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kbrown

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About kbrown

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    Nebula

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    London
  1. Arduino Controlled Scope Fan

    I made it myself. You don't need a CNC machine for that but you do need some chemicals and a few supplies plus practise to get the process working reliably. There are several methods but the one I'm describing here works the best for my purposes. It can be messy and might not work every time but for one-offs it's quicker and cheaper than to get them done somewhere. Worth it if you do it frequently enough like I do. I do have a CNC router but I don't use it for engraving the PCB traces. I do use it to cut the PCB into shape and drill the holes which you can do without a CNC machine too if your design is simple enough. I use pre-prepared photoresist pcb laminates if possible as they're easier and quicker to deal with. Sometimes if the development goes wrong and I have to strip the photoresist layer off to start over then I use Photoresist Dry Film to get a new layer on. These are usually positive photoresists as opposed to the original negative photoresist layer so to develop it you'll need print your design inverted. Forget the photoresist sprays as it's really hard to get an even and dust free coat with them. I print my designs using a regular laser printer (set to darkest possible setting) on LaserStar PCB printing film if it has really fine lines and narrow gaps in it. If it's a simpler design with thicker lines then the cheaper laser printable tracing paper will do the trick. I use an old Phillips facial personal solarium (cheap second hand from ebay) with 4x UV lamps to expose the pcb sandwiched between two panes of window glass. After the UV exposure I develop it using universal PCB developer solution (SENO 4007) After successful development I etch the PCB in a self made etching tank which I made out of a plastic jug, a fish tank warmer and a fish tank aeration pump. So far I've been using ferric chloride to do the etching but it's quite messy and does age and loose its power over time. Once the solution I currently have has expired I'll be switching to another type of etching solution made of hydrochloric acid and hydrogen peroxide which will last longer and from what I've read should actually get better over time the more copper gets dissolved into it. After etching I usually immediately tin the bare copper (before it starts oxidising) using Seno Immerse Tinning method which is quite simple to use. It'll give extra protection to the copper layer and also makes it easier to solder. Another useful thing to do is to either add a solder mask (I've used Dynamask 5000 in the past) or use Green Coat Solder Lacquer like I did in this case. The lacquer is easier and quite durable if you follow the instructions. Either way this will protect the PCB even more and make the soldering process easier. Sometimes I want to get the component layout and annotation on the top side of the PCB. For this I've successfully used the photoresist dry film mentioned above. After developing and curing the film it's a good idea to protect it with some clear lacquer. Happy to shed more light on the details if you wish?
  2. Arduino Controlled Scope Fan

    Thank you, sir! Definitely something for the future to test. Wouldn't be hard to print the data in csv format and do some graphs. For now I just wanted to get this in some sort of usable state so I can take it with me on my upcoming holiday in few weeks time.
  3. Arduino Controlled Scope Fan

    Just got this thing in a usable shape. Mechanically and electronically I think it's pretty much done. The software running on the Arduino is preliminary but it'll do for now. It measures ambient and mirror temperatures, supply voltage and fan speed. These are printed out on the serial port for testing purposes. It won't try to run the fan if the input voltage is below 10V. The fan will run 100% speed if the temperatures differ more than 4C, 75% speed at 3-4C difference, 50% speed at 2-3C and 25% speed at 1-2C. Below 1C difference it won't bother to run the fan at all. I've just guesstimated these values as I haven't been able to test it in the field yet. Here's some pics of the fan assembly:
  4. Arduino Controlled Scope Fan

    Thanks guys. Your comments confirm what I was thinking as well! Speed control is not really necessary but I'll throw it in just to get a feel for it. I already have a tach signal from the fan and pwm input on it to control the speed. Both easy to hook up with the arduino. There's an easy to use PID controller library available too so most of the heavy lifting is already done. I think šŸ˜‰
  5. Hi, I've been working on a DIY fan for my 10" Skywatcher newt. My plan is to measure the ambient temperature and the mirror temperature with two separate thermistors and control the fan speed depending on the temperature difference. My question is, does it make sense to use the fan if for some reason the ambient temperature is higher than the mirror? The fan is sucking the air out the tube at the moment.
  6. DIY Flat Field Panel

    SGP looks like fun but sadly it's windows only. Ekos in KStars has a scheduler too to do the same. Been happy with that so far.
  7. DIY Flat Field Panel

    Good points, thank you. This won't be attached to my scope permanently for now so I'm not too worried about the weight. What is SGP?
  8. DIY Flat Field Panel

    Some progress on this. Got the panel in a picture frame and the inverter and battery pack on the back side of it. The inverter has a manual dimmer built into it so at least I can use this as is already. My long term plan for this is to have it controlled by an arduino which I can connect to from KStars/Ekos via an INDI driver. I'll probably add a dc-dc step up converter behind the battery pack to stabilize the voltage even when the battery charge starts to drop. Then after the converter I'll add an adjustable voltage regulator with a digital potentiometer the arduino can have control over. This way I should hopefully have a consistent way of taking flats with all my filters etc. Any comments / suggestions are welcome as always.
  9. DIY, High efficient narrow band camera system

    I'm not an expert but wouldn't the split beams be dimmer than the input beam thus you'd have to increase the exposure time?
  10. DIY Flat Field Panel

    Hi, So I'm about to build an EL panel based flat field generator. I've got the panel and a suitable 12V inverter already but I haven't really got a detailed plan how to put it together yet so recommendations are welcome. The panel is A3 size. A little on the big side for my 10" newt but I was going to use the whole panel anyway instead of cutting it to ensure even lighting. Maybe put it in a picture frame behind a plexi such as this: https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F172815175264 The inverter would go on the backside together with a handle of some sort. Then I'd fabricate a suitable adapter perhaps out of mdf or plywood so that it sits nicely on the scope.
  11. Triangulum Galaxy, M33

    Haha. No we went by car. It's actually quite amazing how much stuff I can fit in my two door coupe. On top of the stuff in the photo there was also her and her luggage B-)
  12. Triangulum Galaxy, M33

    It's fairly straight forward to use. Just make sure it's in focus before you go out in the dark with it. That's probably the trickiest thing with it as there's no focuser at least not in mine. For guiding settings I usually try to keep the exposure as short as possible by setting the camera gain quite high so that it responds quick. For this image I used 0.5s exposures with 85 (max 100) gain. I also have tweaked the guiding parameters a little from the defaults. I lowered the proportional gain a little and introduced some integral gain. Can't remember the exact values off top of my head. Just make sure your rig is balanced properly before you start experimenting with these sort of settings...
  13. Triangulum Galaxy, M33

    EDIT: accidently hit submit before I was ready :\ Scope: Skywatcher 250PX Mount: NEQ6 Pro Guider: 50mm skywatcher finder + QHY5L-II mono CCD: Atik 383L+ mono Astronomik LRGB filters DIY INDI focuser DIY INDI filterwheel (modified OpticStar Manual 2" wheel) Dew heater only on guider Raspberry Pi2 for INDI server KStars / Ekos for control and capture lin_guider running on the RPi2 for guiding PixInsight for processing
  14. Managed to capture about 65 (180s each) useable subexposures of the Triangulum Galaxy on my holiday. Mostly luminance but apparently enough RGB data too to bring out some colour. Not bad considering I didn't take any flat frames for calibration. More info here: https://en.wikipedia.org/wiki/Triangulum_Galaxy
  15. Strange indeed. I'm just guessing it was the moisture in the air that got in there and when it cooled down enough it condensed as dew and then eventually froze. It happened on the outside parts of of the OTA (steel tube) itself too on the same night.
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