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About saac

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    Proto Star

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  1. Galloway Autumn Star Camp 2017

    Well done guys, that's the Dunkirk spirit, good to see it's still alive. Jim
  2. 2018 Quiz

    "High altitude skateboard maintenance" - man I knew I should have done that OU course. Jim
  3. AstroBaby does a good guide, you may already have seen it but here's a link just in case. Jim AstroBaby - Polar Ailgnment
  4. I'd agree with Spill above don't worry overly about an exact alignment at this stage. Unless you are ready to undertake long exposures with guiding then just do a rough alignment and spend more time enjoying the sky. When I started I didn't even bother with the polar scope (couldn't be bothered keeling on cold wet ground). I just did a rough alignment using the scope itself and a compass. Once you get more confident and itchy for getting longer exposures then you can look to refine your alignment. If you really feel the urge to spend more money then think about purchasing PoleMaster it's a great bit of kit - bit don't buy it yet there is absolutely no need. Jim Jim
  5. Can you see stars in other galaxies?

    Henrietta Leavitt, it's a great shame that she didn't get the credit she was due. Much like the Jocelyn Bell of here time. Jim
  6. Fed up.

    Erla invest your time with the young uns that's where the true joy in life is and they grow up so fast. Good decision on keeping your kit, you'll come back to it don't worry. Hope to see you around here in time to come. Jim
  7. 16 " Open Truss Dobsonian Build

    Cheers Alan. I did briefly consider sleeping in the car with it but my wife threatend to turn it into kindling if I did Jim
  8. 16 " Open Truss Dobsonian Build

    You made me laugh Mike. The first time I took the mirror into school was way back in February. Back then it was just the mirror box but I placed it in the car overnight. When I got to work and removed the lid the mirror was all frosted up, it took hours to clear! Jim
  9. 16 " Open Truss Dobsonian Build

    Thanks Mike, I hope it works well. I promised the pupils at school today to give them an early look at it even though it still needs finishing touches and a shake down. So it's packed up in the boot of the car, I feel like I should be putting a blanket around it Jim
  10. 16 " Open Truss Dobsonian Build

    Damian, niallk, thanks. In the short time I had to play with it on Sunday night I got the impression that there is a bit of a learning curve ahead of me on setting up and on using it effectively. Stand by for lots of questions and me looking for tips. I feel like I'm preparing for a Dob driving licence Jim
  11. 16 " Open Truss Dobsonian Build

    Thanks brantuk, it really has been an enjoyable project. Yes, I'm looking to stain it then put a clear satin varnish on it. I'm hesitating at the moment trying to find a decent wood stain/dye - I'm too indecisive. The ones I've found in the usual high street DIY chains all seem to be non alcohol based - the dye doesn't seem to penetrate the wood very well. The one I'm trying out at the moment is Coloron Wood Dye - a chestnut colour. I also need to flock the inside of the upper OTA and paint the inside of the mirror box black. I think the alt axis is fairly stable at the moment but it will need a proper shake down to expose any problems. I think you are right about a brace though between the two bearings. I think it would certainly do no harm but I'm worried it may detract from the clean lines of the circular box and bearings. I'll see how it performs once we start using it properly then make a decision, but I wouldn't be surprised if I end up adding a bracing bar or two. There may be a slight wobble between the two ground boards at lower elevations - I think it bounces a little when its moved in lower elevations. I think it can be solved with perhaps a few more contact points between the two circular boards - I've used teflon furniture gliders. Either that or a heavy mass sitting on the ground board but I'll try to avoid that. What I really need now is a good run of clear skys and decent weather to shake it down and find out how to use it. Jim
  12. 16 " Open Truss Dobsonian Build

    Yes the video camera of course, I was concentrating so much on getting the scope ready I forgot about that, thanks Andrew. While the kids will definitely want to get their eye to the eyepiece the video camera will be ideal for group sessions. To be honest the height of the scope just adds to the drama, it's going to look really impressive in the classroom. I took a fresh look at the VS focuser last night and it is a capable bit of kit but it is a bit heavy. I think I'm going to use it as a vertical stage for our DIY interferometer - it already has as good xy stage but lacks fine motion control in height adjustment (z axis). The VS will be more than up for the job. As for the effort - well what can I say, I spectacularly underestimated just how much time this would soak up. It has however been wholly enjoyable and very satisfying; you should have seen my face when I got the upper OTA secured on the truss tubes and had it fully assembled for the first time. I was skipping around the garden like a 12 year year old Photographs to follow of our first outing with it hopefully early December. Jim
  13. 16 " Open Truss Dobsonian Build

    Hurrah - it flys We had a clear night in Fife yesterday and I finally managed to set up a temporary jig so that I could measure and cut the truss tubes, wasn't easy but we got there. I took the scope out tonight and although the collimation is way out I was relieved that it could get the stars in focus. A couple of immediate observations: 1. Movement and balance - movement is nice and smooth, no jerking in either axis. Despite my concerns about the weight of the mirror box, the large moment arm means the scope is a little top heavy. It balanced perfectly with a 2lb lump hammer hanging from the box (hey it was easy to hand) so should be a relatively easy fix (i'll use something more refined than my lump hammer). 2. Moonlite connectors - performing really well although the tri point knobs for tightening the tubes in their sockets are not suitable for cold dark Scottish nights. They are too small, fiddly and the pointed ends really hurt against freezing cold fingers. I can see these being replaced with some round rubberised knobs. 3. It's big ! I need to rotate the upper tube so that the focuser is in a more convenient position for viewing (easy fix) . Notwithstanding that, the scope at F5, places the eyepiece well above eye-line of your average Scottish astronomer! Our diminutive height up here helps when running down haggis on the hills but not so good for tall telescopes Some form of suitable step will need to accompany the scope. 4. Setup - connecting the upper tube to the truss tubes and then to the lower assembly was a bit tricky - as one tube was located in a socket another would pop out. Maybe it was because it was the first time but it was a wee bit frustrating, there is probably a routine that works best so I'll figure it out. Strike down was really simple - took about 10 minutes to have it all packed away and back in the house. Ok so some fettling to do before I can take it into school. Apart from getting the scope stained and varnished, I need to sort out collimation and fashion some sort of shroud. December is looking good for our first star party, a nice Christmas treat. I'ts been hard work, about a year in total since picking the mirror up from Andrew, but it's a really great feeling getting to this stage, I'm quite excited about getting it into school its going to be a real talking point in class and it will certainly add something extra special to our courses. I'll be using the mirror on its own next week with the Higher Physics class as we look at refraction (Snell's law) - our trial at Schlieren photography (see earlier post) worked really well so I'm looking to incorporate it as an enhancement to our normal practical work. We are getting there Andrew, I now just need to work out how to mount that massive Van Slyke Inst focuser as well Jim
  14. Farewell to Green Witch

    Sad to see Green Witch go , always found their service second to none. Enjoy your retirement guys. Jim