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About pmlogg

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    Star Forming
  1. The current version Pulsar 2.7m appears to have a 700mm shutter. The original version was wider at 780mm. I've not tried side-by-side; I have one piggy-backed on the other, but the total height of the pair is less than your biggest scope. Of course when your scope pair is on one side or other of the mount the two scopes would no longer be side by side, but at the extreme would be above each other, reducing the effective width.
  2. For Canon cameras that do not have wifi but do have a usb socket, e.g. the 450D, VirtualHere could be an inexpensive solution. I am using it for observatory control with a PC and if using the software to provide a single wifi usb link it is free, the $49 cost is if using it for multiple usb connections. You do need hardware to act as a one-port wireless wifi router and power for it. VirtualHere recommended the GL-MT300Nv2, available recently on Amazon for £17, which works fine for me. Add a powerbank to provide usb power out and that's it. The people at VirtualHere in Australia were very helpful, even though it was the free version I am using. However the one downside is that the wireless router forms a one-to-one link with your computer so no concurrent wireless e.g. internet connection. Peter
  3. Hi Peter I've been reading the thread on automating the dome and see you mention a 2 part shutter. How are you going on with automating that ? I have a similar dome and working on the shutter.  You also mention other sensor integration, how are you planning that , if you don't mind me asking ?



    1. pmlogg



      I'm not actually doing anything about the shutter at the moment.  There is an Irish amateur astronomer who has a first model Pulsar 2.7m dome like mine.  He started from scratch and used Exploradome parts that he bought in the US and brought back to Ireland. 

      Unlike me, and more conventionally, he has the Velleman card mounted on the wall of the dome so did not need a wireless, battery operated, system for rotation.  This is a link that shows something about it.  https://www.irishastronomy.org/kunena?view=topic&catid=22&id=95329#96208 

      Exploradome have changed their system for the lower shutter to one that uses a pair of electro-hydraulic rams.  I did not have much joy getting a price from them but it does appear that they can still supply, on request, the old-style lower shutter part.  They use very expensive (but apparently very good) motors,  the cost now even higher with the very weak £. 

      It does not look impossible though to have someone skilled to replicate the actual metal hardware.  For the upper shutter you will see that Michael used parts from Exploradome's rotation system.  The acorn gear and trackway are available separately from other US sellers and are not very expensive.  On how it all works and how he did it Michael is very approachable. 

      Michael has however told me that he really doesn't use the automation of his shutter. The main reason is that he finds the weather where he is too unpredictable to rely on it closing quickly enough, even with a weather station.  As our weather in Scotland is probably no better my thinking was that spending a lot of time and money on the shutter, and then not using the automation would be a waste.  To me the manual system is easy and likely quicker than any sensible motor system.  Rotation is of course different, not having to go out to nudge the dome around during an imaging session is much more useful and I think being able to slew to new targets from indoors will be too.  I don't though have a method to automate flats which remains one of the limitations to my automation.

      Before Michael told me that about the shutter I spent quite a while looking at the option of using rams for the lower section of it.  I could not find a position for the bottom of the rams that did not involve having a pretty massive framework projecting into the dome.  I didn't try to take advice on that but there are a lot of bright people on this forum so one of them might have the expertise to advise on that sort of solution.

      Sorry not to have an actual solution for you.



  4. Many thanks for those good wishes. I have been keeping an eye on shutter plan. The 2-part shutter on my dome does complicate matters, requiring another motor and extra limit switches. My thinking has been that having my VM110 already moving with the dome, and being linked by wifi to the controlling computer, should make hard wiring to the VM110 possible. Perversely linking the cloud and rain sensors would be made harder. Thanks Peter
  5. Hugh and Alan Finally some clear sky tonight so I was able to give it a good test, not imaging but just slewing onto different targets. I had to increase the GEM offset figure in POTH to get closer to the mid-point of the shutter but other than that the slaving seems to be working exactly as required. It's such an improvement from having to hold down the button on the key fob while the dome slewed to a new target. Also positive is that the VM110 and GL-MT300Nv2 seem to draw very little power so that the power bank re-charges very quickly. On current performance I don't think that having those components powered by a battery is going to be an issue. A cold winter night's imaging will be a better test though. The Wifi link has been glitch-free too. Thanks Peter
  6. Alan Thanks for that, and again for your help. The pillow bearing is at an angle as I slightly mis-calculated when drilling the hole for the shaft through the casing. The Igus pillow bearing insert is a ball so the angle I've mounted it at makes no difference to its operation. It's there to support the encoder wheel shaft rather than exposing the encoder itself to radial forces. The two shaft bearings are also from Igus and of similar format, i.e. balls within a housing. The speeds of rotation are well within the tolerances of the bearings which do not need lubrication and won't rust. If I'd not managed to get the alignment sorted I had thought to add a second pillow bearing in that space but it would have required moving the encoder bracket backwards - and space is limited for that, or start again with a new enclosure but that would have been a lot of extra work. Luckily using the adjustment that was there with more care than the first time round did the trick as far as smooth rotation was required. I should have done more from the start to restrict axial motion of the encoder wheel shaft as I did wonder about it earlier in the process. It looks a bit Heath Robinson with the attached brackets for the Hall Effect Switch and the 2nd shaft bearing but it seems to work. In terms of cosmetic appearance I'm happier with the enclosure box for the relays and VM110. The three cable entry points have worked out pretty well. I think there is probably enough room in the enclosure for more relays if I do, in the future, want to try shutter automation. However, with the need for things to be switched on, uncovered etc. and my fear of depending on the system reacting quickly enough to close in the case of rain a powered, automated shutter is a low priority. My next stage will be to verify that the data I put into Lesvedome in respect of the mount geometry is accurate enough to maintain alignment shutter to telescope. Thanks Peter
  7. The Hall Sensor, tested with a spare magnet, registered under the K8055 programme so the encoder box was refitted, Lesvedome run and it works with the resetting to the Home Setting taking place when the Hall Effect Switch rotates past the fixed magnet. There was no time tonight to check a slaved slew nor that the other parameters I entered into Lesvedome are accurate enough for consistent alignment. That for another night. Here are pictures of the revised encoder enclosure internals and externals. I used a longer shaft which goes through the new external bracket. The space for the wheel is such that the shaft bearings above and below act as a proxy set screw, removing all but a fraction of a mm up and down motion. Also shown is the complete system other than the original Pulsar/Rigel keyfob and receiver that form the 'manual' system. The switches on top of the original Pulsar/Rigel unit are 3-way. Pushing outwards to the dome connects the new system to the battery and rotation motor. The middle position is off and the inwards positions connect the original Rigel circuit board etc. The wall mounted box contains the Velleman VM110, the relay board, UBEC 12V to 5V regulator and the connections DB9, USB and XLR for 12V from the battery and to the rotation motor. On top of the Pulsar/Rigel unit is the Powerbank and the GL.iNet GL-MT300N-V2 Mini Router. They are brought indoors for charging. Protruding from the bottom right of the Pulsar/Rigel unit is the Encoder enclosure with tensioning spring, and DB9 connecting cable. Just to the left of it, on the dome wall is the fixed magnet. It remains to be seen if the wifi link can run without dropouts but so far the signs are promising.
  8. The revised encoder enclosure with additional shaft bearing, plus extra effort on achieving alignment encoder shaft to encoder wheel shaft has been working. I had to adjust spring pressure to avoid the wheel coming off the dome wall in one part of it. So angle measurement from the encoder and slaving via Levesdome + POTH seems to be working. My measurement of dome diameter was only out by 2.1mm due to luck I'm sure. However for some reason the Hall Effect Switch wasn't reacting when passing the home position magnet (which was within range, and correctly oriented). My initial thought was that I might have a lose wire on one of the Switch's connections or that the diode in the circuit between the VM110 Digital Input 2 and the Switch's output might be blown. The diode checked out as did the wiring continuity checks. So all I've been able to do is tighten up the connections and will try again. If that fails not quite sure what to check next as everything else was working in the dome and during the indoor bench tests the Hall Effect switch was registering fine.
  9. Hugh Thanks for that image and the explanation. Yours is a much beefier encoder wheel shaft than mine (6mm). I had a look to see if there were bearings like yours available for 6mm but the smallest size was 8mm - however an option could be an 8mm to 6mm bore adapter - which Huco make. There looks to be just enough space in my enclosure for one of the 8mm pillow bearings so I'll give that some serious consideration. In the meantime I've fitted the board with the VM110, relays and UBEC into the enclosure on the dome wall and connected up the motor and battery. The test with Lesvedome user interface worked fine, wirelessly from the indoor computer, as it had done when inside with the model motor. I even managed to have CE /CCW correct. So the encoder set up looks as if it maybe the last major hurdle. The replacement encoder should arrive tomorrow but with family visiting this weekend I may not be able to make very much progress. Thanks Peter
  10. The Pulsar/Rigel rotation drive on my dome has a guide wheel which look pretty much the same as yours and it is 50mm diameter - but not sure about the bore; most of the Pulsar bolts, e.g. for the rollers on mine (quite different from those in the image) are 8mm and Paddy's photos look like they are probably 8mm.
  11. How about these as replacements? https://www.castors-online.co.uk/acatalog/80mm-Blue-Elastic-Rubber-Wheel-Only-with-12mm---Roller-Bearing---Bore-PL50WVGRBJM6.html?gclid=EAIaIQobChMI35XfqbXL4wIVTbTtCh0WKwYKEAQYASABEgKef_D_BwE
  12. As an update, back from holiday I fitted the enclosure for the VM110 and relays and did a test of the new encoder box with spring tensioner. Unfortunately the test did not go well but at least I think I know why. The encoder wheel is at the bottom of the box when it is fitted and although I have two bearings what I didn't have was anything to prevent tension or compression along the shaft of the encoder wheel passing those forces onto the encoder. I suspect that the combination of some residual misalignment plus push or pull on the encoder shaft caused it to seize. I've had a look at the design and plan to add a bracket with a bearing for the lower end of the encoder shaft to eliminate those axial forces plus an extra pillow bearing within the box. Just waiting now for delivery of a replacement EM14 encoder and more aluminium angle plate; the bearings have arrived. The older version of Lesvedome is installed and working fine with the set-up and I now have my permanent license. I also did some tidying up of the wiring, reducing the length of the cables - so its the mechanicals rather than the electrics or electronics now holding up the show! I'll post a picture of the revised box once completed. Peter
  13. pmlogg

    3/8 BOLT

    I tend to use stainless for everything astronomy and could never find a UK source. However Losmandy sell press-on plastic T handles for 3/8" UNC socket-head bolts. From their price list: T HANDLE 3/8 PLASTIC PRESS ON TEE HANDLE FOR 3/8 BOLTS $1.00 http://www.losmandy.com/pricelist.html That's what I use. I suggest buying more than you need as I certainly broke one in the process of pressing it on to the bolt head. If the postage seems too high you could perhaps email to see if they can send at a lower price via normal US Post Office in a jiffy bag rather than Fedex etc. I've done that with US suppliers before.
  14. I'm not familiar with the Nexdome but my Pulsar dome it is bolted down - in my case to a stone circle. Normal outdoor sealant was used around the dome base, that could use being redone. The centre stone of the circle isn't fitted and the connection, pier to support, is below floor level. The theory is that when we eventually move the bolts will be cut off below ground level, the gap filled and the centre stone fitted. It will have several bolt holes to be filled too but those shouldn't be too unsightly. I had the pier fabricated by a local welder. He welded a section of steel pipe to a flat plate drilled to match stainless threated rod coming up from the concrete pier base - separated from the stone circle. The top was closed off and drilled to accept a pier adapter. I had the whole lot powder coated locally. It's been fine. For flooring I used standard decking boards on top of a framework of 5cmx10cm boards. That produces an air gap underneath allowing cables to be routed under the floor from the dome wall to the pier. One of the flooring boards is hinged allowing access to the cables - which pass through holes drilled in the supporting boards. I like the decking as it never feels cold. I do get small spiders and slugs, under the floor, but they don't interfere with operation.
  15. Alan and Hugh Just a brief report as time is short. The new device arrived today - I'd forgotten we have an unplanned Amazon Prime trial. It was very quick to set up with the VirtualHere software and then connected to the main computer just as easily. Testing with K8055_dome worked with none of the glitches experienced with the Raspberry Pi. Similarly I got repeated CW and CCW movement in Lesvedome User Interface. The only glitches I did get was when I hand moved the encoder wheel - then I got a stall. So when I do return to the project in July my first step will be to go to the older version of Lesvedome. I was considering the best way to mount the device either with or without its case within the space left by the now-removed Pi but it does not have standoff holes placed for that purpose. It is however so small and in its own case that I may just use it outside the enclosure, directly attached to the powerbank and just connecting to the VM110 by usb in and out of the socket on the case. Not really much extra hassle of an evening. As I wrote before I'll post again as soon as I've made further progress. Thanks, Peter
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