SkyShed POD vs. Thinking Outside SmartShed
Last spring when I decided I was finally going to go ahead with building an observatory, a Canadian company called SkyShed announced their plans to produce an inexpensive plastic observing dome, the SkyShed POD (Personal Observatory Dome) and called for beta testers. I immediately replied, but like about a thousand other people, wasn't selected.
Since I wasn't selected to test, I went with Plan B and purchased a SmartShed Deluxe by Thinking Outside at my local Sam's Club. I did a lot of research online about converting a storage building to a backyard observatory, and the SmartShed kept showing up. But I always had a nagging question: Did I make the right choice?
It turns out fellow Dam Astronomer Andy Raiford did make the cut to test the POD, and it recently arrived in his back yard. I went for a visit and made some notes comparing his POD to my SmartShed.
There's no denying it: the POD is cool-looking. You know when you see it that you're looking at an observatory. SkyShed got the proportions right and built a handsome building.
My SmartShed? Well, it's not unattractive--I think it looks a whole lot nicer than most storage buildings--but it doesn't look like an observatory. But is that a bad thing? The POD just screams, "Hey! There's a telescope in here!" while the Smart Shed doesn't say anything at all. Call is security through obscurity, but I don't mind not drawing attention in my suburban back yard. Let's call the outside looks a draw.
Seeing the Sky
SkyShed made an interesting decision building their dome. Rather than follow the traditional design of a slit along one side of the dome, they chose a clamshell design. The dome is split down the middle and pivots open at the base, opening up the whole hemisphere. It's cleverly done, and eliminates some dome drawbacks. There's no need to rotate the dome during an imaging or observing session to keep a slit aligned with the telescope. You can also stand in the building and see a big chunk of sky instead of just a sliver. The downside to a clamshell design is that unless you offset your telescope from the center of the dome, you can't point it straight up at the zenith. There's a lot of online debate going on about this: Some see it as a major drawback, as the zenith is the best place to observe in the sky as you're looking through the least amount of atmosphere. Others feel that the obscured portion of sky is too small to be of consequence, and that you can't image at the zenith with a German equatorial mount (GEM) anyway due to a situation called "meridian flip."
The SmartShed roof opens differently. It's also in two pieces, but rather than pivoting on a hinge, one half is lifted up and slides over the over. The building wasn't designed to have an open roof, but it's a happy feature with the way Thinking Outside put it together that it works without modification. The open roof does interfere with part of the sky though--I lose views to the north below about 25° elevation. East, South and West can be accommodated to the horizon by opening a door, but in my back yard the sky is obscured by houses before the walls become an issue.
After looking at both setups side-by-side, I think I prefer the SmartShed's opening. It does take a little more effort to unscrew four connectors and slide the roof off, and realigning everything at the end of the night and putting it all back together takes more time than simply swinging the dome closed, but I like the big view of the sky. I also don't have to think about offsets or turning the dome to any particular direction.
Controlling the Elements
I see having a backyard observatory as serving two purposes. It allows you to permanently mount a telescope so that it's available any time the sky's clear. You can simply open the roof and begin observing. The other reason is to control the elements--wind, cold and light. WInd and cold are related (duh), but even on warmer nights wind can present a challenge to observing or photography as it tries to push your telescope around. And while an observatory can't do anything about skyglow from urban lighting, it can shield you from the neighbor who insists on leaving his back porch light on all night.
I'll admit up front I haven't spent a night observing in a POD, but I have a pretty good imagination. I don't see the clamshell offering a whole lot of protection from the wind. The way I see it, unless the wind is coming directly from behind the open dome, the open half is going to act like a funnel and capture every breeze. As for the neighbor's porch light, the relatively low walls won't block much light from your eyes. This is where a traditional dome would have an advantage with its smaller opening.
The SmartShed has remarkably good protection from the elements despite the open roof. The high walls do a good job of deflecting most of the wind, and completely block all outside light when I'm sitting down. I find I can get as dark adapted as the skyglow will allow, and there is no white light showing in any direction. I think I can stay warmer inside too, by staying under the covered section.
There's no contest here. The SkyShed POD is a seven-foot diameter circle with about 38 and a half square feet of floor space. The SmartShed is a seven-by-eleven foot rectangle with 77 square feet of floor--more than double the POD's. The rectangular elevation of the SmartShed means more headroom, too. The POD can be equipped with bays to increase the covered storage, but unless you crawl, you can't actually get in them. Even with a table and an observing chair there is still plenty of room for two adults inside the SmartShed. The SmartShed also comes standard with built-in adjustable shelving.
A second major interior difference is the floor. The POD is intended as a portable building, and does not include a floor, unlike the SmartShed's full floor. No floor is an advantage for using a tripod, but I like having my pier coming up through a hole in the floor. I just don't see the need for a portable observatory, and you'll need a full-size pickup or a trailer to move the POD, so I'd rather have a floor. I don't know how weather-tight the POD is, but I can say that my SmartShed has never leaked, even during some pretty intense thunderstorms. I wouldn't want to leave anything on the ground inside the POD. I imagine there's going to be a lot of seven-by-seven decks built below PODs. The POD and the SmartShed are built from similar materials and can be assembled in roughly the same amount of time.
The Bottom Line
Regular price for a SkyShed PODis $1,495, with shipping to my door in Texas an additional $664. Shipping to other states varies from $365 to more than $900 to the Florida Keys.
A Thinking Outside SmartShed Deluxe is $795 at Sam's Club. I picked mine up at my local store, so there was no shipping costs. The Sam's web site estimates $267 shipping to my ZIP code. The only modification required for using the building as an observatory was cutting a 12-inch hole in the floor with a jigsaw for the concrete pier to protrude through.
I don't have that nagging question any more. The POD is cool, no doubt, and SkyShed should sell a lot of them. But in my opinion, the Thinking Outside SmartShed Deluxe is more useful and a better value.
Be sure to read the comments for Andy's rebuttal. He has more experience with the POD, and I appreciate his feedback, particularly concerning the floor and wind.