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After automating the dome on my Pulsar Obsy which has been a revelation, I have spent a considerable time researching how I could automate on what is a very basic manual shutter. The existing shutter slides on the aperture side of the dome and supported by two curved aluminium rods at the rear. What I will require is to create a runner system to allow the shutter to open & close smoothly, be aligned & contained to enable attaching a motor and drive system, thus allowing software automation.
The rollers are 30 mm dia nylon roller bearings, four per side of the shutter opening. This will allow the shutter to slide smoothly over the open aperture.
The rear side of the dome needed to be built up so I could affix tracks to enable the shutter to slide smoothly to the rear of the dome. This was relatively tricky as I had to build rear track support blocks to line up with the existing shutter. I plumped for wooden supports as I had to mount the on a sloping curved dome and as they had to be mounted vertically, creating some rather complex compound angles and curves. These were bonded in place and further secured with stainless screws from within the dome. Then having formed the arc in which the shutter will run I attached UPVC strips to complete the assembly. The sides will be cladded with UPVC.
The calculations had to be quite precise as I didn't have much breathing space
To be continued...........
I am finally getting to the point of having a working dome and shutter driver from an electronics point of view:
I have alpaca controllers and drivers for both, sensor switches in place for the shutter travel, encoder for the dome rotation, relay latch for unlocking the shutter, motor drivers for the opening motor.
I've also put in place a bicycle-wire based winch system to raise and lower the lower shutter on an endless rope system.
What's missing is this:
When winching, the lower shutter rises on the rails up the slot and under the lower shutter to a certain point and then brings the upper shutter with it by virtue of pressing under the bottom edge.
When the lower shutter raises to a certain point on the cycle, gravity takes over, the top part of the shutter unhooks from the lower part and slides down the back of the dome with a a crash into the buffers.
I'd really rather that didn't happen, since the buffers and the dome they are attached to wont last long doing that regularly.
I tried putting shock cord elastic between the two so the larger upper part couldnt run away but the lengths are wrong and wouldnt allow the shutters to close properly with the right length to prevent or at least dampen runaway.
What I am looking for is ideas to prevent this happening in a reliable way so the dome automation can do its job, night after night.
What I find is writing about the problem also helps me think about it, so hope this is useful.
The winch system:
The bicycle wire system has rollers on the inside of the shutter rail that guide the wire that is pulling the shutter up , which is fastened to the lower edge of the lower shutter. The wire goes up to the top of the dome, round a pulley and then back again, this time inside bicycle wire guide tube which mean I can more or less run it where I like with a small amount of give. In this case it runs back along the rail down to the winch. The wire wraps around the winch about 3 or 4 times and then fastens on the shutter again.
Something to make the upper shutter stick to the driven lower shutter on the way up and come apart on the way down ...
Something to dampen the crashing of the shutter into the buffer...
hope this stirs your creative engineering juices.
I have a steel pier for sale. This was purchased along with a pulsar dome and believe it is an older Pulsar model. The pier sat in a yard, exposed to the elements for a few years before I purchased it so there is some surface rust and flaking paint but will clean up nicely. £250 and buyer will need to collect from Suffolk.
I need to lift off the dome of my 2.2 metre Pulsar observatory so I can smooth out the joints between the 4 sections. They are causing problems when the dome is rotated. When I bought the dome it was installed by Pulsar so I have no experience of lifting the dome on or off the walls. My plan is to use 4 Acrow props to do the lifting so I can do it as a one man operation. I assume that it is best to place the props outside the dome and lift using the edge of the dome. Can I ask anyone with experience of these Pulsar domes if this is the right way and are there any snags?
I and my girlfriend has come home from a one week travel at Malta, a small island in the Medeterranien Sea. About a mount before we go I came in contact with an amateur astronomer down there, Maurice. He invited me and my girfriend to visit him and his DIY built observatory.
The observatory is built on top of his house and it has a real dome.
If you find it interesting to read about it I have done a small report from our visit at the Malta observatory with photos:
The Raven and the Owl observatory, Malta.
After this visit it's hard to understand why we stay in Sweden where we live, when it's dark it's also very cold. We often have from -20 degrees to 0 degrees Celcius temperatures. Now adays we don't have many clear nights either.