skybadger

I too have a quark chromo. It too comes on band very easily but at least it requires some power. I believe it's heat from the sun heating the filter and so it really needs an erf to take a lot of the energy out of the beam before it hits the filter.

I have had two domes now at three locations and stored and operated a computer in each of them., with mains and associated usb/serial cabling As long as the pc stays warm - for me that meant always on - it was fine. If it failed to start after a power cut then it got damp and the harddrive didn;t ike to play ball unles it came inside for a holiday and dry out. The mains has never been a problem, rusting usb connectors have. While i also understand the issues about 5.5 power jacks and lack of industrial latched connectors, once fitted, they don;t move in practice and i don't have a vibration problem so I haven;t seen the need. XLR connectors have been a solution for some. Not cheap. In fact, the biggest issue I have had is the humidity over long periods causes or promotes mould on glassware stored outdoors for long periods, so every few years I have to clean down the surfaces of lenses which can be a bit daunting.. Other than that, until now I haven;t seen the need for humidity control and have seen good reports of solar powered vents to provide venting, but now I have a humidity sensor in the dome and can clearly see that it reaches 80% during the night and down to 20% during the day when it warms up, with clear impacts from opening the dome or the doors. That might drive me to be a bit more active in getting some venting fitted. The sensor data below is from an automotive standard HTU21D temp/humidity sensor suspended in free air inside the top of the dome.

next pic - view from outside. You can see the top shutter edge lined with screws that hold a ptfe wiper blade , which is probably the ultimate cause of this problem. The lower shutter is partially retracted under the upper. The shiny thing is the back of the monitor in the dome.

Hi all Thanks for the replies I normally reply as I get them but it seems my notifications are not coming through. I appreciate the need for a drawing or diagram or photographs so I'll get on to that. Sloz - the dome already exists and can't use a lower shutter that folds out instead of folds up - there is not space during rotation. Old eyes - thats where my son and I were getting to something similar - magnets, torque dampers and rope, sliding frictional track, something to friction bind or toggle the top to the bottom with. Or a gravity activated clamp that catches when the shutters are almost horizontal ( ie on the top of the dome) but releases when getting back to vertical during closure. Next - some pics. Inside of dome - shutter closed. Insides are secured by internal rollers and uses a prong and electric latch to secure. Cord at top of lower shutter is an elastic rope to the end of hte top shutter in attempt to stop slide. It doesnt'. Shutter fully open, lower retracted under upper and both back over the slot. Limit switch to left not yet engaged. Visible are two compasses for dome rotation measurement. . Shutters partially open, lower retracted under top and top about to break free and hit end stops.

good luck running a dome from there. without running all the electrics to it .

Hi i put mine at the south side of the observatory, which is cramped when the scope is homed to the pole and frequently gets knocked, so I need to remember t park up east/west more often. While I take your point about heat, most pcs these days don;t put a lot of heat out and I dont see it as slot seeing during taking video of the moon for example. However, I do think I'd think seriously about putting it on the north side of the dome since there is less use of the scopes from there, even when viewing the meridian. But you would have to think hard about the risk of disturbing them during an imaging run whhen they are most likely to be camera end to the pc/workstation as you image across the meridian. That was what made me put it on the south side originally. Mike

Hi all 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. Ideas: 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. Mike

That sounds like poor permissions management by the app rather than windows itself. Prolific on the other hand are a piece of poo and I was surprised that FLO are selling an adapter based on this chip. Vendors such as FTDI are available for 8£ for the same job. I have a prolific on my EQ8 at the mo and it drops out occasionally which is really annoying.

Because those last ones are centered around the sun, they are more rainbow arcs than iridescent clouds, which have different causes but are no less pretty and infrequent

In driving a telescope you are looking for a high dynamic range, from fine guiding to degrees per second slew. Using steppers you have a top frequency y limited by resonance and a bottom one through diminishing returns in micro stepping. Using DC motors you have a different problem of a top speed limited by DC current and a bottom one managed by positional servoing. So you have to consider what ranges you want your motor to operate over and pick accordingly. Note that the large friction drive mounts have small DC motors which are geared down in the motor but offer a large dynamic range due to their high internal rpm . Consider that, if you want to use a stepper, in the eyepiece you may want 1/16 steps, 8 per second, resulting in a step rate of .5 per second, but each ustep is 2". Most people aim for fractions of " per ustep. Then you also have to drive stepper at >1KHz to get useful slew rates using full steps. So you have to pick your stepper carefully.

I set my 1" square tiles on edge in cement. Haven't had problems rough grinding at all. Created a new cement form for polishing by casting against the mirror then mounting the pitch. Those tiles aren't going to wear out. I like the wax idea, though it runs the risk of picking up grit as well as removing it. M

I've written an ascom relay control that uses the alpaca interface for wireless control. Currently the hardware is on the bench while I complete the same approach for the dome controller. It means you can plug any commercial relay board into the ascom switch model. It'll be doing the same for heater control, in ascom, it's a variable switch.... Mike.

I used a 50 mm filter screwed to the front of the quark , caused the view to lose clarity in my opinion.

Hi intercipere, great work. Can you elaborate on your experience regarding friction vs belts? Is it due to the accuracy of the printed surface ?

Id be surprised at that- the drivers will have current control and chopper circuits managing that. My guess first is high resistance connection - you need 2 amps or so through those drive pins. Can you rig up a load resistor and meter to check for current ? Have you an oscilloscope to look at the motor drive signal ?

I've had no problems with tp-link eop adapters. Wi-Fi was spotty and unreliable over 30m. Eop has been fine. I'm not sure tha they are that noisy anymore. They used to be. ..

Hi Here is the drive I described. The motor sits on the gearbox towards the bottom and drives the central pulley through a pair of 4:1 reductions. The two idlers either side provide tensioning and the timing belt then loops over the two idler pulleys supporting the bottom of the horseshoe and stretches around the curve of the horseshoe between them. That way the drive pulley works on the toothed side and the horseshoe sees the smooth side. Regs Mike

Fair point, I don't get a lot time to maintain it and know my way around. This should work, I viewed it last night. https://www.skybadger.net/equipment/worthing12inchscope.shtml

You can see mine at www.skybadger.net if it helps. Should have said earlier. I need to dig out a photo of the update drive train described above.

I worry about this advice. Friction drives are chosen because it's easy to make 'perfect' circles. The overall accuracy is likely better not worse than a geared wheel. The choice of whether to drive a stepper or a servo is purely about your ability to measure and manage the speed, in your case either will do fine, for geared or friction drives. There is no difference in 'drift' susceptability. Use of a 'pressed'' gear like you describe has been successful but I wouldn't do it into the end grain of a sheet of ply... is that where the strip of oak is envisaged ? There will be much more variation than routed disk on bearing.

Osprey, I use a toothed belt, smooth side facing the horseshoe and toothed side facing the motor sprocket. That way I get a long friction surface rather than a single point. The wheel is supported by two support bearings, over which the belt runs ,so that is where most friction will be experienced. Seems to work nicely by hand... I too recommend onstep, but last time I looked it couldn't handle DC servo motors.

Hi, my name was mentioned ? I used a DC friction drive on my horseshoe, with incremental encoder for speed control. Big drive wheel, eventually use pec, should be nice and smooth. Sadly not quite there yet, have the drive unit and motors but destroyed the mount in a classic wheelbarrow accident. Will be reassembled eventually. I agree withe observation that a refractor is going to be an interesting choice ! Mike

Yep.as shown below.

It's all in the same box, ir sensor next to the Lux meter lens and both talk i2c via the esp.

Took the leds off the power regulator, the esp8266 and the melexis pcb. Now I get log(Lux) at -3.4 compared to -2.5. So a factor of 8 sensitivity improvement due to a reduced background. Or about 2 magnitudes.