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NickK

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Everything posted by NickK

  1. Thanks - I figured rather than go all out, I'd go with a manual setup. That way I'll learn more about the sky rather than the technology. It's light and seems like it will be very easy to get up and running rather than spend time setting up. Later when I'm ready I'll go for something bigger and use this as a guide scope and travel scope.
  2. I could develop something for OSX. Although I would rather do something in an ASCOM form rather than write a driver (drivers run in kernel space under OSX thus present a kernel stability/security issue). I'm considering writing a OSX form of ASCOM and I'll probably open source that. It would allow vendors to provide a simple plugin against an interface within a service - that way if the plugin stability causes a problem only the service dies (it's in the service's address space) rather than the user app (which may have important data unsaved). Applications can then easily just use a framework (a library). I could also make the library allow direct plugins for iOS in the shared file area (services aren't supported under iOS). AOSX - Astronomy on OS X.. in fact it's such a good idea I've just started it on sourceforge.
  3. Well it arrived at lunchtime! Pity it's raining and cloudy.. Vixen A80MF + Porta mount from FLO, arrived all in one piece Here's the mount without the legs extended: The 6mm and 20mm eyepieces - I can see a mid-mag purchase shortly.. There's a 90deg inverter too and an adaptor for a different size. First impression is that it's well made - although the dew shield comes off easier than the end cap! Oh.. and before anyone says anything I've been looking at getting a scope before Stargazers Live appeared I only knew about SL after it appeared on another forum and I watched it through iPlayer - not watched TV for two years now (it gets used for films only).
  4. Queue joke about GOTO toilet and rings around Uranus.. On a more serious note - I've grown my own Dorset Naga chillis for the last two years. I decided to go with a simple mount initially so that I force myself to look at the sky and not the technology. It hasn't stopped me from planning a DIY mount but for between now and then I'll star hop.
  5. Not that I want to sound like a bull in a china shop - is the unit still under warrantee?
  6. Edit.. windows calc is playing silly.. I'll do the maths once at home. I still think we can quite happily hit the 10 arc sec target Ok.. pen & pencil, that works out at 41.2529" (~104cm) for a 1 arc sec accuracy. So ~4" will give us 10 arc secs, ~8" will give us 5 arc secs. I could use a non-loaded gearing system to increase the acuracy however that would ruin the purity of it Another way is to actually drive a second disk with a solid link between them. The position of the pivot pin on each disc is different allowing the main axis disk to drive the second disc at a faster rate thus replicating gearing with having less play between the teeth (only the minute play in the bearing). Hmm 41"... long stoked cylinder.. Now there's a possibility.
  7. 4 man tent, check. 2KW oil radiator heater, check. Basic scope, on order. Ground sheets, check. 16A to 13A 10m adaptor and fuseblock - on order. Small portable fridge, may be ordered. Camping gas stove, will buy closer to the time - nothing like the smell of bacon & eggs in the morning. I'm assuming that your "spot" has your car and your tent. Reason is I'm thinking of getting a shelter too to act as a wind break and keep the rain/sun off. If I can get the model I'm interested in, it's partially closeable so I can put the heater & kettle in whilst observing Hopefully it'll fit.
  8. Also you will need to have administrator priviledges for some information (at least on ubuntu). sudo lsusb -v Then type in your root password. You should note there's additional information.
  9. I'm wondering if you could display the guide scope image onto the mouse sensor itself. The speed of motion sensing would make for a very very sensitive guide sensor too.
  10. Just to do some simple maths*, an arc second is 0.25 degrees and if the sensor is placed 4 inches from the axis centre then our resolution will be: atan((1/5000)/4) = 0.028274 degrees. So that means we can sense 1/10th of an arc second change if I have done my maths right.. So I think we have found our sensor. * - ie not making any compensation for the circular movement as the point of measurement should make this as close to be linear anyway..
  11. Back after the christmas break. I have researched the sensor as it would be stupid to start if we couldn't sense as accurately as we'd like. I'm happy to say the Avago ADNS-9500 sensor has interesting stats: Resolution: 5000 counts per inch (cpi) Framerate: 11,750 frames per second Highspeed motion detected at 150 cpi with 30G acceleration max. Max speed: 200 inches per second So, it can sense 1/5000 inch change in position every 11,750th of a second. Holy cows. It can connect via a serial SPIO bus @2MHz using 3.3v which would match the blackfin's levels nicely. Lastly the datasheet is readily available from Avago (I have it already). The datasheet contains all the physical characteristics, standard circuit design, hardware register definitions and SPIO commands to manipulate the registers. Oh, and it's found in the G500 gaming mouse which retails at £35... now where's my soldering iron.
  12. There's a big list of clubs: Astronomy Clubs in United Kingdom I'm lucky I have a couple in close proximity - one in Reading and one in Maidenhead. Ahh beaten to it
  13. Ok, I caved. My first scope I thought, rather than spend ~£2K on a VC200L+mount, that I should learn to look at the sky and not the technology. So I've bought one plus a little porta mount, figuring a fully manual setup would force me into navigating by stars rather than GOTO menu. I can then use the scope as a guide scope or travel scope later. £159.. by 18 minutes
  14. I'm interested in a spot with Electricity. It'll be one person (possibly a second) with a 4 man tent. All days. Only complication is that it's near the end of my work contract so I may turn up at a different time than planned if I have an interview.
  15. One option is creating a sundial top? You'll need to remove the mount and leave just a flat top (or with bolts to hold the sundial in place). Problem is that moving things results in setup time and to be honest you may as well spend the money on a heavy duty mount instead.
  16. Morning - not something I'm in the position to do but it may entice someone to attempt it (and see if it works). The principle is simple. Use the heat output from the Peltier heat pump to warm the scope and act as against dew. The effect should also help the peltier keep a lower temperature (in rough terms they keep a delta between the hot side and cold side - the cooler the hot side the colder the cold side). As Peltiers work they also generate thermal heat that needs removing. I've seen peltiers used in conjunction with water cooling for cooling overclocked CPUs (I had a water cooled CPU at one point) so the parts are available to make this happen from computer shops (blocks, tubing, pump, paste, 120mm radiators etc). The beauty i that the pumps are designed to run off the computer 12V power rail without too much vibration.. 1. Use a CPU water block to replace the hot side air cooling (clamp well and use a non-conducting thermal paste) 2. Use a water cooling pump sat on the ground (not on the stand) connected via standard silicon tubing. 3. Use a winding of silicon tubing around the telescope tube to act as a radiator (if this is not enough it's possible to then pass the coolant through a radiator) before it returns to the pump to be pushed through the water block again. Just a thought.. Edit: points to watch for: * Additional weight on the scope tube and mount. * Frosting on the Peltier & CCD (as the extraction of heat should be better which may cause this) * Obvious voiding of warrantee on the CCD * Use cable ties on the tube connection points to prevent pulling causing a leak * run the setup away from the optics for a day to test for leaks * use good quality anti-kink silicon to prevent it from restricting flow (this standard for watercooled computer tubing) Parts list (probably not the cheapest place but they're well known): * Pump: http://www.overclockers.co.uk/showproduct.php?prodid=WC-004-SW * Water block: http://www.overclockers.co.uk/showproduct.php?prodid=WC-080-EK * Connectors & fittings: http://www.overclockers.co.uk/productlist.php?groupid=962&catid=1529 etc etc..
  17. Keeping an eye on this as the VC200L is currently the favourite for a purchase in the new year. There have been a couple of mods for the VC200L. One is machining the spider vanes down to a slim width (I've read a few people have done this). Another is replacing the steel tube with a carbon fibre tube truss to prevent flexing and takes the loading off the side of the scope and away from the mirror completely. The steel tube is then used to act as a light guard and doesn't attach to the mirror at all either. I think it's one of the more 'adaptable' designs if you're brave enough to take a hacksaw to a £1300 scope.
  18. Interesting, I was looking for something too. Failing that I'd write something simple.
  19. No, that's TTL not USB. FDDI do a USB to TTL but there's likely to be a USB-RS232 device. The voltage levels can be 3-25V for RS232.. One interesting tip bit is that with the latest iOS version, it will refuse to supply more than 20 milliamps. This stops some plug in devices attempting to run off the iPad itself.
  20. Grr just wrote a long response and lost it (should make it open new threads on new tabs and not replace the current!). I've got the blackfin compiler chain set up in a VM with ubuntu 10.10. It's easier keeping linux self contained in a VM. I know this works as I've done this in the past. This means I can write the firmware for the blackfin in C with a little hook of blackfin assembler to get the thing working. It also allows me to get a concept star tracker up and running too. I have a servo based tracking gimble which is good enough for testing light dots reflected on a wall but not for carrying a load). I've been researching the optical sensor. Mouser.com allows orders from 1+ pieces however for the more sensitive sensors they're asking 600-1000+ minimum! I'll have a look at what mice can be hacked too. Avago is the main component manufacturer I've found - the good thing is that they have a complete data/command reference for their chips on their site. The problem is that the mass produced mice are now system-on-a-chip (SOC) devices that interface directly using USB. Great for attaching to the PC/Mac but not for latency (or a far more complicated interface to the blackfin). So we may have to go for accuracy by making the radius from the axis longer so the lower quality sensors have a chance to track the small movement. The problem is the track speed is lower too which slows positioning tracking. Junkyards would be great, the only problem is you have to go with an idea of what you're looking for, find bits that match the requirements and finally then alter the design to fit what you have. Not a problem as such, it's just we need to have a design first.. I've found FreeCAD may suit our needs for this. It's free, opensource and platform independent - for Mac/Pc/Linux. It can import/export a wide range for CAD formats too.
  21. Well to get an idea of what we're looking at, I think we need to look at some design parameters first: Accuracy Manufacturer| Model | Accuracy SkyWatcher | HEQ5 | 0.144 arc second resolution (not error!) Vixen | AXD | RA 1 arc min, DEC 10 min 10 Micron | GM4000 | Positioning ±2 arc min, tracking ±3 sec Meade | 20" | Periodic 5 arc sec, pointing 1 arc min Takahashi | EM-3500 | 2.5 arc sec Tak's is their observatory mount. *dreams* but in reality I think if I'm as good as the Vixen or getting towards the Mead then I'd be happy. We'll leave the tak for v2 (air bearings?) The error of accuracy exists from: a) the mount main baring play both cylinder baring play c) compression Let's target 10 arc sec tracking for the mount itself. Maximum payload A Vixen VC200L is ~6Kg. Add 5Kg for a refractor, imaging paraphernalia (2Kg), basic target scope 1Kg.. 14Kg so far.. Lets say a maximum of 20Kg balanced payload (±2Kg deviation as it won't be a perfect payload). We may not need this much but we do need an initial target for v1. Speed I'm happy for this to be relatively slow to seek at the moment. It'll have masses in reserve anyway. I think initially we should stick to one axis - RA, solve that then we can reuse what we know for DEC. So the next step is to: a) design the sensor system to cope with the accuracy (taking your rule of thumb this will need to detect 1 arc second RA (or 0.25deg). design a hydraulic movement system to be able to deliver 1 arc second with a 20Kg payload. This is going to be hard..
  22. Is it possible to remove a portion of light pollution (ie street lights which work on a specific wavelength) by taking an image with a filter than only allows the street light frequency through? Then you could subtract this frame from the subsequent imaging frames to reduce the stray light and improve contrast.
  23. Avionics are usually pneumatic due to weight. Stahl, who make scale trucks, sell hydraulics separately - this is where I thought I'd source the components if they're suitable. The next step is to get a pen, paper and calculator and check out the forces required to make a design. Then I have a better idea of suitability.
  24. The standard blackfin does do an interrupt driven ethernet port (although I think it's 100Mbit). However (for size reasons) the blackfin board I have doesn't break this out to the edge of the board. What the board has is a UART which can be connected to the matchport WiFi. The max speed is about 2Mbit. It's possible to get other development boards with a full set of breakouts. However for now we can live with this limitation. The main communication would be commands and state info which should work fine on 2Mbit with a few tracking pictures for debug.
  25. I was going to edit it but it locked out the post.. An initial calibration exercise would just allow the mount to have basic starting point. The down side is that the mount would not be good if it remained static (ie not tracking) for periods of time as the degree of error on starting to move would be slightly higher initially. For example the initial calibration manoeuvre would be a slow inital min, max move to find the limits (have an optical switch for the limit of movement). Once we know those we know the position using the optical flow sensors to track movement velocity and time. This means we know the axis positions. This allows the system to measure the change in axis position given changes in the valves. Next basic move would be to seek, slowly to the centre point and then perform a ever increasing spiral to get a good feel for the rate changes for the values. There's another option for hydraulics which is to have a balanced pilot to allow fluid to circulate and movement comes from an imbalance in the forces (ie the push-pull Kev pointed out). This keeps the entire system at a similar temperature and helps reduce thermal errors (although it has balance drift if not accurate).
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