Setting up all your gear and packing it up again at 5am, sleep deprivation, freezing cold – we’re all familiar with these joys of astronomy! I also live in fear of dropping my telescope while mounting it or nodding off only to awaken to a water-drenched nightmare.
I had been fantasizing about owning an observatory for quite a while and had considered options including a roll-off roof and clamshell. Considering cost, effort, and features, I chose the NexDome, and I’ll be sharing my experiences with it here.
Why an observatory?
Always ready: The permanent setup now means my complicated system is ready to go, saving me a lot of time and effort.
Polar alignment: A fixed mount also means I can take the time to get near perfect polar alignment once and never have to move it again. Likewise, not moving my reflector means I can go months (or longer) without the need to collimate.
Temperature acclimatization: Having it in a dome outside means it’s always close to the ambient temperature. There’s no need to wait hours to be sure the equipment has cooled properly.
Why a Dome?
Having a classic white dome is a great feeling, more like operating an observatory rather than a shed, but there are many other reasons for having your setup in a dome.
Light pollution: Being a backyard astrophotographer often means putting up with stray light. A dome, with its directional view of the sky, does a good job of blocking unwanted light (think racehorse blinders).
Wind protection: There is a real feeling of encapsulation inside a dome. When it’s windy, I can barely feel anything inside the dome. This helps with stability and image quality since the autoguider and mount are not constantly battling the wind.
Dew protection: I used a roll-off roof many years ago, but it didn’t help prevent dew. In coastal Vancouver where I live, the relative humidity often exceeds 90% but inside the dome my gear rarely has dew settle on it. Dew heaters are still needed for the telescope, though.
Protection from ground seeing effects: Normally, heat rising from the ground in front of the telescope can cause poor local seeing. With the dome, I use a 10-inch (25cm) fan to pull cooler air in through the shutter right in front of the telescope. Warm air that have might risen from the floor blown out the exhaust vent in the back of the dome.
Domes aren’t without some downsides. They can be a bit more complicated to set up and synchronize with the mount than a roll-off roof. If you’re doing something requiring fast telescope slewing like tracking a satellite, a dome may not rotate fast enough to keep up with the telescope. Space may also be limited at times.
The NexDome Design
NexDome are made of a series of relatively lightweight plastic panels that are UV protected.
They are packed and shipped internationally with the panels nested and assembled on site, at much lower cost than shipping assembled dome.
Walls: The panels have reinforcement webbing that adds stiffness. Seven heavy-gauge square aluminum pillars function as the backbone of the walls and transfer the load of the dome to the foundation. The base of each pillar has a bracket to allow bolting it to a foundation.
Dome: The dome rotates smoothly on 14 ball-bearing rollers except for the little bumps where wall panels meet. This causes the dome to jerk, which bothered me, and I spent 20 minutes filling the gaps with a bit of epoxy resin.
The interior of the dome has adequate space for most amateur-sized telescopes, and there are extra bays for storage of additional equipment as options.
The Planewave CDK 12.5” telescope I have in my NexDome is both longer and wider than a 14” SCT. An even larger CDK 14” telescope will replace it soon. That’s the largest OTA I expect would fit in the NexDome.
Shutter: The shutter has two panels that open well clear of the zenith, allowing imaging directly overhead.
The dome design I have includes rails on both sides of the shutter that allows it to slide on rollers while being held securely, avoiding unwanted motion. On older versions, the panels slid over each other with no rails to guide them.
My version has aluminum rails but the latest design includes Ultra-high-molecular-weight polyethylene (UHMW), which has very low friction and high resistance to wear. The shutter’s width is 24 inches (61cm).
The NexDome can be purchased with its own walls ($3,195), or you can buy the dome and install it on your own structure using a ring that is provided by NexDome ($2,295). Optional bays can be added for extra space ($499 each). The bays replace any one of the wall panels. I have one bay for my laptop but up to six can be added. The modular design makes it very easy to replace a damaged part. The NexDome warranty terms are also very good (three-year limited warranty to the original owner).
Assembly took me about two days, and a helper is needed. While there are instructions available online, they are not very detailed, and you have to figure out some things yourself.
The panels fit together well most of the time, but it did need a bit of elbow grease on occasion, and I redrilled some holes to make assembly easier. A lock is provided, and it works, but it doesn’t provide great security.
The shutter required a bit of tinkering to get it slide as well as I’d like, but the newer ones are supposed to be easier to install. Overall, it took me a few extra days to have it fully operational.
Living in Vancouver, rain is a big concern. I’ve had the NexDome for six months now and it has never leaked. I get a tiny bit of moisture under the walls, but the gap between the walls and the floor could easily be filled with caulk.
If you live in a humid climate, I recommend adding a small dehumidifier to protect your gear when the dome is shut. I use a Toshiba 50 pint auto set to 70% with a hose to dump the collected water outside. I’ve noticed some moss and water on the dome gutters, but they don’t affect the operation of the dome.
The dome is about 95% opaque. A fan helps keep the temperatures down in the summer. If you’re in a dusty area, while the panels are sealed I can’t say if dust might get in through the gap between the dome and walls (they are covered but not sealed).
Automation is essential for imaging, especially dome rotation. NexDome uses the new Lunatico Beaver controller, which is simple, efficient, is ASCOM compliant, and works very well with my imaging software, NINA.
The dome has a rotation motor ($899) and a wireless shutter motor ($1,049) that includes a lithium battery charger. The Dome is wireless to avoid tangled wires as it rotates. The controller is included with the rotation motor.
The Beaver Dome software is straightforward, but you do have to set the dimensional measurements of the dome and mount accurately for it to sync perfectly with your telescope. I use my setup remotely from inside the house without any issues.
There are proximity sensors on the shutter open and shut locations to stop it at those set points. Once closed, the shutter’s battery terminals magnetically connect and charge the wireless shutter motor’s battery with the provided charger.
The dome azimuth position is recalibrated every time it goes past a sensor, so it’s quite accurate. Without this sensor, the dome wouldn’t know its exact orientation.
Rain sensor: This was one of the main reasons I selected the NexDome. The optional rain sensor ($350) is hardwired to the motor and controller. The instant it sees a few drops of rain, it triggers the shutter close command even if there is no computer or software connected to it. I’ve tested the rain sensor several times by spraying a few drops of water on it and it has worked every time. I highly recommend it if you like to sleep during your imaging sessions!
Low battery: The shutter will automatically shut when battery voltage drops below 11 volts. This ensures the dome can’t get stuck in the open position with a dead battery if rain is detected.
Security: You can lock the door, but someone could still break in with moderate effort. I‘ve installed a wireless security camera in the dome with motion notifications (Wzye Cam with night vision).
Internal security camera view. Credit: Rouzbeh Bidshahri
After a few weeks setting up the NexDome and optional gear, I now start my imaging sequence and go to bed. The automated setup finishes imaging, parks the telescope, and closes the shutter. I’m able to function the next day after a good night’s sleep, which makes this already challenging hobby a bit more convenient, especially on cold winter nights.
Overall, after a bit of tinkering, my productivity has gone up with my imaging setup in the NexDome. I can now take advantage of even short windows of clear sky without the need to set everything up and tear it down again. I have to say it has changed my astronomy experience and even increased my wife’s level of approval!
MSRP: $3,195 (without bay or automation accessories)
Editor’s note: AstroGear Today co-owner Babak Sedehi is the owner of NexDome. The reviewer is not associated with NexDome, and the writing and editing of this review were handled entirely by AGT co-owner Mike Simmons to ensure a fair and honest review, with no influence from the manufacturer. Just as with all our reviews.