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About NickK

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    White Dwarf

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    Near Guildford, UK
  1. CNC equipment

    I thought you needed some oil cycled to keep the bit and piece cool? Interesting
  2. Ahhh.. this the twist I didn't get to make it accelerate or finalise it - life got in the way. For example - steppers values only sync up at specific steps in the cycle. At 1/32 micro stepping - only at step 17 does the step sync with 1x stepping. So to switch you would need to 1/32 micro step to step 17 before switching the 1/16 etc (which is now step 9)- this also impacts the reset position: // on reset the step position homed depends on microstep mode #define RESET_HOME_STEP_POSITION_1 1 #define RESET_HOME_STEP_POSITION_2 2 #define RESET_HOME_STEP_POSITION_4 3 #define RESET_HOME_STEP_POSITION_8 5 #define RESET_HOME_STEP_POSITION_16 9 #define RESET_HOME_STEP_POSITION_32 17 Now imagine switching between micro stepping like an automatic gearbox on the car depending on the velocity of focuser- with the stepping knowing it has 400K microsteps to do it may be better to sync through to 1x stepping then operate in 32 step leaps at 1x speed before slowing down to 1/32 again for the final sets of steps. Yes - I use micro steps for counting, however the step count is a max of 0x0000-0xFFFF or 65K steps. Which when you have a 1:100 gearbox and 1/32 stepping on a 1.8deg step and 2.8 turns of the focuser .. results in about 1.6 million steps limit to limit An extreme example.. however 65K for a full range isn't good. Lastly I was researching an 'automatic' way of detecting the range of the focuser. It attempts to find each limit switch and then calculate the full range of counts. So that way it will not attempt to move and hit the limit - it already knows there's a limit that will be hit before it accepts the move. I agree the MF protocol isn't great - many of the protocols in the industry aren't designed but evolved..
  3. Interesting the DRV8834 only does 2.5-10.8V max. The reason I went with the specific stepper and DRV8825 (sorry 2285 was my mistake!) was that it handled 12-14V which means you get good back EMF resist and is easily powered from a car battery/PSU that's powering the rest of the hardware (cameras, filter wheels etc). "1.9 us; they can be as short as 1 us when using the A4988." this is something to be weary. "DRV8834 only has two pins for setting its microstep mode" the DRV8825 has three pins M0,1,2 like the 4988. So basically the DRV8834 is a low voltage high current. Whereas the 8825 is a high voltage and medium current. You need some voltage headroom to overcome the EMF so the step is a solid positive step rather than having it fail to step when under physical load. The 3.8V stepper is recommended to have 12V to step but you do need to set the chopper part of the driver to limit the current or the stepper gets really hot The other thing I was looking at is adding an IR remote control for INDI for the apple mac IR remote then you can manually move the focus without touching the scope.
  4. I'd be happy slotting into to the driver for the DRV8825 - a current chopper driver. Only thing I couldn't see at the moment in the code is the stepping sync points when micro stepping. So when you change down to 1 then 1/2 then 1/4 .. 1/32 for example the point on the stepper when the stepping align is specific to the microstepping driver. Thread, development and sources:
  5. Ahh I've already done just this! I have the INDI based moonlite controller (ODroid C2) --USB--> Arduino Uno -> DRV 8825 -> 3.8V 650mA stepper motor with 100:1 gearbox I made the moonlite focuser protocol have a few better commands. Torque on this is stupidly high - hence the need for a couple of stop switches. However it means I can hang a heavy set of cameras off the focuser. The Pentax only has a 1:1 focuser - hence the need to have both high torque and accuracy. The system can also step in 1/32. Quite happy to slot into this - can share the code if you'd like. Note entirely finished (ie it won't shift between stepping speeds) so will detect limit stops. Issue here is how to signify to INDI that the limit stop is achieved. These are some of the shortcomings of the moonlight focuser protocol.
  6. OpenCV for the QHY5 on Linux

    You may find that you need additional dependencies - sometimes you can apt get the source packages. Judging by your original post - it sounds like there's a piece of code or a configuration that is needed. Sometimes drivers installed only detect each other at start up so also worth trying a reboot.
  7. Well I'm getting bored .. with the cloudy winters night.. so I think I may pic thus up again I need some maths in my life and sometimes it's good to take a step back and view with fresh eyes. I may be also tempted to look at using AI on the residual noise layer in detecting if a pixel is noise or not. At this pixel value level, this is critical - the focus is not if this pixel is noise or not but how much of the pixel value is noise. So I will start researching the AI noise estimation and see if there's any mileage. Additionally I will start looking at some improvements for performance. I don't think it's worth hitting the GPU yet but there's definitely some algorithmic speed ups that could be done.
  8. OpenCV for the QHY5 on Linux

    Surely it's just recompiling the OpenCV .. as long as it has a back end for SIMD instructions. There is an OpenCL variant of OpenCV but the issue there is, again, the GPU code needs to be specific for the architecture to get any real performance boost - especially with the shared memory systems on embedded (such as PI and Odroid etc).
  9. I have upgraded to HS.. the install was 'interesting' with multiple restarts to get the thing operational.. I use a Odroid C2 for everything - why? because I find not have the mac available.. a pain in the behind lol! I do like the programming in OSX though.
  10. I switched away from using OSX for astro, simply because they kept changing the USB model.. causing things to break every release.
  11. Is Rotation all that bad?

    My thinking here is - if the image rate of rotation is known, it can be transformed by sampling. So you take an image Isub, that is captured during a period of Tsub when a rotation of Rarcsec rate occurs. The output image Isub has trails, however by applying sampling using grid that rotates and takes a weight based on Tsub and Rarcsec then the output is stacked into a final frame.. after derotation, the result would be a normal image. Note this is simplified in that it's a straight rotation rather than a sweep..
  12. I had an APC UPS for a home file server a while ago, very good idea considering the housemate pulled the power to plug in the vacuum.. Shutdown handling, the APC I had used a serial connection to alert the computer that the power (a) was on battery power, and (b) was reaching a critical level to trigger a graceful shutdown of the server. not many astro systems can invoke a park process, close the roof and shutdown the PC etc automatically. Noise added to output, as the 12V systems we use are sensitive to noise finding the right inverter not to add noise into a AC-DC>battery->DC-AC->PSU->12V for a camera for example is going to be worth investment of the time to look for good options. My (unqualified) thinking is that having a 12V battery being charged by a charger that leads to the 12V equipment is like having a capacitor over a motor in that it should reduce noise.. Especially with PWM style charging that limit/chop the current to shape the current delivery. Lastly - deep cycle leisure batteries would be best. Although new cars have AGM style for the stop/start functionality. Although a car battery.. I have a Bosch S5 100Ah that I have used for astro.. you can get two days of astro out of it however on the second day the noise level on the camera caused by the deeper discharge dropping the 12V line increased enough to be visible.
  13. All Sky Camera/Weather Station build

    You need a current chopper controller. The arduino and even the arduino servo shield aren't/can't deliver chopper style control. I tried the shield, I tried writing a software chopper driver but in the end the rate of current control is too low. I have a stepper rated at 3.8V 680mA and I use 12V on it with a DRV8825 (IIRC that was the number) and it sits there with no heat - you can calibrate the maximum current delivery using the variable resistor on one of the pins and at that point it will deliver 12V that firmly overcomes back EMF but limit the current so it will never burn out. The DRV also supports 1/32 micro stepping IIRC the DRV will go up to 30V with a heatsinks so can cope with pretty much anything It also have thermal other cutout protection.
  14. Pi3 Replacement

    I looked at the XU4 option. The main reason I went for the C2 was that it's passive cooled with little chance of being thermally throttled. This means there's no fan vibrations if the unit is mounted on the mount and the CPU is not going to get throttled and cause tracking/processing failures. The C2 runs ubuntu, does alignment, astrometry, star tracking, autofocus and capture with little issue of CPU performance. All of these embedded chips have a 32bit memory bus with 2GB of shared graphics/main memory - additionally the drivers aren't 100% optimal in most cases so the resulting performance differences aren't that much. The XU4 does have 8 cores and the big cores have 4x the cache.. but then linux has to cope with scheduling correctly for realtime such as tracking. As most people seem to use these for media playback systems, this isn't at the forefront of the development.
  15. Pi3 Replacement

    I'm an ODroid C2 user. No fan running ubuntu. Using the eMMC card is far far faster. Careful with the USB ports - check how much current is available. ODroid have had a couple of designs where the USB headers were supplied with less current than the max 500mA for each port. Only issue I had with my C2 was the HDMI seemed to have a dry joint, but as I run headless anyway that's no biggie. I have compiled my own fully 64 bit version of INDI, kStars, a local Astrometry.net and all the drivers. I use a 128GB SSD to store the 30 gigs of indices and any snapshot images.