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ExploraDome and POD Domes
Voice your opinion about this subject in our forums
Low Cost Observatories
ExploraDome and POD
Jim Weilsek and Chris Schroeder
Anyone taking more than a casual interest in astronomy has thought of owning an observatory sooner or later. Until recently the only low-cost alternatives have been opened roofed tents, PVC based enclosures or roll-off roofs. It wasn't until recently that the astronomer had a choice of alternatives that provide the security of a roll-off and the functionality of a domed observatory with a relatively low investment.
Three relatively new products are available in this category, the Polydome "ExploraDome", the Skyshed "POD" (Personal Observatory Dome) and the Astrogizmos AstroGazer. This October review will cover the ExploraDome and POD. The Astrogazer will be published in November and there is an addendum on the product at the end of this review.
The ExploraDome was the first entrant, shipping in May 2006. Initially offered as a "dome-only" do-it-yourself project, the product has evolved into complete building kits and a portable unit. According to the vendor they shipped over 100 units in 2006 and 75 so far this year. Thirty units are on order for Europe and 24 units of the round building kit have been sold since April (stats from August 2007).
During this time there have been many improvements in the product including complete building kits, molded black dome interiors, shutter opening and closure cords, dome motorization and ability of the shutter to open beyond the zenith.
The Skyshed POD is the newer entrant into the arena starting production and deployment this summer in a May/June timeframe. The POD is available in several different configurations, from a round unit, to one that incorporates up to 5 equipment "bays". At the time of this writing Skyshed has declined to announce any production or sales information.
Chris and I met via internet/email while we were both looking at low cost observatories. Both of us encountered a lot of information and opinions on the two products, but much was posted by those that own one or the other, (or in some cases neither). Sorting fact from fiction was difficult without first hand experience.
In the end, Chris decided to go with the Skyshed POD and I went with the ExploraDome. When we found out we lived close by we decided to try "Trading Spaces" with our respective observatories and to share our practical observations with others. The advantage is that as owners, we could evaluate both products under field conditions and we could compare notes and share them.
Chris (who was originally on the short list for ExploraDome) purchased a POD which was delivered in July. He primarily does visual observing with an 8" SCT in alt/as mode. His lunar gray POD is set up as a permanent installation and is the XL-3 model coming with three equipment bays.
I was on the short list for a POD but ended up purchasing a green ExploraDome as a permanent observatory in May and purchasing a second ExploraDome as a trailer portable in July. Both were straight "round buildings".
My portable ExploraDome evaluated is white in color with a molded black dome liner and optional rotation motor. Being a portable it is not equipped with "stepouts" (the equivalent of POD equipment bays). I primarily image with a 10" SCT.
In August I delivered my portable ExploraDome to Chris's house and we had the products set up side by side for about a week and a half. As might be expected a two month drought ended the next day and we had a week of rain. Between the raindrops we did manage to get some viewing and observations in as well as compare notes.
Preparing for a review we made a Cloudynights post asking for observatory criteria to serve as the basis for this review. We ended up with about 30 criteria that posters thought important and offer comments to each of the criteria where applicable. In some cases we were able to do measurements and in some cases our impressions will be subjective. We also asked for input from members of our respective astronomy clubs.
Typically these reviews are done in a "shootout" fashion of which product is "better". We've found that which one is "best" really depends largely on the astronomer's personal preferences and uses for the observatory. Both products have their strong and weak points but suit their intended purpose as a low cost observatory fairly well. From a shootout standpoint, in the end both would be "left standing".
Observatory Criteria from the Cloudynights post:
á Dome rotation noise
á Required dome speed rotation
á Sky visibility
á Wind protection
á Dew protection
á Ground light protection
á Dark adaption
á Door size, ease of entry, Ease of getting equipment in and out
á Internal storage capability and expandability
á Obtaining replacement parts
á Automation potential
á Interior temperature from the sun
á Cool down of the dome interior, thermal currents
á Weather/wind/heat resistance
á Wind resistance
á Ease of assembly
á Assembly instruction clarity
á Assembly time
á Product fit and finish
á Dome rotation ease
á Dome rotation smoothness
á Ease of dome/shutter opening/closing
á Human exposure to the elements
á Interior room for moving around the pier/tripod
á Shutdown process at the end of the night
The following pages contain the evaluation criteria and our respective comments about the two products. In some cases the evaluations are subjective but where possible the authors attempted to measure or quantify the findings.
Dome rotation noise
Chris: The noise level is not bad, about the same level as my CPC800 on slewing speed. Both the ED and POD were similar in noise and effort to rotate.
Jim: I found both domes are about same in terms of noise and both are acceptable. If you "rush " either dome it can sound like a freight train, but for normal rotation speeds both are quiet enough not to annoy the neighbors. My ED is also equipped with a rotation motor or can be turned by hand as well.
Required dome speed rotation
Chris: Because of POD's hemisphere opening, the only rotation needed while imaging would be if you are blocking part of view because of stray light. The ED does have a decent sized slit, I did a tour of the objects in Cassiopeia one evening with my CPC800 and only had to move the dome twice in order to see them all.
Jim: The need to rotate the dome depends on the sky location. As an example with M13 passing overhead the dome would need to be rotated 180 degrees as the target passes overhead, but after that nearly parallels the shutter opening. While imaging near the Celestial Equator the dome would need to be nudged about every hour with my 10" SCT. The amount of time between rotations would also be dependent on the aperture and configuration of the scope being used.
Chris: POD; You see a lot, depending on where you are sitting or standing. Towards the back, I would say 120¡ field of horizontal and 70¡ vertical. Up front, well you pretty much see everything. On the first night after Jim and I were done, we stood in the front of the POD and talked for about an hour while enjoying the view of the Milky Way overhead.
ED; like the POD, it depends were you stand, but needless to say the view is more restrictive, but you can stick your head out of the shutter and see quite a bit.
Jim: There is no doubt that you have a better 'connection' with the stars while viewing from a POD. It's like a picture window into space where the ExploraDome offers a smaller slice of the sky.
The POD's clamshell design however necessitates an 8 inch "overhang" of the dome skirt before the zenith and effectively creates a circular "blind spot" to the sky. The size and location of the blind spot would be dependent on equipment and pier/tripod placement the observer wishes to use. If the scope (something like a small dob) can be easily moved to see out from under the dome overhang, or of the user does not wish to view near the zenith this would not be an issue. With a fixed mount or pier offsetting in some direction would be necessary to get out from under the overhang. In some cases POD users have positioned the blind spot in an area of the sky they seldom view, in front of trees or sky-glow.
The vendor also suggests that "in the time it would take to open a roll off roof the POD's dome can be removed". This seems a little drastic to turn the observatory into a roll off, but would offer a clear zenith.
ExploraDome's traditional shutter design opens about 8" beyond the zenith and offers much more flexibility in terms of pier placement and overhead visibility.
The shutter does present a slimmer view of the sky. This is not an issue with a robotic scope but for a user doing visual targeting it is easy to lose your bearings. With no outside reference, more than once I've 'gotten lost' in the observatory. It's funny, sometimes the only way you can 'orient' yourself is by looking at the telescope mount and "determine north".
View from the ExploraDome below. Excellent wind, dew and light protection is evident. The lack of direct sky visibility is as well.
Chris: The POD is more open so you can have more wind depending on the direction is and what you're looking at. Moving the dome to block wind will restrict your viewing in that direction. Conversely, during the warm and muggy nights, I would purposely move the dome to catch the breeze. This worked really well during the daytime, move the dome to block the sun but catch the wind.
Jim: The ExploraDome affords excellent wind protection. The shutter design can often be "buttoned up" to where the opening is just large enough for an OTA. The shutter door consists of two parts. The main door slides over the back of the dome to beyond the zenith and a second lower door flips open offering horizon access. I can feel wind bleeding through the dome/wall joint and coming in the shutter opening, but if I have the door to the observatory closed there is virtually no turbulence inside the dome. Closed up like this, I have been able to image with about ~1 arc second of error nearly into winds blowing 10 to 15 mph. For calmer nights light winds are no issue with the shutter doors fully opened.
The POD clamshell subjects the observer and equipment to more of the wind and elements. The half dome offers fairly good light wind protection compared to a roll off roof but to do imaging or viewing with any wind protection at all pretty much means using the sky 180 degrees "down wind". While I was with Chris when we were using the POD we didn't encounter anything but light winds, but at one point we were talking in the POD and a cold light breeze sprung up and he turned the dome to block the wind. We didn't do any viewing into the wind with the POD so I'll defer to Chris for further input on windy conditions.
Chris's "draftees" that helped him assemble the POD. Note the stars in the dome to strengthen it. At one point I know that they were considering a maple leaf pattern to denote the product's heritage. Also note the "T" handle on the door. It turns a mechanism behind the door that slides bars securely above and below the door.
Chris: POD; I've yet to have the need to turn on my anti-dew heaters, and so far I have had zero dew inside the POD during use or after closed up and checked early in the morning. This fall and next spring will be the true test though.
ED; no dew issues during use, although on a very humid night of viewing, the next morning the inside of the ED was dripping condensation as was my scope. I didn't check the inside for dew before closing up so I can't say if it was there before. This followed a week of 2+" of rain, the ED was sitting on the ground and the carpeted floor was damp. I opened the door and shutter and everything dried out quickly. I didn't have the issue with the POD which was in use a little longer. To be fair the POD sits on wood deck, but I also believe that the dual wall construction of the POD has some effect on this as well.
Jim: This one is hard to quantify without a really dewy night when the two domes were together. I would think that the ED offers better protection because the ED shutter system can be closed up as appropriate. If my target is low on the horizon, I just instinctively close the shutter overhead. I still run a dew shield and dew heaters on my 10" SCT but don't think it is necessary. I have never noticed anything "dewy" inside either ED but I have detected moisture on the inside of the plastic dome as it cools during the night.
With my home ED I have had nights where I have emerged from a dry observatory to a deck wet with dew. I think the ED being a little bit more enclosed has a tendency to forestall dew by retaining some of the body and equipment heat inside.
I can't really offer much on the POD other than the obvious, that it is more exposed and may be more prone to dew than the ED. I'm sure that just having a person and equipment generating heat near the scope will forestall the formation to some extent. Beyond that I have to defer to Chris's judgment.
Ground light protection
Chris: POD; I live in suburbia so I have plenty to block, I move the dome to block the brightest when viewing so the worst is blocked unless I'm viewing in that direction. ED offers much better protection.
Jim: The ExploraDome offers a clear advantage blocking stray ground light. The dome blocks light in every direction except where the observer wishes to view. With the black liner dome liner no light gets through the dome. Occasionally ground bright lights can enter the shutter at an angle and land on the inside of the dome. The black dome liner absorbs and minimizes this stray light. The rest of the round building kit is fairly light tight. The walls of the building are corrugated metal and transmit no light. The upper and lower building rings are plastic and light transmission depends on their color. On the portable the upper ring is black and transmits no light but the lower ring is white and is translucent in sunlight. The shutter door on my portable does not have the black liner applied. In direct sunlight it glows. Since the shutter is normally open for viewing this is not an issue but definitely underscores the desire to get the black liner when ordering the white dome.
The POD was much more translucent in direct sunlight than I expected especially in the bays. Fortunately there is not much in the way of direct ground lights in Chris's back hard and I couldn't tell if direct lighting would cause a 'glow' inside the POD. For as nice as the open clamshell design is at seeing 180 degrees of the stars, it also lets in ambient light. If there is a direct light source within 180 degrees of the clamshell opening the ambient light is going to be an issue. Ambient light would only be an issue with POD if there are ground lights present to contend with. In a dark site environment it would be a mute point for both products.
We ran a quick test to try and qualify the amount of light that can enter the products. We used an SQM (Sky Quality Meter) which measures "brightness", the higher the number the darker the sky. For those of you familiar with the product, the POD rated an 8 and the ED with the un-blackened shutter facing the sun the ED rated a 10.
The ExploraDome set up at a star party and Chris makes a glow POD
Chris: POD; better then my movable panels because I can use the back half of the dome to block the worst of the skyglow.
ED; when we closed the lower an upper shutters so the opening was just enough for the scope, we became completely dark adapted in back yard. I saw some of the best DSO views ever from my backyard. The down side is you lose your orientation with the dome all buttoned up, and lose track of what direction you're facing
Jim: ExploraDome is great to be able to dark adapt in. Like my comment above this is dependent on how much exterior lighting is around the observatory or how bad the skyglow is. If the observer has a truly dark site available to them there probably would not be much of a difference between POD or the ExploraDome.
The above photo is courtesy of a friend's wife at home in the green ED. She wanted to take a picture of the inside of the ExploraDome. I was fully dark adapted and viewing Jupiter, (note the shutter being buttoned up to just the size of the OTA) when she poked her head and the door and snapped this photo. I swear my eyes screamed. I think I was blind for about an hour afterwards.
Door size/ease of entry for observer or equipment
Chris: POD; lower wider door then the ED but entry can be tricky so it's best to do the side step shuffle. Stand sideways next to the door, bend over and step sideways through the door way and stand. Because of its wider door way, it's easier to man handle the scope through by yourself.
ED; the door opening is taller but narrower making it easier to walk straight in. Although I still found it easier and less damaging to your back (if standing too soon after stepping through), if you do the side step shuffle as well, you just don't need to bend over as far. More trouble man handling your scope yourself through the door compared to the POD.
Jim: The POD's door is wider but lower due to its lower wall height, while the ED's door is taller but narrower. Both are not difficult to enter but do require to some dexterity to step, bend, swoop and stand.
As far as loading equipment the POD would be easier because of the ability to hand things over the lower wall through the clamshell. The only way to get equipment into the ED is through the door. At first I had difficulty with this and built a long 'dolly' so I could put it over the door transom, set the OTA on one end and roll it in. Once I got comfortable with going in and out through the door I finally just set the OTA on the transom, step in and lift it. The POD's clamshell definitely makes equipment egress easier by eliminating stooping. If the scope is a permanent mount then it is not much of an issue.
The ExploraDome on left. Note the plywood door and metal corrugated sides. (A "real" foam core door is now offered for the round building). The ED is higher but narrower than the POD. The transom is also higher and wider than the POD. The metal walls are light proof but the lower ring on the ED is white and allows sunlight to penetrate. The upper ring is colored black and blocks all light. The Styrofoam insulation is also visible on the back wall. The POD is on the left. Note the weather stripping around the door seal. The translucency of the plastic can be seen around the base of the wall. The transom height is narrower and lower than the ExploraDome.
Internal storage capability
Chris: If I had the standard POD, interior space is nearly the same with the ED being 4" wider and 13" taller. My POD is a XL-3 and I almost wished I had gotten the XL-5, you can never have enough storage space J With mine, I have a storage bin with drawers in bay. The second with pull out self is the power bay were all electrical, computer and UPS with monitor, keyboard, mouse and ipod player reside on the self. The third bay also has a pull out self were I keep with my EP and BV cases residing on the shelf.
Jim: Due to space limitations my two ExploraDomes are of the round building type without stepouts. I have never seen one but suspect they are similar to POD bays. What I did that works out fairly well to handle equipment was to purchase a small, light mesh-metal file cabinet on wheels from one of the local office supply stores. It fits my lens box or autoguider and I store my books and telescope drop cloth in the drawers. If I had the space I would certainly prefer some form of equipment bays.
Chris's POD is a permanent structure and the bays are definitely a welcome addition.
Currently the folks at ExploraDome are prototyping "stepouts" to replace or be installed in one of the walls. The dimensions are 36'X40" by 24". If you are looking at either product, especially if you have the space and can afford them the more bays or stepouts the better.
Obtaining replacement parts
Chris: The only parts I could see wearing out are the different types of weather stripping which are available from any hardware, lumber stores. All other parts that may get damaged or need to be replaced can be bought from SkyShed.
Jim: Aside from the dome and rings, most replacement parts (or something similar) can be purchased at a local hardware store or building supply company. If you need product specific replacement parts, the vendor is based in Litchfield, Minnesota and have their own shipping trucks for domestic shipping.
With POD being based in Ontario shipping is fairly expensive to the United States. One of the reasons I went with ExploraDome was that the shipping was $125 dollars vs. over $500 for a straight POD. Because of the shipping costs a buyer planning on a POD should probably buy what they want for their final configuration from the start rather than planning "upgrades" over time.
Chris: With the POD, anything is possible I guess with necessity being the mother of invention. For most applications I just don't see the need for it. With its wide opening, there almost no need to have motorized dome rotation unless you're visual and you're jumping from one part of the sky to next. But then you're out there anyway and can manually move the dome. Jim's portable ED with motor drive is cool and it's nice for show and tell, but it's not automated so you're still holding a switch to move the dome. I found it to be quicker and easier just move the dome by hand.
Jim: Currently neither product has automation capability but I'm sure people are working on it. I know that several individuals are actively working on it for the ExploraDome.
My portable ED has an AC dome rotation motor (or the dome can be turned manually as well). There are now shutter cords to open and close the main shutter. I don't think it would be too difficult to automate these features. Probably the difficult issue would be to reliably open and close the lower shutter door.
In time I wouldn't doubt that both products will have some form of automation.
Interior day temperature
Chris: POD; the SkyShedPOD yahoo site is quite active on this subject with many people new to observatories/outside storage of their scopes. I have been using a vinyl garden shed for the past three years so I kind of knew what to expect. From all of the postings I gather that color has little effect on inside temperature because of Infra Red heat gain, lighter color reflect more sun light but stop less IR and dark colors being the opposite. My Lunar(light) grey POD with a single solar vent in the top of the dome and a solar powered attic fan blowing air into my POD through a furnace filter and a small fan on the floor circulating the air, the inside temps on a sunny day are from 10¡F to 18¡F above ambient. Some had reported that their scopes would get warmer than the inside air and when covered with a Reflectix cover (dual foil faced with bubble wrap center sandwich) kept them cool. So using that logic and the fact that Jim's ED with the black liner was cooler, I theorized that it was blocking the IR, the next step was to try and block the IR coming into my POD. I started with the bays which are single walled and when I held my hand near them seemed the warmest. I covered the bays, which face NW, N & NE, with Reflectix and noticed a decrease inside air temperatures of 5¡F. Others on the yahoo site stared to use Reflectix on their domes so I tried that next. I covered the inside of the primary dome (the one that doesn't open) which faces S & SW with Reflectix and now my inside temperature isn't more then 6¡F above ambient.
The white ED dome with black liner and un-lined shutter facing North stayed below +4¡F above ambient. When I rotated the dome so the unlined shutter faced south, the inside temperature increased by a few degrees. This added to my theory that the black liner in the ED blocks IR.
Jim: From Experience I can say ED exterior color has A LOT to do with interior temperature. My permanent ExploraDome is "forest green" to blend in with the golf course surroundings. The portable is white with the layered black interior. The green observatory typically runs 12 to 17 degrees above ambient. On the hottest days I pull the OTA if it is in there. The white ExploraDome on the other hand is better insulated around the walls and I was pleasantly surprised when the 100+ degree heat of Nebraska pushed the interior temperature up only a few degrees. During the week the two domes were together and Chris monitored their interior temperatures and humidity. We also had large amounts of rain during that time. I will let Chris explain what he found about the two domes.
IR heating of the interior seems to be the biggest problem with the POD. Early on in the "beta testing" phase I remember a post by one of the testers that said the interior temperature was 72 degrees when the outside air temperature was 40. I thought this was rather extreme but heard little solid information after that. As the production PODs were deployed it became evident that IR heating of the interior was a significant problem. The POD is fairly translucent and IR heating does not depend on color like with the ExploraDome. At the time of this writing several workarounds were being proposed including a "shower cap" arrangement to cover the dome and block IR or lining the bays with Reflectix insulation. A solution will be found and I think it is only a teething issue. Chris follows this more closely than I do so I will defer further to what he has to say on the issue.
Solar vent in the roof. Solar powered attic fan on a POD bay.
Interior "cool down" and thermal currents
Chris: My POD rapidly cools down as soon as I open the dome and I've noticed zero thermal currents from the POD. On the days that I used the ED, I had left the shutter and door opened during the day to dry it out, (see my comments dew protection) so I didn't have a cool down issue
Jim: Both domes seem to cool down fairly quickly. Since I have not had the ExploraDome though a winter it is hard to say if there is going to be a "chimney effect" or heat escaping though the shutter opening and causing any kind of viewing issues. I know this is talked about in internet posts but as of yet I haven't noticed anything.
POD should have the advantage in being able to "dump out" heat a little faster by opening the clamshell, but the ExploraDome shutter is fairly wide and opens beyond the zenith so it does a good job of allowing heat to escape as well.
Severe weather resistance
Chris: POD; other then the pivot joint (where the two domes pivot on each other) and the top of the door, the rain resistance is excellent. The pivot joint will leak with anything over a light rain, it isn't much but you get some drops on the floor below, the heavier the rain the more you get. The problem is were the joint goes from vertical to horizontal, the rain runs down the dome and hits the weather stripping. The main issue seems to be once the foam weather stripping becomes saturated with water, water passes through it. Skyshed has been working on the issue as well as some users, they have promised to ship out the fix for free once they are done testing the different fixes. They have made a change to new ones shipping now which takes care of this. The other leak I had only happed once when we were hit with quite the storm with the high blowing on the door, I got a small amount of water on the floor by the door which uses the same foam weather stripping and I assumed became saturated and let some water through. Nothing else got wet inside or any other leaks. As to other weather extremes, I noticed no issues with needed to adjust anything for temperature changes, I haven't gone through a winter yet, but if my cheap vinyl shed hasn't had any problems, I don't anticipate any with the POD.
ED; During the week and half that I had Jim's ED here, which includes some pretty good thunder storms, the only leaks I noticed was at the floor. The ED was sitting directly on the ground and a heavy rain could easily have put enough water on the ground to have gotten above the floor in the ED. But no leaks at the shutter or dome ring.
Jim: One criteria area we have not covered is extreme cold weather where plastic contracts. In the case of ExploraDome the wheels are slotted adjustable. Since I have not had the ExploraDome through one winter yet I do not know how much or how often the wheels will need to be adjusted, but I assume some adjustment will be necessary with both products.
I have noticed that on cooler nights the home ExploraDome becomes more difficult to turn. I'm sure that this is because the plastic becomes stiffer and less 'pliable'.
In terms of biblical rains, we had that during our week of testing. The ED remained dry except for the floor. On the portable I had not sealed the floor to the ring and water leaked in that way. My home ED did as well because I used cheap calk that contracted in the sun. I have since used good calk on both units and they remain dry.
With the one piece dome, the only potential leak area would be around the shutter but the top part overlaps the lower part and appears to have enough height and overlap on the dome itself that I have never encountered direct leaks in the dome from rain. About the only entry point I can see would be for light snow flurries or mist to blow in the air gaps between the dome and wall ring but have never noticed this as well.
As far as the POD goes, Chris can explain his product better than I can in terms of leaks. The seams of the POD use some type of high density weather stripping similar to stuff I have used on our sailboat hatch. It lasts for about four years. I know that Chris has permanently sealed his dome halves together since he has no plans to take the POD on the road. The POD does have a leak near the clamshell hinge point and at the time of this writing the manufacturer was trying to come up with a fix. In any event I have seen the leak area and would not be concerned with it. I think proper monitoring and replacement of the weather stripping is essential but if it is maintained and monitored, leaks should not be a major issue.
There was a post questioning snow loads. I don't think this would be an issue with either product because of the curvature of their domes; I don't think either would 'hold' snow.
ExploraDome at the Northwoods Starfest (center between the two domes of the Hobbs Observatory). Once again it was rain tested. Note all the scopes covered but being rained on. With a dome you just close up and lock the door.
Chris: Well this purely subjective, my total cost for the POD/with shipping including all the little extras I've added and the deck was about what I paid for my CPC800XLT. Since I've had the POD, I've used the CPC more then the previous two years combined. Only those who have an observatory can truly know how much more enjoyable it is, the amount of both quantity and quality of time is increased. The ability to go out and be operational in less then three minutes is truly nice, but almost more importantly, after a long night being able to shut down and being back in the house in under five minutes is almost priceless.
Jim: Both products basic units are about equivalent, a straight POD is about $1500 and the round building Exploradome is around $1900. Shipping is a big factor and much more expensive for the Canadian product making the final costs for the basic units comparable. To have the straight POD shipped to my door was over $500 dollars where the ED was $125. If you're planning on a POD, it's probably best to get your final configuration shipped at one time. Beyond the base unit, the POD can be equipped with up to 5 equipment bays.
The ExploraDome can be purchased as a "dome only" product (to be installed on an owner built building) for around $900 including all the necessary kits. Beyond that the Polydome folks are always coming up with new and innovative offerings like the round building kit, stepouts and now a 10'X10' building kit. It is best to visit their website to see what innovations they have.
Chris: The only way you're getting in the POD when it's locked is by making a lot of noise. You need a saw to get though the walls or bays or a big sledge to smash the locking T-handle. I have an alarm sensor in my shed but I don't think I'll be needing one in the POD.
Jim: The ExploraDome has sides made out of metal and a half inch plywood door with a regular house lock and key. The shutter does not come with any kind of lock but installing a simple chain that hooks from the upper ring to the shutter handle would be fairly easy to install. I feel pretty comfortable locking up the equipment at night at the house or a star party. If a user is planning an ExploraDome at a remote or unsecure site, keep in mind it would be fairly easy with a screwdriver or lock to remove one of the wall panels.
The same looks to be true of POD. It secures well with pins holding the shutter down and a regular keyed door lock and vertical bars that lock in the base and top.
Both products are fairly secure but neither would be bullet proof to a determined thief.
Chris. My insurance agent, like Jim's calls it personal property and anything as well and is covered.
Jim: I did some checking on this with my insurance company and found out that insurance is a non-issue. The dome itself is covered as 'personal property' and anything stolen from within would be 'property theft'. Of course I'd recommend checking with your own insurance agent, but ours (State Farm) indicates that insurability of the dome or its contents are no big deal.
Chris: My POD is bolted to a deck which is anchored to the ground, if it blows away, I'll have bigger issues then my Astronomy gear being gone. That being said by their very nature both the POD & ED are domed round structures, so wind just goes around them, I noticed very little if any structure movement while sitting inside the POD during heavy winds.
Jim: The ExploraDome has multiple anchor points around the lower ring for a permanent installation. On the portable I have replaced a couple of the floor anchor bolts with eyes and use ratchet straps to screw in aircraft tiedown coils that sink about 15 inches into the ground. Obviously I only use these if strong weather is suspected or the ED will be set up for a long period of time.
On the home ED I used bolts directly into the decking plus the sealer between the deck and lower ring.
The anchor points for the ED are concaved and water collects in them. Since the upper and lower rings are not solid plastic it is a point for water to intrude into the lower ring. For this reason I used sealant around the shoulders of the bolts before driving them home.
The round building kit weighs about 350 lbs so it would not be real prone to blowing around but there are ways to anchor it permanently or temporarily.
Chris can talk about what POD does, but it is fairly similar.
Ease of assembly
POD and ExploraDome under construction.
Chris: The POD came with an instructional DVD, but the assembly is pretty simple and it took me and a couple of helpers four hours to assemble, and that included watching the DVD. There are a lot of things that take time but it is only done once when it's first put together. I have not tried it, but I can't see it taking more then a half an hour to dissemble for transportation and maybe a little longer to reassemble. There are two bolt holes per wall/bay panel for anchoring it to the ground and using some 12" lag screws to anchor to the ground should be plenty when out in the field.
Jim: I found the assembly of the Exploradome round building kit pretty straight forward. It consists of the fully assembled dome, the upper and lower 8 foot ring, a wheel kit (inline skate wheels, 8 vertical and 8 horizontal, both adjustable), siding panels (regular corrugated metal), door (the first door kits were plywood but they are offering "real" doors now), wheel channels and retaining ring sections.
Basically the door is installed between the rings and the siding placed on with screws into the plastic. The wheels are placed on the upper ring. The wheel channels go into the interior edge of the dome and the dome is lifted into place (It weighs around 180 lbs and was easily lifted by two friends and myself), then retaining sections are installed under the dome.
The dome rings or dome may be out of round after shipment. Given how large the piece are and how they are transported this is understandable. The vendor recommends propping them with 2X4's and "overstretching" them so that they attain their original molded round shape.
This is the major drawback with the ExploraDome. Assembly with the rings out of round will cause the wheels to float back and forth in the wheel channels on the dome. There is about an inch of play in the wheel channel, but if the channel or wheels are more than an inch out of round the horizontal guide wheels will drag and the dome will 'flex' while it rotates. The colder it gets, the more difficult the dome flexes and the harder the dome is to turn.
Getting the dome and rings 'round' before assembly is critical to good dome rotation. All the wheels can be adjusted in or out, but if the channels are out of round more that the inch or so of wiggle room, the dome is going to bind or flex.
The dome I picked up in Litchfield rotates much easier than my dome at home which was shipped. How round the rings and dome are when they arrive (therefore how much correction is required to bring them back into round) is directly dependent on how careful the semi truck driver is. My home dome was loaded on the truck first to be taken off last but the driver switched the route necessitating mine being removed from the truck and reloaded. By the shape the dome arrived in (scuff marks and semi truck floor filth ground into the dome skirt which was puckered in) it was pretty evident that he couldn't tell the difference between a calf shelter and an observatory.
The rings must have been stood up on end in the truck and were out of round. I did the 2X4 thing but apparently didn't "overstretch" the rings enough because the home dome rotates harder.
If an ED buyer is aware of how critical it is to get and assemble their dome with round rings and dome, they will have much less rotation problems as shown by my white portable.
In any event, after a few weeks both the dome and rings will seek their natural round shape. The initial 'teething troubles' I had with the home dome have largely diminished primarily because of the dome and rings 'centering' on their own.
Although I didn't assemble the POD I can extrapolate that the assembly differences would be like building a plastic model for POD ("place pin A in slot B") where ExploraDome is more 'do it yourself' ("drill a hole about 1ž2 inch from the edge for the retaining ring").
Both assemble with a basic knowledge of simple hand tools but there is probably a little more "customizing and trimming" with ExploraDome.
I'm guessing both probably take a couple days to assemble the first time. Both vendors say "in a matter of hours you can be observing". Well, when I built the ExploraDome I was in no rush. I waited 30 years for an observatory I figured I could take my time. With ED it probably takes a week or two to for the dome to settle and to tweak the wheels for the best rotation. During that time you're adding flooring, possibly electrical and lighting so plan on a couple of weeks worth of 'futzing' with either product.
Assembly instruction clarity
Chris: Very concise and easy to follow, and broken up in sections so you easily 'monkey-see, monkey-do' no offense to monkeys intended.
Jim: This is somewhere that I'm sure POD has the upper hand. I have not seen the instructional DVD's for the product but for the ExploraDome the assembly instructions are in page form with color photos and appear printed off an inkjet printer. The instructions and photos at some points were confusing but the assembly is pretty simple and after a few minutes can be sorted out. Not that it really matters, I did notice several typos in the written documentation.
Product fit and finish
Jim: This is another area where I think the POD wins although not by as much a margin as I assumed. The ExploraDome is designed by a company that makes farm equipment. It is completely functional and practical; not much time was put into design aesthetics. It looks like a dome and works like a dome. The door on the round building is a piece of barn yard plywood. For me this is not an issue, plywood is fine. To some sensitive to aesthetics, plywood doors and corrugated metal may not be the look they want.
One of the things I like about the Polydome products is that they are continually adding refinements. A regular door is now offered in place of the plywood door so I can 'upgrade' things like that. Additionally since the basic structures are made out of common building materials they are not only easy to replace, but easy to upgrade if the buyer want to do it themselves. One of the advantages with buying an ExploraDome is that the dome is functional and everything else is replaceable. If we every buy the proverbial cottage on a lake with dark skies someplace where I can put in a permanent building type observatory I have the option to "jack up the dome and throw away the round building" and replace it with a real observatory. With the completely plastic POD I'd be limited to "What you see is what you get". Outside of adding up to 5 bays there currently are no other options.
POD on the other hand does look "space aged", resembling some kind of moon base in the movies. Glow PODs have to be a real trip as well. The POD is solidly constructed but I did notice some molding imperfections and places where seams were not "razor sharp" but more like you'd expect from large pieces of playground furniture. (This last comment is not intended as a detraction from POD's look and fit. (It's the kind of thing where from the posts I was expecting an "A+" and ended up with an "A". The overall quality is still very good for $2000 dollars).
The ExploraDome on the other hand I was expecting imperfections in the plastic and got what I expected. With the dome that was delivered to my home I expected a "C" and ended up with a "D", due to the scratches and gouges from rough handling. The dome I picked up in Litchfield was definitely in the "A" range so I know it is possible to produce. Whether my "D" rated home dome is "par for the course" or a single aberration from shipping I don't know. I assume a lot depends on the driver and how well they load and transport the product.
In both cases one has to remember that they are paying 'only' around $2000 for the functionality of a product that normally costs in the $8000 or $10,000 range. For me, the imperfections in the plastic and aesthetics are well worth saving $6000 dollars.
Chris: No offense Jim, but I think the POD has a more finished look to it, it has an integrated look to it with a smoother finish and texture. All most to the person, the dozen visitors that stopped from my club (NPMAS) seemed to be drawn to the POD.
Product packaging and shipping
Chris: My POD showed up in four large boxes banded and shrink wrapped on top of two pallets. The boxes were beat up upon arrival but there was no damage to any of the part. All needed parts, screws, self pieces, weather stripping and other assorted bits were there. The only issue I had is I had changed the color of the dome to white a couple of weeks after I ordered it. The dome came as I originally ordered it Lunar grey. I called Wayne Parker (owner of Skyshed) and he told me to go a head and put the grey dome on and he would send out a white one to replace it. After the POD was all assembled I was looking at it, the color matched my house, it blending well with the neighborhood. So I called Wayne and told him not to send the white dome, besides SWMBO, liked the grey dome better.
Jim: This is an area (at least in the case of my first ExploraDome) where they need to do some improvement. The domes are shipped on company trucks and the domes are usually stacked like plastic cups on top of one another. Due to the size of the largest components (rings and dome) they cannot be protected in boxes. The smaller things like the door, wall panels and wheel assemblies are boxed. Apparently the condition of the dome at arrival is dependent on the company driver. The first dome was considerably scuffed up. In some areas it looked like it had been grinding on the floor of the semi for a while and had "floor grit" ground into it.
The second Exploradome was picked up directly from the manufacturer and was in much better shape. I personally am not too fussy with things like this preferring functionality to aesthetics but if you are concerned with possible s****es and scuffs on the dome I would recommend that you inform the vendor at the time of order.
From some posts I have read I believe they are now wrapping at the dome skirt (which takes the heaviest pounding) with some kind of plastic wrap. That would alleviate a lot of the problems.
Manual dome rotation
Chris: Jim's portable ED and the POD very close in effort to move with a slight edge in smoothness going to the ED and a slight edge going to the POD for hand holds(something to grab or push to move the dome).
Jim: The ExploraDomes can develop 'sticky spots' from time to time and at different locations. Neither dome has been very difficult to turn and in most cases turns by pushing on a gusset or shutter opening from the inside. Rotation is even easier if done from the outside. I'm guessing that the issues are directly related to the roundness of the domes. Heating or cooling of the dome changes the flexibility of the plastic as well as expand or contract the domes to some extent. If a dome is out of round, it will be easier to turn during warm weather than cool weather. If the dome roundness is good, then the only issue would be contraction of the dome in cool weather and the wheels are adjustable. With both ExploraDomes, the rotation seems to "improve with age".
A couple other issues that affect the rotation is the placement of the retaining ring. If placed too high can cause drag on the wheel carriage bolts at the bottom of the ring. Also if the siding on the round building is too high the lower side of the retaining ring can rub on the top of the corrugated metal siding. Both of these are easy fixes once discovered.
Manual shutter/clamshell operation
Chris: The dome operation on the POD is easy and moves very smoothly. I have seen no posts at the POD yahoo site from anyone who has had an issue with the operation or movement of the dome. The shutter on the ED is a little more complicated and not as smooth with a sticky point at the balance point, but nothing that made it hard or difficult for me to use.
Jim: The shutter on the ExploraDome can sometimes be difficult to operate. On the original domes, operation depended on using a broom handle to push on a hand grip to open the dome and a hook on the end of the broom handle to pull it closed. My green ED works in this fashion. Opening is not too much of a problem. The shutter slides well. Closing the shutter with the broom handle is more difficult because the shutter is fighting gravity as well as needing to be pulled up and forward. With the round building the simplest solution is to go outside the building and easily push it from the bottom "past the hump" of the top of the dome and then it closes easily the rest of the way from the inside.
The White ED has a shutter cord. There is consists of a pulley and cord. The cord goes around the pulley to the back of the shutter and hangs into the observatory. Pulling down on the cord transfers the force to the back of the shutter easily pulling it closed. I believe they now have a shutter opening cord as well that would work fairly similar.
From time to time I also lightly lubricate the slide area with dry Teflon spay.
This is a detail photo of the lower shutter door on the ExploraDome. The lower door is manually operated by pushing open or pulling closed. Under the front of the shutter is Chris's solar attic fan mounted on one of the POD bays.
Chris: While I'm not claustrophobic, I do enjoy being out in the stars. Before deciding on the POD, I had used a roll-off and domed observatory. The POD is a nice blend of those two types, more sky then the dome and more weather/light protection then the roll-off. I was on the preorder list for ED and would have been one of the first people to get one, I had gotten the call and mine would have been on the first truck out. But I had seen the POD and knew that exactly what I was looking for, cancelled the ED and joined the wait list for the POD.
Jim: This is a "personal thing" and something that I don't regularly experience, but it is something that we included because it may be a consideration for some. I do have to admit that with the lack of outside references I sometimes find I lose my bearings when walking or working around the observatory. From an observing standpoint this is not a major issue with a "GOTO" telescope. Often I punch in a target, wait for the telescope to slew and then rotate the dome.
Observer exposure to the elements
Chris: No doubt about it, the ED provides more protection then the POD, and if it wasn't for the POD I would have an ED. But I do enjoy just sitting there and looking out at the sky.
Jim: The POD clamshell is pretty well open where the ExploraDome can be buttoned down pretty tight. In the coming Wisconsin winter where a light sub-zero breeze can freeze exposed skin in minutes, I think the ExploraDome will have a distinct advantage in cold weather.
In really warm weather and doing visual observations the POD would have an advantage. At the Nebraska Star Party the temperature was in the 100's. At night it could be windy. One night it was so windy that most folks weren't even doing any observing but I was able to image from the ExploraDome. The tradeoff was that it was fairly warm in the 'calm air' inside the ED. When I switched to visual later in the night I opened the door to let whatever cross breeze through.
So depending on the outside conditions one dome type could be preferable to the other. The best conclusion would be to buy both.
Interior room and movement
Chris: About equal overall, in order to see zenith in the POD, you need to offset the scope from the center. In my case I move my scope about 8" south of center, now I have more room on the north end viewing south of the scope and less room on the South end viewing north. The ED's shutter opens past zenith so placing the scope in center works best. The ED's higher walls, while providing more light protection requires extending the tripods legs all the way up in order to see close to horizon, were as in the POD, I have the legs collapsed all the way and still see the horizon. The best solution for either is a pier to the most room inside. I would say that two people is about it in either the Ed or POD depending on the size of your scope or type of mount.
Jim: Both POD and the ExploraDome "round building kit" are really "personal' observatories and are not intended to fit a large number of people with any comfort. Both are comparable in size and interior space for general movement. About two people are the max for both products. If a person has a straight POD or round building ExploraDome as I do, dealing with lens boxes or autoguiders also becomes an issue. A small, light table or file cabinet makes life a lot easier if you are moving around the pier and need to move the gear as well.
Using bays or stepouts to get the gear out of the way while you are moving around is of course a huge plus. The tradeoff may be portability of the observatory. If the intended use of the observatory is a permanent installation then bays or stepouts are a must if there is sufficient footprint room at the setup site for them.
The interior dimensions are pretty close between the two. The ExploraDome offers a few extra inches in diameter and about an extra foot of headroom due to the higher walls. This puts the curvature of the dome a little higher as well.
From a mobility standpoint both are fairly close but the additional wall and dome height of the ED would make it easier to accommodate a larger or longer OTA.
The ED interior is on the top and the POD is on the bottom. The ED has a "dropped floor" so that observing equipment can be isolated from the ED floor. Chris's POD is built on a low deck in the yard and has an isolated square section for the tripod.
Chris: POD; has an 8" overhang at the very top so a scope in the center has a blind spot if you look straight up. So if you need to view or image at zenith you need to offset your scope in one direction or a combination of directions, for example SE, to view zenith objects in the south or east skies. This is not an issue if you have GEM mount because when viewing zenith, the scope is offset from the center already. Most users seem to be favoring offsetting the alt/az mounts to the south and some who have them on the wedge move them all the way to the south wall, because they say, your always on the north end of the mount anyway. The ED doesn't have any of these issues although I don't have a wedge so I don't know if that would be an issue with the scope centered.
Jim: Pier placement is much more important than I originally thought. Much depends on the telescope type and mount being used. As an example, with my 10" wedge mounted SCT I have to move the pier 4-5 inches south to keep the fork pivot point in the center of a dome because of the forks "leaning north". If the dome opening directly bisected the zenith, I would need an additional 5 inches to clear the rest of the OTA while pointing at the zenith. Since I run a guidescope on top the whole pier would need to move an additional 3-4 inches south. This is a total of 13 inches. Mounting my equipment in a POD would mean the pier would have to be further offset 8 inches to the south in order to have an unobstructed view or image near the zenith. If I had not known this and placed my pier dead center in the observatory about 23 degrees on any side of the zenith would have been unviewable in a POD due to the blind spot the dome overhang creates. In short I would have had to give up movement room by offsetting my pier to the south or given up part of the sky around of the zenith.
The ExploraDome opens about 8 inches past the zenith. This makes any offsetting, (other than the initial 4-5 inches to put the fork pivot point in the center of the dome) negligible with a 10"SCT.
Different mounts, GEMS, alt/az as well as OTA type and aperture will require different offsets to the pier. It's best to calculate this out with your particular equipment before selecting POD or ExploraDome.
The POD without a pier/tripod offset. The ExploraDome with the shutter open past the zenith but higher walls. Note the black liner, rotation motor and drive ring. To the right of the door is a broom handle that is used to push the shutter open.
Ability as an imaging platform
Chris: I'm not an imager, more of a visual viewer but I believe both would work well in this area, yes the POD has the zenith issue, but there are ways to work around this. I've seen plenty of images from others who used their POD and I believe the longest uninterrupted image was a little over 6.5 hrs, all without moving the dome. The ED with its better light protection and the shutter opening past zenith has the advantage over the POD in that regard, but the dome needs to be moved for long exposures.
Jim: The ExploraDome's conventional design offers excellent wind, dew and light protection for imaging. Before the Exploradome I had to wait for very calm nights to haul all the gear out, set up, align and image. Now I no longer have to contend with this.
As the photo above shows, imaging with fairly windy conditions is possible. When it's windy I can feel air current coming in from the dome/wall joint but not enough to disturb the scope. The ability to batten down the shutter comes in handy for imaging targets even into the wind.
Since Chris doesn't image and we didn't get a chance to use my equipment in the POD I wanted to contact Jim Lafferty who has posted some beautiful images taken from his POD. As Jim's photo shows, a POD can be a capable imaging platform.
There are ways to minimize the zenith blindspot in a POD, either by offsetting the pier, or as the vendor suggests, by removing the dome entirely (like a roll off roof).
How much of an overhead "blind spot" would be equipment dependent. As an example a fork mounted scope with a top mounted guidescope would require a significant pier/tripod offset to image near the zenith. Using equipment like a German Equatorial Mount and off-axis guider would make it less of an issue.
Since Chris does not image, we asked Jim Lafferty if we could use one of his images take from his POD. Jim imaged M16 with an SBIG st2000xm over two nights in near calm conditions (0-5mph). The image is a Ha-SII-Ha-OIII with seventeen 10 minute subs. The scope is a Takahashi TOA130 with reducer on an NJP mount.
This one of M27 is from the green ExploraDome last week. The winds were blowing 16mph gusting 23mph from the southwest so I was making some test images. Even with the winds being up the STV was still able to average around .9-1.2 arc seconds of tracking accuracy. The image is from a Hutech Rebel XT, four subs of 3 minute exposures.
The ExploraDome at the Nebraska Star Party. One of 9 sites it has been to so far.
Chris: Jim's portable ED with its custom trailer is champ here. The standard POD can be broken down and will fit in the back of a pickup or a 5'x8' trailer.
Jim: The realities of taking any observatory on the road are not going to be trivial. These are large (but thankfully light) pieces of equipment. Moving them is akin to transporting a camper or pile of lumber. An adequate vehicle is necessary to either haul or tow the observatories. In the case of the POD it also requires disassembly and reassembly.
To date we have heard of no one in the field actually transporting a POD to a star party, it seems most of the POD installations are permanent (so we have no "assembly time" data but it certainly could be done).
"Have dome will Travel". To date Jim has covered over 2400 miles with the dome in tow.
For the ExploraDome I can say it is a joy to use and take places, (once you get there!). A portable ExploraDome "kit" is not yet offered from the manufacturer but is more of a "do it yourself" project, but can be done rather easily. I provided the tilt trailer and the vendor supplied the necessary hardware. The hardware includes mounting brackets on the trailer, a winch and a "saddle". The saddle supports and carries the entire observatory. It is hinged to the back of the trailer which tilts down to the ground. The saddle is then snugged up to the observatory with cargo straps and a winch tilts the observatory onto the trailer. The trailer is then tiled level. It really is an ingenious setup with no assembly or disassembly of the observatory required. Setup time is an easy 10 minutes; basically tilting the trailer and winching the ExploraDome upright and removing the straps. Loading takes about 30 minutes, primarily installing the cargo straps that go around the dome skirt and base and making sure they are not twisted. Several times I have taken the dome to a dark site for part of an evening and loaded it up in the dark.
Hinged to the back of the tilt trailer is the "saddle" that holds the ExploraDome in transport.
The desire for a portable observatory has to be weighed against the extra cost and issues associated with its transport. In my case I do a fair amount of imaging at remote sites so a portable observatory is a dream come true.
From a portability standpoint I think a portable Exploradome is about as easy as you can get. There is no assembly or disassembly time of the actual building itself. It's mainly taking off or putting on the straps once the building has been winched onto or off of the trailer. The Portable ED makes going to a dark site alone for a night (or even part of a night) with a fully functional observatory a practical reality. Taking a POD on the road would be a possibility but would probably be more difficult and time consuming with the assembly and disassembly. I wouldn't doubt that it would be possible to make a similar trailer rig for a POD as the ED has so it could be transported intact in a similar fashion.
HOA, SHMBO and covenant considerations
Chris: This is area where the POD and portable ED stand above the rest. They can easily be considered temporary structures, this is the reason I don't have a pier and use a heavy duty extension cord for power.
Jim: Where I live there are covenants and like half of America that want to do anything in their backyard I was trying to find ways around them. The best I can offer on this subject is to make sure you check ahead of time. When I was first looking at POD and or the original building ExploraDome I assumed POD, being "plastic like a swing set" would be a non-issue. I found out that anything besides the living quarters (even an attached garage) is considered an "auxiliary structure" and subject to restrictions. To meet the letter of the law I would have to "tear down the observatory after each use" if someone complained.
I was able to work with our village engineer and add the ExploraDome to the deck where it would be classified along the lines of a gazebo or hot tub and therefore "legal".
So the best advice I can give is don't 'assume' anything about how building codes or HOA restrictions will view a plastic building. Go and check ahead of time. In my case the village engineer was very helpful and supportive in helping me find a 'legal' way to attach an observatory to the deck.
One sideline though, be aware that taking any building permits out gets turned over to the wonderful property tax folks. They assessed that the additional 40 square feet deck space increased our home value by $1,300 dollars. You got to love our government.
Dealing with village officials was easy compared to the delicate negotiations with She Who Must Be Obeyed. "It must be invisible and cost nothing". Well green was most 'camouflaged' color I could find.
Chris's wife Jackie is on the left. When I talked to Chris about a possible review of the AstroGazer observatory, Chris told me Jackie said, "Oh no! Not another POD!"
Chris: Both the POD and Explora-Dome meet my requirements, if the POD wasn't available, I would be happy with the ED. Overall I prefer the POD, no surprise here, I mean I am biased, but it fits my needs and viewing styles the best. But this is true for just about everything in Astronomy, find out what works best for you, there are plenty of opinions out there, but that is all they are, opinions. I've used my POD for two months now, about 10 viewing sessions and I used the ED three times, I tried to be as subjective as possible in this comparison, but in the end it's just my opinion. The one thing I know Jim and I can agree on is that an observatory gives you more enjoyable time under the stars and in the end, isn't that what it's all about.
Clear Skies all, Chris
Jim: I think both products are excellent additions for the astronomical community. Both serve their intended function, and both have their strong points and teething issues.
It is important that a potential buyer evaluate the type of equipment they plan to use in the observatory. Both observatories can accommodate small and medium sized apertures very well. The functionality of larger scopes in the 10+ inch range will depend largely on mount type, pier placement and height. As an example the extra dome height of the ExploraDome probably makes it a better candidate for SCT type OTA's in excess of 10 inches. The lower wall height and clamshell design probably makes POD a better choice for a dob.
The potential observatory owner also needs to assess what kind of observing or imaging they are primarily going to do. If your primary intent is "casually viewing" of multiple targets around the sky throughout the night, the clamshell design of POD is probably the right choice. If you are planning more serious endeavors such as research or imaging, the clear zenith, centralized pier location, additional wind, dew and light protection possible with the ExploraDome probably makes that a better candidate.
For closing thoughts I would like to thank Chris for his hospitality in sharing his POD and his yard. If ExploraDome had not come out with the round building kit I most certainly would have had a POD in my back yard. I think both products fill a much needed and welcome niche in amateur astronomy. I hope this review sparks an interest in both
After carrying 200+ pounds of gear outside every time to use it, polar aligning it, image and then have to tear it down and carry it in again, I can only come to one conclusion, and I hope others do too.
A dome is good.
This was the first picture taken of the POD and ED together. Note the grass after a two month drought. Compare this picture to the first one in the article taken at the end of the week. You'll get an idea of how much rain we experienced during the week.
Last minute thoughts and Addendums as this goes to post:
The round building instructions are now more clear and professional. My round building was one of the first production units and instructions were literally printed off an inkjet printer.
Since this review was initially written there have been some updates to both products.
The ExploraDome round building now offers a real foam core door as well as a 10'X10' building kit.
Reports on lining PODs with Reflectix panels to the bay and dome areas appear to have the heat issue under control (about 5 degrees above ambient). There have been some modifications to the weather stripping placement to address the hinge pivot leak.
The Astrogazer arrived a week ago for evaluation. Next month a full review of the product will be posted. Since the AstroGazer is a viable contender in terms of portability and deserves mention in this review.
AstroGazer summary: Basically it is a large (10'X8.5'), vinyl/fabric covered structure with a rotating dome.
Preliminary findings are that the product is very strong, very light and highly portable. The components can be packed in three bags, the longest being 60 inches. It appears to offer excellent wind, dew, light and weather protection. Assembly requires no tools and is under an hour for two people.
This product would be an excellent choice for those that would like dome functionality on a "temporary" basis (star parties etc) but can not commit yard space for a permanent structure like a POD or ED.
The AG would be an excellent choice for those with a large scope that is traveling to a star party that desire dome functionality and element protection in a highly portable package nor requiring a trailer or entire truck bed.
This coming weekend the AG will be battle tested at the Two Hearted Star Party in upper Michigan.
The vendor started shipping the product in February of this year and there are 26 units sold (as of September '07). For further information on this product:
Astrogizmos (AstroGazer) Homepage: