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Like many of us, I was a little bit peeved at the time it takes to move about 50-100Kg of kit, set it up, make all the electrical connections, polar align, calibrate the GOTO system and fix anything that has gone wrong (it always does) prior to starting out a session - and that's if it's still clear. And then there's the packing it away again at the end of the night. It was such a chore that unless the forecast was clear all night long I tended not to bother. To make my hobby enjoyable again, I needed an observatory. There are a number of options: 1) Roll-off roof 2) Roll-off shed 3) Clamshell 4) Dome These all have their pros and cons. 1 & 2 are cheap, but need additional garden space to roll them off. The way my garden was set up, and the location I wanted the observatory, meant that I discounted them. The only clamshell easily available in the UK is the SkyPod, and whilst I considered it for some time, I finally got put off by the trouble imaging straight up and the reports of leaks. So that left a dome. The problem with a dome is that they are expensive - and for imaging they need automating (even more expensive). Still, that seemed like the best solution for me. In The UK, the dome that is most easily available is the one from Pulsar observatories. It is available in 2.2 and 2.7m sizes and can be made in white or green (possibly other colours too, white and green are the only ones I have seen). I had seen a dome at a fellow astronomers house - and he had successfully motorized it which meant that I could follow his plans. I'm, OK at tinkering with things, and can actually even be good at it, but for expediencies sake I'd rather get something off the shelf and I'd be rather upset if I found that I couldn't motorize it as I wouldn't be able to image which is my only interest in the hobby. So when Pulsar adjusted their design (see later) and made a fully motorised observatory "off the shelf" an option I decided to go for it. I bought a dome, dome controller, shutter controller and a Shelyak Dome Tracker. Pulsar 2.2m Dome Oberservatory Shelyak Dome Tracker I took a while building the base in my garden - there's a separate thread for that. It needs at least a 2.4m circular or square concrete slab. I went the circular route as it's much harder to build. They suggest a 1m square base for the pier, but I decided 75cm would be more than enough. I made a £500 deposit by credit card (for the protection it offers) and then the rest was paid by bank transfer 3 months later when the dome was ready to deliver. Unfortunately they are built in Norwich and I live in Somerset, so there was a hefty delivery charge. They also offer to assemble everything for a small fee and given that I was into this for quite a sum already, I thought I may as well ensure it got set up properly. I bought an Astro Engineering pier from them too. On the appointed day the guys from Pulsar arrived and set about work, fortunately in good weather. They were finished by mid-afternoon and showed me how the observatory worked - as well as installing up the basic Shelyak Dome Tracker software on my PC. Unfortunately we hit a bit of a snag here, as it wouldn't work! I got a second laptop out, and fortunately it did work on that - but when I checked it again a few hours later after they had gone, it didn't work anymore. Time to pull my hair out! To cut a long story short, I had email communication with the guys from Shelyak and Pulsar over the next 24 hours - they identified a problem with a component not working properly at low temperatures (a December install) and they sent me a new unit. They also wrote a new driver, which meant that the faulty component wouldn't cause trouble anymore anyway. Good service. When I finally got permanent electricity installed to my observatory, I set up my kit properly. The dome moves by two motorised wheels (blue) pressing on the side of the dome. These are powered by a 12v 10a transformer. There is another wheel (the grey one) which is attached to a rotary encoder so the dome knows how far it has travelled. The "home" position is set by a metallic sensor - mine is at 290 degrees. You can see it in between the IR sensors below - it's just a bit of tin foil. When the dome is told to home itself, it rotates until it finds the home sensor and then sets its internal position to 290. From there on, it counts clockwise and anticlockwise motion via the rotary encoder. In addition to the computer control, the dome can be set to track at sidereal rate (or various fractions/multiples thereof - remember, the dome isn't equatorially mounted) if you didn't want to use a computer. The Shelyak unit is nicely hidden away behind the dome controller metalwork too. It connects to the computer via RS232, but they throw in a USB-RS232 cable in case you need one. The shutter mechanism is attached to the dome part which makes getting power to it more difficult. The solution that Pulsar have come up with is a 12V battery and a solar panel. To send signals from the Shelyak Dome Tracker, they have utilised an IR connection. The open/close shutter will thus only work when the dome is at the home position, as this is when the IR sensors are aligned. It closes the shutter by means of a chain and sprocket. There is a manual open/close button in addition to the computer control. To get the dome automated you need to enter a few details, such as the size of the observatory, the number of steps for a full revolution, the position of the pier how high the centre of the scope is above the rotation axis of the mount. After that, it's plain sailing - rather than use the normal ASCOM driver for the mount, you use the ASCOM Dome Control driver instead (comes with ASCOM) - which itself connects to the dome and to the mount. You slave the dome to the mount and then when you issue slew commands, it moves both the dome and the mount to the right position and keeps them there throughout the night. And this is it in action:
Since my telescope can hit the roof, I incorporated two safety switches on the RA and DEC axis, these switches are closed when the telescope is in the "telescope safe" position. I've also incorporated a third safety switch on the drop down wall. So for the roof to open or close all three switches must be in the closed positions. My second safety feature are design to minimize the chance of rain from entering the obsey when the roof is open. I've went for a total of three rain sensors, all of which are independent of each another. The main rain sensor is integrated into the cloud sensor and so far this has never failed. However, it is dependent on my obsey PC working correctly. I therefore decided that I needed a back up sensor that would trigger an alarm in my house if it detected rain when the roof when open- so I went for a battery powered wireless weather station approach - whilst this works, on testing it I was concerned that it requires quite a bit of rain before the sensor is triggered. I therefore decided on a more sensitive rain alarm sensor which sits on my warm room roof. This sensor also incorporates a heater, so needs to mains powered, it is interfaced it to a battery powered wireless alarm via a battery powered wireless link to my house. For the time being, I've decided not to install a UPS but I do have a mains power detector alarmed in the house. So, when I'm observing it's normally from a PC screen in the house. I recently decided to purchase CCDNavigator which has recently been upgraded to be ACP Compatible which makes programming an observing session very easy. Overall, I've been impressed by not only the physical build but also of the quality of the controlling software, which has proved very reliable.