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kbrown

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Everything posted by kbrown

  1. I'm considering getting the Baader Mark-III Coma Corrector to replace my old SW 0.9x CC. Just wondering if anyone with the Baader Mark-III Coma Corrector could measure me the depth of the M48x0.75 thread? I couldn't find this information anywhere... Cheers, Kari
  2. Not quite the helical focuser I first had in mind but I had a rummage in my (one of many) random bits and bobs box and found these small bearings. I thought why not run a screw through them and have the drawtube ride along it. A couple of days later I had designed and printed this: It's a little wobbly when unlocked due to the one sided support design but once locked it doesn't move. Not perfect but I think it'll do just fine for this purpose:
  3. Before I had the "luxury" of a suburb (Bortle 8/9) back garden, I used to drive out to a number of dark(er) sky locations outside London with my kit. I tried to find places I could easily set it up right next to my car. I don't know why but almost every time I felt like I was doing something semi-criminal by doing so. Maybe it's because I come from Finland where we have this thing called (for the lack of better translation) "freedom to roam" written in law which for example grants permission to wild camp nearly anywhere given you're not going to do any damage to the nature. In the UK you generally don't have that... Anyway, I found a good few places I used to go to regularly. Most of the time all of them were okay but each one of them had their own "weird encounters" too. In one place it was drunken youth and boy racers, in another it was creepy individuals (probably "doggers") loitering around. In one place I almost always got a visit from the local police wondering what I was up to. Probably because of the relative proximity of an airport and/or a nuclear power plant. It's a shame it's so difficult to find a place you could just enjoy the night sky without the extra stress. Maybe we as a community should try to organise something? Buy an abandoned farm somewhere rural and just dedicate it to astronomy....
  4. Before inventing the wheel again, I thought I'd ask whether anyone has come across a good DIY focuser for an OAG camera? I could just get something like this but the inner maker in me wants to 3D print something useful
  5. I did the rowan belt mod myself and documented it on utube. This was the first and only time I've done it so not claiming to be an expert on the subject. At times it was a bit fiddly job but I'm glad I did it. Another worthwhile upgrade I've done afterwards was to replace the counterweight shaft with this. The original shaft has a nasty "backlash" type of wobble feature in certain orientations due to the design of the locking mechanism. The upgrade got rid of that problem completely.
  6. I don't know a lot about this but just wondering whether your test mirror is aluminized/silvered or bare glass. I'd imagine you'd typically test bare glass and testing a finished mirror will look a lot different in terms of brightness/contrast?
  7. This has been probably done before a million times but here's my take on T2 to C-Mount adapter that fits directly on many ZWO cameras. I've tested this on my ASI 183MC Pro and it works perfectly with the 25mm and 50mm C-mount lenses I have. I tried to make a CS mount adapter too but it seems like a mission impossible as the back of the lens would crash into the sensor window due to the 5mm shorter back focus length. STL attached. ZWO_T2_to_CS_adapter_v003.stl.zip
  8. When I started with my 10" SW newt, I didn't have any dew heaters on it. But sure enough on a few clear but humid nights I got dew and even frost on the secondary mirror. Primary mirror has been fine so far... Anyway. Dew shield on a newt... maybe... but sounds a bit clunky. I already have heater wires and also wires to a digital temperature sensor running into the secondary mirror holder plus a DIY heater controller that can maintain a set temperature based on dew point calculated from measured humidity and ambient temperature. Just wondering about what would be the best way to heat up the mirror without too many things in the way. Here's a picture of what I currently have and what I was suggesting in the first post. Thoughts?
  9. Just thinking aloud what might be the best way to have a dew heater on the secondary mirror of a Newtonian? In the past I have had nichrome wire wrapped around the stalk of the mirror holder but while it sort of worked, it wasn't very efficient way of doing it. Right now I've made an aluminum backing plate of the same size and shape as my secondary and the nichrome wire is sitting in a sort of a spiral groove I've routed into it. It works better but I still feel it's not the best solution since the mirror is glued to the plate with three blobs of silicone so the heat doesn't get conducted to it efficiently or evenly. Has anyone tried to wrap nichrome wire directly around the edge of the secondary mirror so it would be in direct contact with the glass? Any other great ideas?
  10. I've successfully printed a lot of 0.75mm pitch threads in various sizes with my Prusa Mk3 with a 0.25mm nozzle and 0.1mm layer height in PETG. Haven't tried 0.6mm pitch though. What I find often is that I have to print external threads a little smaller than the nominal size and internal ones a bit bigger to have a smooth running tolerance between them. Not sure if you've seen this already in another thread but I made a simple macro for FreeCAD for making metric threads of any diameter and pitch. It has a "tolerance" parameter you can play with to get a good fit for your prints: thredster.zip Note if you choose internal thread mode in the macro, it will give you a cutter to be used in a boolean operation to make your actual thread.
  11. Tilt and flex would be my first concerns like others have pointed out. Especially if you plan to stick a heavy camera behind it. Another thing is clearances inside the wheel. Too tight and a bit of flex in the casing or not so accurate bearings etc might cause the carousel to catch. Too much clearances might cause the carousel to wobble and cause all sorts of issues...The challenge is to keep the whole thing as thin as possible while being rigid enough. In the past I started designing and making a filterwheel using aluminium parts machined with my CNC router. In the end I abandoned the project due to too many mechanical issues. I didn't want to have something stuck on my scope that would cause lost imaging sessions. In the end I went via the manual to motorized route which is still working perfectly.
  12. I used to drive to dark(er) sky sites with my rig hence my car battery approach. But as I said over time it became less and less effective. These days I just use my rig in our back garden where I have mains available. Instead of shelling out for a mains powered power supply I simply just keep my CTEK battery charger on the battery all the time. Works well and I didn't have to buy anything new...
  13. I was thinking the same as @Peter Drew above. What would you gain with the conversion? Surely you're getting a bigger obstruction than a secondary mirror? Also how would you collimate this?
  14. Not sure how much torque is required in this application so this might not be suitable: I have successfully modelled (FreeCAD + Gears add-on) and 3D printed timing pinions and pulleys. I always used helicoil style thread inserts for the grub screws. Can't tighten them too much as it's easy to break or deform them by doing so.
  15. I used a 42Ah car battery successfully for a while. But since it was just an ordinary lead acid battery, it didn't like to be discharged periodically so much, As a result it started sulfating and it's capacity dropped and dropped over time. So make sure you get at least a deep cycle battery. Also keep it topped up when not in use.
  16. Can't say anything about the products mentioned here but here's my £0.02: I once bought an aftermarket 12V to 19V car laptop charger that was meant for my laptop back then. While it technically worked it only did so if the car was running i.e. the actual voltage of the 12V system was around 13.8V. As soon as you turned the car off, it would stop charging. I can see the point why they've done it this way but it was really disappointing to find out... I've also had various cheap DC-DC step up converters and while on the multimeter they look like they're producing the specified RMS DC voltage, they're actually pumping out quite ugly looking square wave ripple especially under heavy loads...
  17. Hi, A few people have asked me about this so I thought I'd update this thread. This is a very old project of mine which I did while I was still learning a thing or two about making these sort of devices. I have not documented this properly and to be honest I should really rewrite the software and firmware before doing so as so many things have changed. That said I have zipped up and attached the files that may or may not be helpful here: frankenwheely.zip Your mileage may vary...
  18. This is how I've always thought about them too...
  19. I might be wrong but honestly I don't think so. The screws got plastic tips on them which just sit int the groove of the focuser tube. I think they're just meant for locking the tube in place. I don't think they are meant for adjusting it. Mine's been totally fine after I opened it...
  20. The focuser itself is my BullsEye Focuser I posted a while back: http://knowhere.myqnapcloud.com/WordPress/2021/09/04/bullseye-diy-focuser/ For this I used a small 6Nm NEMA 11 stepper motor. Gears and the bracket are all 3D printed also. All designed in FreeCAD.
  21. I have been using those for many projects and for most parts they work okay. There's a few things that I don't like about them: - The plastic shroud is typically quite flimsy and doesn't offer much of tension release for the wire. - The cheaper ones don't have a good connection between the metallic parts and can become even worse over time depending on the mechanical strain they're exposed to. - Some of them even fail to make a good connection between the male plug and female socket. I've had to throw away quite a few because of this. Don't get me wrong. I still use a lot of them and they can be good. It's just that I've come across too many not so good ones. I think for future projects I will favor the GX12 style aviation connectors. They'll take up a little bit more space but I think it's a fair sacrifice...
  22. Suppose you could put a sachet of silica gel in the enclosure too and replace / recharge it every now and then...
  23. I tried to get it stay on just as a tight push fit but it just kept popping off as the edge of the focuser ring is beveled and there's not much to grab onto. Thought of double sided tape but I don't think that would have worked very well. In the end I just glued it on with four drops of superglue.
  24. It looks a bit ridiculous but does the job well. The one thing that has put me off from doing more wide field imaging with my lenses is the lack focus control. It's quite fiddly to do manually with some lenses. Can't wait to test this out
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