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About kbrown

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  1. The new stepper arrived today and does seem to do the job well even at 32 microsteps. I had this test running for several minutes and the dial gauge always stopped at the same spots. Feels like this will work nicely now!
  2. Did a bit more pondering and experimenting with this. The rated torque of the stepper motor in the above video is supposed to be 26Ncm which feels just about enough with the 16th microsteps I was running it with (AFAIR). But it didn't take much resistance by hand for it to start skipping steps which was a bit of a bummer. Just as an experiment I also tried with another NEMA17 motor that was rated about 19.8Ncm. This wasn't enough to move the focuser without helping it by hand at all so I guess I'm just above the threshold with the 26Ncm motor. I'm currently waiting for a delivery for yet
  3. Gave a NEMA 17 stepper a go and it's much better. Think I will go with it and re-design the enclosure around it. Here's a quick test:
  4. This is the first time I'm using a TMC2209 driver and the TMCStepper Arduino library so I'm not too familiar with it yet. I'm trying to configure it via the UART interface which gives me loads of options but in regards microstepping I haven't been able to really go below 8 microsteps as it seems to start misbehaving even without any load. So far I've had the best results with 16 or 32 microsteps. I know in theory I should get more torque with native steps but I'm not sure if that's the case with the TMC2209.
  5. Had another look at the specs of the motor I have and it's rated 0.67A @ 6.2V so I'm already nearly double the voltage driving it with 12V. Increased the current going into it as much as I dared and it did start moving the focuser but it was occasionally skipping steps and got rather hot too. Think I'll try a NEMA 17 stepper which I already have to see if it's better. Just need to print a new L-Bracket for it.
  6. Ouch. Ran into a bit of a road block with this. Turns out my chosen NEMA 11 12Ncm motor is not quite strong enough to drive the focuser attached directly on the (coarse side) of the focuser shaft. It very nearly works with a bit of help by hand but not on its own. Not even with some over current and slow acceleration etc... Bummer... So back to drawing board. A few options I can think of include: Use a bigger and stronger stepper (NEMA 17 for example) the same way on the coarse side of the focuser shaft. Use the existing NEMA 11 stepper on the 10:1 side of the focuser and d
  7. Had some issues with the focuser of my nearly new FLT 91. I think I got it working properly now. Wrote a google doc about it: https://tinyurl.com/jzh8n85x
  8. Decided to make another DIY electronic focuser for my new WO FLT 91. It will be Arduino Nano based again but this time I'll be using a Trinamic TMC2209 based stepper driver (Same as in my Prusa Mk3). The focuser on the scope is a rack and pinion style and I'll be driving it with a flexible coupler directly on the focuser shaft. I'm hoping to utilise the Stall Guard feature of the TMC2209 to auto-home the focuser and also as sensorless limit switch. I'll be adding a Class A PT100 based RTD as well to measure the focuser temperature. I found one with M4 thread that I can bolt directly on the foc
  9. To my surprise I wasn't able to focus in enough with my recently acquired WO FLT91 using my Ascension 2" star diagonal. Since all my EPs are 1.25" I decided to remove the 2" holder and printed a M48x0.75 to M51x1.0 adapter so I could stick the 1.25" holder directly to the diagonal. This gave me an extra 18mm inward travel and I was able to focus with all my EPs STL attached... The removed 2" holder on the left... DiagonalEPHolder_v004.stl.zip
  10. Answering my own question as I received this information from WO: "Focuser loading capacity is around 8-10Lbs. If you have a heavy loading you will need to add some extra tension using two screws located on the top of the focuser."
  11. I just received mine yesterday. Only been able to test it a little bit visually tonight between the patches of clouds. Here's my initial thoughts: Feels like a solidly built piece of kit. Focuser had some rough spots when going through from one extreme to another. A bit of silicone grease on the rack took care of that. Didn't have to adjust any screws. Was surprised not to be able to focus in enough with my Ascension 2" 90° Dielectric Star Diagonal using any of my 1.25" eye pieces. Had to "shorten" the diagonal by 18mm by printing a new EP holder for it. Overall I'm v
  12. Can any of you give me an idea what sort of weight the focuser on the WO FLT91 can handle? I think this is my current favourite to get.
  13. I have collimation experience only on a newtonian and to be honest it's not really that hard to do... Sort of have become part of the routine for me at the beginning of each session. RCT might be more time consuming though... Oh and refractors can be out of whack too...
  14. I haven't used rack and pinion focuser before either. I was going to add a motor focuser anyway. Most likey a DIY one as I've done before on my newt. So I guess you left the tension knob rather loose when you added the motor focuser and relied it to hold the position more than anything else? That is a bit surprising to hear. I initially wasn't going to get the dedicated flattener as I already have a HoTech SCA Field Flattener that should work with this in theory. Hmm... Certainly food for thought. Thank you! I will have a closer look now! Cheers, K
  15. Hi, I'm seriously considering purchasing a SharpStar 94EDPH. A couple of questions that I haven't been able to find answers to still remain though: 1. What is the maximum payload on the focuser? Or how much does your imaging combo weigh and have you had any problems with it? 2. Are the lens cell and/or focuser adjustable or fixed i.e. is it possible to collimate the scope to any degree? 3. Did you feel it needed collimation out of the box? 4. Any reason why not to buy this scope? Thanks, Kari
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