are there any cheap methods for motorising a sirius dome?

[h0ughy]

I was given a windscreen wiper motor with a wheel on it when i bought my 2.3m sirius dome though that was never used (i could be wrong on this point. Are there any ways/methods or perhaps a tried and true method for rotating the dome cheaply?

i was thinking of a pulley system - then i thought how would that attach and work. then i thought of a chain? I am mechanically stumped (and challenged)

[allan gould]

are there any cheap methods for motorising a sirius dome?

No

[bert]

If you like diy.
http://www.dppobservatory.net/DomeAutomation/SiriusImplementation.pdf

I have been playing with lesvedome for some time, Pierre is very helpful also.

Brett

[cohiba]

Guys
Somthing else to go wrong, just give it a push like I do the excersie will do you good

[h0ughy]

ok am not against this, but when you need to spend time with the family and your constantly running outside - not good. also like a longer imaging run and get some sleep for morning shots ;)

[allan gould]

David
Ive been thinking along the same lines but to be honest youre in for big bucks again to motorise it.
Ive been thinking of a motor thats actuated with a scope mounted laser.
When the laser/light hits a pad/sensor on the dome slit the motor is switched on briefly.
But it may take more nouse than I have to realise it. JayCar have some interesting motors and kits.
Allan

[Photon Addict]

The following idea is still a seed and may not work, but it may stimulate further ideas from people much smarter than me. Please, comments and suggestions are requested!! I do not take credit for the idea, as it was implemented in some professional observatories in the 80's.

1) Dome azimuth feedback mechanism - Using a CCD Linear Barcode Scanner with a USB interface (an example of which can be seen at www.skycomp.com.au/product.aspx?id=50562) to read the azimuth of the dome slit. Print a few barcodes using the PC and stick them to the dome at the required interval. One can even use "barcode fonts" to print out the labels. From the limited understanding I have, some scanners' output is the same as a PC keyboards' input, so if the scanner reads a barcode that "says in barcode", say 25 degrees, then the software reads "25" as if it was typed in on a keyboard. This simplicity appeals to me. I am sure there will be a way to "read" this input in software and compare this input to the telescopes' azimuth that can be read in ASCOM. A simple difference calculation can then determine an appropriate length of time to energise the wiper motor. The same idea as Allan's, but not using a laser and sensor.

Another aspect that is appealing is that there is no requirement for the motor to be in sync with the dome azimuth feedback mechanism - the barcodes give the absolute azimuth. Therefore, if the motor "slips" while driving the dome, it makes no difference as it will just make another correction after it is finished until it is within some error tolerance. This is assuming the dome is not being continuously driven (which complicates things significantly as compensation for telescope altitude will have to be made somewhere). Possibly a "dome correction" can be made every minute or so, depending on the slit width.

2) Motors - In my case I am thinking of using two windscreen wiper motors on either side of the dome. This will reduce the tendency for the dome to go off-centre when the motors are activated. Transmission will be by friction, provided by cannibalized "spring clamps" (Bunnings have a range of large clamps) keeping the motors in contact with the dome's inner ring at the appropriate tension. As already mentioned, slippage should not be a problem, as another correction can be issued until the dome is pointing in the correct direction.

The only PC interface that would be required would be something that can provide a single "on-off" capability to the motors using USB (an inexpensive electronics kit possibly?).

Materials List:
a) USB Barcode scanner
b) wiper motor
c) wiper motor control (power supply, start-up etc) - electronics wizard required
d) USB interface to wiper motor control (on/off) - electronics wizard required
e) Software to
1) Read the dome azimuth output from the USB scanner software package
2) Read the telescope azimuth from ASCOM
3) Compare the dome azimuth to the telescope azimuth and issue an "on" command for a duration dependent on the difference.
4) Repeat until within error tolerance

Hopefully there are others here that would be able to refine the idea, point out issues/problems, or shoot it down (saves time going down a dead-end).

Regards
Daven

[h0ughy]

i am afraid you might be right - more money - this astronomy fettish is a money pit ;)

[thunderchildobs]

Remember to think about how to keep the slot in sync with scope after a slew. The scope is pointing in the right place, but the dome is still catching up. In an automatic imaging run you might get a few more extra light / dark frames than you were expecting. :)

The occassional "nudge" would work once the scope and slot are in place, but could be interesting when slewing.


How do you handle the situation where if imaging in the north, the dome rotates east to west going via the north, imaging in the south the dome rotates east to west going via south. Doesn't this mean the motors will need to rotate the dome anti-clockwise when looking north and clockwise when looking south. How do the motors know which way to turn the dome?

Brendan

[snowyskiesau]

How does the optional drive work? Is it a friction drive from the motor to the dome or is there a rack and pinion style drive?
Flexible racks are available but they are not cheap.

If it's a friction drive then it should not be difficult to set something up. A small 12v motor (wiper motor or similar) and a bidirectional DC motor controller driven by a suitable program via ASCOM.

[Spacetrakker]

Hi Guys,
I spent many hours/days/weeks/months agonising over a "cheap" way to motorise my Sirius Dome. I came to the conclusion that "friction" driving the dome is frought with problems due to the way the Sirius wheels allow the dome to have considerable sideways movement. ie. It is not rigidly fixed in a "track"
This then meant a "gear" drive is needed. I could not find a local (Perth)source of toothed steel rails to install round the dome base, nor a cheap drive motor/gearbox. So, my final solution was to buy the Sirius Dome Rotation Kit. (Yep! Lots of $$$ !! but it sure works nicely!)

I then persued the issue of computer controlling the dome rotation drive via a home built interface PCB to the computer serial port. There is somewhat more to this than first meets the eye. Not only do you need to interface to the computer port but you also need logic to keep track of the dome position, travel direction etc., and most difficult (for me) write the software to communicate with the Ascom software.

In the end, I solved all the issues by convincing SWMBO ("she who must be obeyed") that I would have lots of extra time to help around the house if I just spent a few extra $$$ to purchase a Maxdome kit........and she bought it!!:lol:

Now it all works beautifully

Good luck guys...not an easy problem to solve.

Cheers, John

[bert]

John did you try the lesvedome driver? Basically Lesvedome is a ascom driver that is designed to work with a velleman k8055 usb board and some relays and an encoder. The velleman board is around $120ish assembled from Ocean Controls in melbourne.

For a more in depth read the read me from here http://www.dppobservatory.net/DomeAutomation/DomeDriver.htm

I have used the lesvedome protocol on 3 different observatories, granted they were roll off's, not using the tracking function that is the heart of lesvedome. I simply used the ascom driver to control the roof/shutters via ccd autopilot (or any ascom compatible software that has observatory control like maxim dl etc) for a nights unattended imaging, its nice to know once an imaging run is over that your roof will shut automatically.

I have built a dome lesvedome system for a friend that uses the full tracking via ascom and wireless control of the shutter. Its still in the prototype stage on my bench and I have had it working. If you know a little about electronics (or can con someone from iis who does!) you could build a full telescope tracking system including motors for considerably less than maxdomes 2x pcb's and lesvedome has better control of tracking errors.

Gear drives/racks are the go.

Brett

[Spacetrakker]

Brett, thanks for that info. Unfortunately when I bought my Sirius Observatory back in 2003 I had not heard of the Lesvedome solution. In fact even after I first installed Maxdome there were quite a few issues with keeping the dome opening synchronised with the scope.(Using an Eq. mount) Fortunately most of these problems were resolved with the newer versions of the Ascom software. I'm now retired but my background is Electronic Engineering and I most certainly would have had a go using the Velleman Kit which looks great!
Good luck with your efforts.

[jase]

I faced the same dilemma. After much investigation, MaxDomeII seemed the most plausible way forward despite the cost. I did purchase a Velleman board, but I stopped heading down this path when I wanted shutter control to go fully robotic/autonomous. The whole RF comms and two stage shutter opening/closing would require further consideration as Brett alludes. If one could package up on the cheap, then they would have a winning combination. Have to say that the MaxDomeII install has been running for a year now and its been flawless.

[h0ughy]

So whats involved with the maxdomeII - does that include the hardware, motors control box etc, or just the brains?

[h0ughy]

thanks for your input John

[pmrid]

I had a look at the Sirius domes in their factory last week and it is not an exaggeration to say that it is a whole heap easier to install the automation gear at point of manufacture rather than as an after-market add-on. And I had a look at their current pricelist for the 2.4 metre dome. If you're already comfortable spending about $8 grand on a manual version, the additional $4.5K or so isn't really all that much in the larger scheme of things. It works, it'd designed for this dome, it comes with their backup and so on and so on and so on.

Peter

[jase]

MaxDomeII is just the brains Dave. I have to agree with Peter that its easier to get the motorisation kits fitted at the factory, but if you're "handy" it aint hard to retrofit a rotation and shutter kit yourself - I didn't have any problems. I have heard on the Sirius Yahoo group that the original install was quite cumbersome, but over the last 12 to 18 months the guys at Sirius have really refined the installation process. Support from the team there has been second to none. Very helpful.

[h0ughy]

thanks Jase and Peter. Have to see what to do now, 2 grand just for some brains is a bit steep, but i suppose thats because it is specialised? so it is $4.5K for the whole lot?

[h0ughy]

I just called Sirius - the full kit including the morotised shutters and rotation with Maxdome costs about $8300.00:help:

I think i might look into another alternative that has been suggested to me. i simply cant afford the Maxdome version

[asimov]

Hi David.

Do you have a link to the obs in question?

I'd love to give you some alternatives to making a cheap drive for it but I'd need pics of how the dome runs on it's track first.

[h0ughy]

http://www.iceinspace.com.au/forum/showthread.php?t=54892 this is my observatory John

[asimov]

Thanks David.

Well I guess me being a DIY kinda guy, I'd certainly take this on if it were my dome. I don't have a well paying job though, & that makes a difference.

But if it was me, I'd start like this:

Test that wiper motor. Hook the bugger up to a 12V battery & test it.

If it worked, I'd build a frame for it, comprising of a hinge system & a fairly hefty spring to put tension against the track.

The track could be something like 50 or 75mm wide by 3mm thick aluminium flat bar. It's sold in various lengths right up to 12M lengths.
The ends of this ally bar would have to be 'preset' slightly into a slight curve to match the radius of the inner surface of the dome. Nut & bolted on of course. top & bottom of the ally track leaving the centre free to allow the wiper motor wheel to run on.

It wouldn't overly matter if the track is not perfectly round. It'll only be as good as the inner surface of the dome where it'll be bolted to. This is where the beauty of the spring loaded wiper motor comes into play.

A switch mounted on the wall of the inner dome at your convenience as well as a waterproof one on the outside. A 12V battery hidden some place.

The only problem I foresee is this wiper motor perhaps turning the dome too fast or too slow.

Just a thought anyway mate.

[ChrisM]

John,
I'm also interested in this solution and am wondering what type of wheel you would envisage on the wiper motor shaft - presumably something fairly soft?

The speed could be determined (somewhat) by choice of wheel diameter, although I imagine that there will be an optimum size - given the power/torque of the motor in relation to the work that it has to do to rotate the dome.

Chris

[bmitchell82]

If the wiper motor isn't "strong" enough to move the dome you can always run a Gear reduction, similar to what you would have on a mountain bike? hell you could use a mountain bike gear system if you are handy enough. Just like a truckies knot, you can end up putting that many in youll snap the rope without too much hassle!

[bert]

Windscreen wipers have a lot of torque because of the gear reduction built into them. If a windscreen wiper cant spin your dome, there is something wrong with your dome.

They simply should not be hard to rotate, if a windscreen wiper cant move your dome, fix that before moving on with automation.

Brett