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Tim Armes

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  1. Hi, I created a gallery after I saw that they were gone, with the intention of editing my post. However, I can't edit my post. I couldn't work out how to include the images inside the post without attaching them (but I wanted to embed them), so I attached them in order to upload them, then I referenced those attached files when inserting the images in the right place in my post. I assume that because they were really attached, the system deleted them during a cleanup. How should I simply upload an image to embed it in a post (rather than attach it as a file)?
  2. My images have disappeared, and I've no idea why. I also can't find a way to edit my message to put them back. Help?
  3. Tim Armes

    Equatorial platform

    My Equatorial Platform
  4. The motor has a little speed knob on it which gives a fair bit of adjustment. In my case I did the following calculation: North sector circumference: 3023mm Minutes/revolution of Earth = 24 * 60 = 1440 mm/min for north sector = 3023/1440 = 2.09 I needed to know how big my bearing diameter should be in order to work within the motor's speed range. Trying different values told me that a 16mm bearing would work: Minutes/revolution for a bearing of 16mm diameter (50.24mm circumference) = 50.24/2.09 = 23 revs/minute (which is just above the motor's slowest speed). Note that I bought the motor first in order to determine it's speed range. --- With regards to the router, in the picture the router is cutting the north sectors. You're probably confused because I'm using the end of the router bit rather than its side. The reason for that is simply because with the overhang I have over the north sectors I couldn't get the router close enough to use the side of the bit. By using a 25mm bit I could just about cut the entire thickness of the sectors. Some designs don't have this overhang, so that isn't an issue. I have it since, based on Geoff's design strategy, the Dob's feet sit directly on top of the north sectors for greatest strength and minimal flexing. Not wanting the Dob to be teetering on the edge of the platform I extended the platform over the sectors. Tim
  5. Hi, I've used 18mm ply (which seems more than sufficient for my 8" Dob's weight), and the motor is a Celestron DC motor (sold for their equatorial mounts). For the jig I had to be careful about the piece that holds the board to the rotating pole. I drew it out in Sketchup to make sure that I got the edge lengths perfectly correct in order to ensure that the center of rotation was about the polar axis. Tim
  6. A cut out switch would be nice. In my case there are screws at the end of each sector (holding down the metal strips) that should act as barriers to that problem. I should try it though
  7. Hi, A couple of years ago I started work on an equatorial platform for my 8" Dobsonian, however the project got put on the back burner because I didn't have either the necessary tools nor the woodworking experience to do the job well. This week, however, I started again. I now have a working platform (it just needs a coat of paint). To design the table I made extensive use of the paper entitled "Geometric Method for Designing a Minimum Height, Vertical North Sector (VNS) Equatorial Platform" by Gene A Baraff. Those interested will find this paper in the "eqplatforms" Yahoo group, along with a Excel file to do the calculations.Armed with all the information needed, I created a platform design using Adobe Illustrator and then printed the template to scale (tiling it across several pieces of A4 paper). This was used as the template for cutting the wood and positioning the sectors.The jig is, without a doubt, the most awkward part of the build. I had a dismantled light table that I once built in a previous life, so I repurposed that in order to create a rotational axis on which I could attach the platform. During my first attempt (2 years ago) I tried to use a sander to for the sectors - however the result was very poor. This time round I used a router (since I have one now). You can see the platform clamped on here:I built a mount to hold the router firmly at the right angle on the other side: (Note that building the router holder was an interesting problem in its own right) The Excel spreadsheet mentioned above generates a image of the theoretical curve that should be produced. By printing that to scale I was able to verify that my jig was performing correctly - and I was delighted when my sectors came out to be exactly the same as the printed ones Although the jig was the hardest part of the build, there was another part of the project which caused problems - the bearings and bearing holders. I scoured the internet for solutions, but it wasn't easy to find a product that would works well. In the end I discovered that I had a neighbour that worked in a machine shop turning metal (!), andhe was able to create the bearings and holders for me. Anyhow, it ended up taking about 2 days to build, and I tested it last night to my great satisfaction
  8. Hi, That's the Celestron that I referred to in my post. Out of interest, how do you find the noise and battery life?
  9. Hi. Yep, that's the Celestron I believe. I'm just wondering if there are better options readily available.
  10. Hi, I'm about to embark on a project to make myself an equatorial mount for my Dob. I'm trying to find out what options would be available for me with regards to the motor. Can any suggest any decent options bearing the following in mind: I know nothing about electronics, so I'm not interested to buying a bear motor and trying to make my own controller. In a perfect world, it would be a stepper motor with a adjustable speed. None of those that I've seen can be finely adjusted, they just ofter a fixed speed with x2 and x8 acceleration. It should have an axle that I can use to drive a bearing. There's not much I can do with just a cog that sticks out. It should really be designed for this sort of use due to the very slow rotations speeds. Gearboxes are an added expense that I don't need... The one that I've seen suggested before is the Celestron Logic. It's not a stepper but other than that it seems like a reasonable option. There's also a Skywatcher one that looks similar: http://www.teleskop-express.de/shop/product_info.php/info/p394_Skywatcher-Tracking-Motor-for-EQ-1.html Apparently the Celestron version has a bushing attached to the axel that's convenient for my purposes. Can anyone tell me if this Skywatcher motor also has one? The big disadvantage of these is the 9v battery. I'd rather use a set of AA so that I can recharge them. Are there other options that I'm missing? Regards, Tim
  11. Hi all, Thank you all for your replies. I thought I'd receive email notifications to this thread, but alas I did not and so i hadn't noticed all your good advice come through. I'm still considering my options for a second scope. I've also started looking at building myself a equatorial platform; that looks like fun Tim
  12. Thanks for your replies, there's food for thought there. Will - I'd not considered an equatorial platform for the dob. On any case having now discovered them I'll certainly be looking at that option for myself - looks like a fun DIY project too! Luke - it's a good question concerning the EQ mount rather than an Alt-Az. I suppose I just like the mechanical beauty and general cleverness of the EQ design. Also, I tend to associate Alt-Az with GoTo scopes, although it's clearly possible to get a motorized one without the rest of the electronics that take the fun away For a given price would I get a much better scope with one type of mount over the other?
  13. Hi, I'm a happy owner of a 200mm Meade dob. However, my young kids are often asking to look at the planets, and the Dob isn't really idea for a number of reasons: 1) I can't just quickly get it out and use it since it really needs to be left outside for a good while first 2) Since it doesn't follow the sky the objects pass too quickly for them to see anything 3) They tend to jog it and knock the object out of view So, while I'm going to keep it for my own deep sky viewing, I'm thinking of getting another scope for planetary objects. It should have a decent EQ mount, preferable motorized, be nice and portable and quick to set up. I'm not interested in GoTo because I enjoy the chase. I don't really follow gear advancements so I don't know where to start or which makes are worth looking at. Can anywise please suggest a decent scope that meets the bill? I'd rather pay to buy something of quality that'll last me a good while, but I'm not looking to break the bank either. Thanks, Tim
  14. Hi all, I've just got back from a holiday visiting family in the UK. Whenever I go back, I have to make a visit to Waterstones to enjoy browsing through books - France has no equivalents. This time I was hoping to find some interesting astronomy books. Their collection was generally disappointing, however I did find this little gem: 50 Ideas You Really Need to Know: Universe: Amazon.co.uk: Joanne Baker: Books At first I wasn't sure that it would really contain any useful information, but for the price I thought I'd give it a chance. I'm really glad I did. Although none of subjects in the book were new to me, there were plenty of details and facts that I simply didn't know. Also, it was really nice to get a refresher on some of the subject areas. A fascinating yet easy read - highly recommended. Tim
  15. Hi Guys, I'm still deliberating - and struggling - with a good choice of eye pieces. I've have just discovered that the Meade SWAs, which generally seem highly regarded, have been phased out. As a result there's still available from some shops for great prices. I thought I'd get a low power one while I still can, but I'm unsure of the most useful power to get. I can find the following: 20mm (60x), 24mm (50x), 28mm (44x), 34mm (35x) Bearing in mind that I already have a 16mm, which of the above would you think I'd find most useful? I also planning getting a 8mm -10mm something-or-other and perhaps a 2x Barlow. Tim
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