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Phobos 226

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About Phobos 226

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    Vacuum

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    Surrey, UK
  1. Having just set up one of the 0.4A 27:1 Nema 17's from stepperonline I've found it works perfectly with a DSLR and I could turn the current setting on my LV8729 right down low so everything is virtually silent while still managing more weight than I have available to add to the focuser right now. I'm happy this is future proof for whatever weight I want to add. With a direct coupling to the coarse shaft on the focuser (don't use the fine focus) on my Skywatcher Crayford I can full-step for 2.2 microns of accuracy on my f5 130PDS, which is plenty enough inside the Critical Focus Zone. As for the backlash, yes it's there but not nearly as bad as I had anticipated and it can be compensated for in software/firmware. Having absolute positional accuracy (provided no missed steps) with full-stepping, the reduction in power requirements, less heat from fully energised coils and the huge amounts of torque in reserve is an acceptable compromise for me. So there's another +1 for the 27:1 from me, if it's of any help.
  2. I didn't, but I've not been running the official Raspbian release for some time as I switched to Ubuntu Mate with Stellarmate OS and then KDE with their latest update. I never encountered any overheating or throttling problems with this case however and it stays very cool compared to running it with no fan and heatsink out on the bench/desk. I've seen a lot of recommendations for the FLIRC case though, which has a plastic bottom shield to help out the WiFi and an all aluminium core that acts as one giant heatsink that sits directly on the chip. As it's going to be in the cool night air I imagine this would be perfectly fine as well, as we're not running them stuffed away inside some entertainment centre or under a TV etc. I'll probably switch to a FLIRC case in a little while as I do like the look of the finish and it's not too expensive.
  3. It was one of these by John Sinclair but I bought it direct from his eBay store as I don't have a printer myself. The 4 can get rather hot, especially with the warm nights we had over the summer in the UK South East this year.
  4. Had a busy weekend, here are some quick phone images that I only just got around to! I just got my power distribution box finished and mounted this evening and you can see it underneath the RPI4. I've got the platform mounted in a 'wing' style at the moment as I moved my guidescope back a bit a more. The weight imbalance here is only about 200g which isn't too bad opposed to mounting it directly over the centre axis of the OTA. The platform has two mounting points with 1/4 inch UNC bolts that thread directly into the 33.5cm dovetail which had those holes pre-tapped. I added my own holes to the dovetail threaded directly into my scope rings using the same UNC threaded bolts. This is on a 130PDS and the rings that came with it as standard from Skywatcher, so they may be smaller on the SW 80ED I'm not sure, but the principle remains the same. Using an OAG you can mount the plate/platform directly over the centre of the tube so you can be a bit more flexible in your layout than me trying to get around the limited space I've got left on my setup here. Either way I'm happy with my new power box!
  5. I just did something similar with my RPI4, USB hub and my in-progress power distribution box. I mounted a long (cheap) 35cm Skywatcher dovetail onto the top of my tube rings and made a platform bolted to it from rigid 5mm thick matte black Perspex which then has my bits mounted using strips of 3M Dual Lock so I can swap parts around if I need them or not/shift the balance etc. Of course you can bolt things to it as well, but it's cheap, lightweight and easy to work with. If you wanted it more rigid then I would get some aluminium plate in place of the acrylic and bolt through as has been suggested, but with no cameras directly coupled to it I see no issues in a little flex for a distribution box on the top of the tube. P.S The RPI4 4GB is a dream running KStars, I can run everything locally on Pi now and just remote in from my 4K TV at native resolution. Works flawlessly and I'm sure you'll be happy with it too!
  6. If you're up for a project, I and many others have done full conversions of EQ5 mounts with precision steppers and pulleys using the excellent OnStep project. Total costs can be very low for a full conversion of an EQ5 at around £60-100 for the electronics, about £20-30 for the motors and another £20 for belts and pulleys. The only tricky parts are figuring out a mounting system (I used standard Nema 17 metal brackets that I drilled adjustable holes into to allow the belts and pulleys to be tensioned correctly) and potentially a bit of soldering depending on the 'kit' or controller you base the project on. You will also need to add a guide scope and camera if you want to get into guided images, but even without one some people have been able to use the 'Full Dual Axis Compensation' on OnStep with 6-9 star alignment to achieve up to 3min unguided subs on various mounts. I'm not 100% sure on the numbers on an EQ5 though as I have always guided with this setup, but even that can be achieved fairly cheaply with a converted finder and an old webcam or second hand ASI120MC/MM. I use a cheap 50mm guidescope from Svbony I got for about £50 on ebay. Overall you can end up with a system that can compete an off the shelf mount albeit with a lower weight capacity for photography, but still just about adequate for a 130PDS and DSLR which is exactly what I am using on mine right now. Of course you'll get a fair amount of dropped frames compared to a higher end solution, but as a rough guide my one of my tests was 40x300s exposures on M33 using my old 400D. Currently I'm fine turning my guiding accuracy and getting everything pin sharp, my best results so far have been a total guiding error of 1.1" RMS seen in this quick and dirty process of 17x300s test on M27 from 2019/09/06. Hope this helps open up another option for you to consider!
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