up. Too much weight. That's one reason I got a dome, to give up weightlifting.

Otherwise - having a dome is great. Best thing ever for regular observing. And the POD is just big enough (I'm not tall, at 5'9"). I have the 2-bay version so I can store stuff off the floor.

Where I am, the ExploraDome isn't an option due to cost - the big enough version plus freight across the ocean equals a second mortgage. But I'd love to have that level of insulation from heat. That's my major problem with the POD. The insulated cover reduces but doesn't solve the problem.

#28 mclewis1

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Posted 24 November 2012 - 10:05 PM

To effectively deal with the heat trapped at the peak of the dome in a POD I think you need to do two things:

1) Keep as much heat as possible out of the dome - this is where the insulated cover comes into play.
2) Circulate or better yet circulate and introduce cooler air. A small fan moving air from the waist level to the peak of the dome makes a real difference. Introducing cooler air (either from a cool air "sump" or from an air conditioning unit) makes a huge difference.

On really hot days I pull cooler air from under the deck my POD sits on (using a small bathroom style ventilation fan), on most summer days I just keep a small portable fan running.

Without any ventilation the temperatures at the peak of my POD dome were over 50°C on the hottest days, with just the circulation fan running I generally see worst case temps in the 35°C range, and with the cooler air being blown in the temps run about 5° cooler than that.

#29 fred1871

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Posted 25 November 2012 - 04:33 AM

Thanks for the suggestions, Mark. I'll try something like that - pulling cooler air from under the platform (which is how I'm set up as well, on a wooden platform) sounds useful.

That you can have temperatures of 50C or more in a CAnadian climate is impressive in a negative way. Australian Summers are hotter than you get so my POD might hit 60C on the worst days without help, and over 40C with the insulation cover (outside, shade temperatures of 35 are not rare, and sometimes it reaches 40C). So there's a clear need for cooling and I don't want to install A/C. That's a last resort.

Thanks again for the ideas on how you use the fans.

#30 mclewis1

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Posted 25 November 2012 - 09:37 AM

Fred,

Yes, we don't normally talk about temperatures in the 50°s around here ... lol. Those 50°C numbers I measured came on a couple of days where the reported daily highs were in the low 30°s C (high 80°s F). They were measured right at the peak of the dome using a remote sensor from a home weather station, it was velcro mounted to edge of the secondary dome. There may have been some heat transfer from the actual dome itself but the air temperatures were not much different. At the same time the temperatures 12" lower (around the top of the scopes) were in the upper 40°s C. So it's probably safe to assume that on sunny days with no air movement within the dome that someone could see a 15°C difference between the outside and inside temperatures.

#31 Startraffic

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Posted 25 November 2012 - 10:28 AM

Fred,
I'm the 2nd-3rd owner of an XL3. The last owner install a 10" attic fan & thermostat that come on at a user set temp in one of the bay sides with louvers on the side of the bay. It works great now. It had considerable problems with leaking. I made an aluminum "awning" & rubber gasket siliconed & screwed above the louvers & sealed the louvers themselves. Since I sealed it up no more leaks & the fan can be allowed to do it job of cooling off the dome itself. I put a 7 drawer tool chest (http://www.harborfre...hest-68785.html) in the same bay for storage. Works like a champ. Temps don't get above ambient. It won't help much if your ambient is 105*f though. Some kind of sunscreen is your only real option. The highest ambient temp I get is ~105*f on the hottest summer day.

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#32 wolfman_4_ever

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Posted 25 November 2012 - 03:07 PM

Absolutely love my pod!

#33 fred1871

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Posted 26 November 2012 - 07:31 AM

Thanks, Startraffic - useful ideas.
I'll be checking out the best fan arrangements this Summer. Your arrangement sounds good. :)






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