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Digital setting circle for Dob


Guest beewolf
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Guest beewolf

Just finished a prototype digital setting circle for my skyliner 200.  After a bit of head scratching the method of mounting is now sorted and I reckon I could do another in less than an hour!


 


Advantage is less work than an analogue one, possibly cheaper (total about £20) and the only mod to the base is 4 screw holes.


 


Haven't tested in in earnest yet but we zeroed it and the wixey on the lookout post at the top of Burrough Hill (about 7 miles away) and then moved the scope around.  When we repositioned at zero it was back centrally in field of view.


 


If anyone is interested I will try to post a how-to.


 


setting_circle1.jpg


 


 


setting_circle2.jpg


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


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That looks interesting Gavin. 


 


Just a thought, Mark two points, one on the base, and one on the rotary table. Then zero the gauge, and rotate it back and forward and then back to where the two points are are. Check and see if the gauge is still reading accurately.


I had a Bevel box remote angle sensor, but doing this it ended up miles out.


If it is accurate, post a link for the gauge. :)

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I do like that - what is the guage Gavin and do you have a link to it please? I'd like to velcro one onto my dob and test it's accuracy. Might save me a lot of dosh. Is it just an electronic compass? :)


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That looks quite good, will be interested to see how accurate it is. These setting circles for dobs are great, mine is fantastic and such a simple design, surprising that they work so well.

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Well, the video really demonstrates it's accuracy. The one I had would have been so far out by then, it could have gone round the clock. It started with a small error and just seemed to amplify the error.


 


I like that, a really neat job. Thanks for the video and write up.


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Guest beewolf

If anyone would like to have a go at this but is daunted by the plastic work I could probably help with that. Only trouble is I've run out of scrap white boards at the moment so it would have to be red, green, blue or yellow!

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In my dob the pivot bolt does not screw into the baseboard, it goes through a bush in the baseboard and has a bearing washer over the bolt and is secured by a nylon nut.


 


This way the topboard rotates freely from the baseboard.


 


So in theory the above will work fine.


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Guest beewolf

It does rely on the nyloc nut to transmit the rotation through to the bolt.  This seems to work fine in practice with no creep so I don't see a need to complicate it further at the moment.


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It does rely on the nyloc nut to transmit the rotation through to the bolt.  This seems to work fine in practice with no creep so I don't see a need to complicate it further at the moment.

Gavin,

 

Did you look into taking off the two rulers - Mine is a Trend (all Chinese!) and has a hidden screw at the center under the label which appears to hold the bottom ruler.

I realise that the top one must be fixed to the top board but I hate abusing things so I was looking to replace the the two rules rather than chop them. Just wondering if there is something i need to know that would mean that's impractical and not worth it doing - like it wont work anymore.

 

Thanks

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