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BAZ

A bit of Dob Modding.

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BAZ

After seeing Doc's post about rotary encoders the other day I decided to try and put one back on my Dob. It did have a older version of this and unfortunately this had errors that built up by turning it backwards and forwards. So it got taken off.

I ordered this yesterday and it turned up today, so at the weekend I will try fitting this to my Dob and see how I get on with it.

https://www.machine-dro.co.uk/rotary-angle-encoder-and-remote-display-with-a-6mm-diameter-shaft.html

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Doc

I have gone and ordered one as well Baz. Cannot fit two into the gap so have gone with one on the azimuth and the other will be a normal wixey on the altitude.

 

I hope they are more accurate then the older ones as like yourself I found them a bit hit and miss.

 

Take a few photo's and let us know how you get on.

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Tweedledee

Looking forward to seeing your progress on this Martyn. I'm very interested to see how you will transfer the rotation to the 6mm shaft. :thumbsup:

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Smithysteve

Sounds interesting. Will be be following this one... I used to use the ‘spring’ flexible coupling for encoders, which allows for a bit of movement between the shafts... this sort of thing...

https://www.amazon.co.uk/sourcingmap®-Coupling-Diameter-Aluminum-Connector/dp/B06X9YLTKD/ref=sr_1_1?ie=UTF8&qid=1507758452&sr=8-1&keywords=Encoder+spring+connector

cheers!

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BAZ

Not a bad shout there Steve, I don't know if I will have enough room under the scope base for this to fit, I'll have a look though. Thanks.

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Daz Type-R

Nice one Martyn, got to love a bit of dob fettling!

 

Watching with interest.

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Doc

You do know Baz that's on the slow boat from China. The delivery date is 30th Oct to 28th Nov.

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tuckstar

Interested to see how you get on with this. Could be the next mod for mine. Of course I'll be recruiting your help.😊

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Graham
4 hours ago, BAZ said:

If you fit that the chances of your encoder giving you an accurate repeatable readout are virtually zero. 

 

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8472

Interesting.

 

Am I right in thinking this substitutes a Dob setting circle?

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Bino-viewer

I'd quite like to add encoders to my own scope.

Are they easy to fit.....?

 

I was thinking of ordering a pair from America, something the same as on my Alt-Az

They retail at around $80 USD each i think. I could then use my Nexus DSC with it.

 

https://www.usdigital.com/products/s2

 

 

36440743574_a74949d49d_z.jpg

Edited by Bino-viewer

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Doc
1 hour ago, 8472 said:

Interesting.

 

Am I right in thinking this substitutes a Dob setting circle?

Yes Kev they are a substitute for a setting circle. If fitted correctly they are meant to be very accurate but they need to fitted well. 

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Rusty Strings

Would you expect an encoder to be more accurate (if well fitted) than a setting circle, would it remove the need to calibrate an adjustable pointer from opposite sides of the sky?

 

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Doc

I would hope it would be more accurate John. It says accurate to 0.1°, on a setting circle you would need to guess to get that close.

 

 

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BAZ
7 hours ago, Graham said:

If you fit that the chances of your encoder giving you an accurate repeatable readout are virtually zero. 

I was thinking that Graham, which is also why I am not getting it express delivery Mick.

One of the problems I found with the old encoder is that despite my best efforts to keep everything central, there was an element of eccentricity. This changed everytime I picked up and moved the base. I suspect this is where the errors were produced.

I am thinking that I won't screw the encoder to the base, but more restrain it from moving in the centre. I have an idea for this, but it will need testing before I make a chump of myself banging on about it. :ph34r:

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Doc

Sounds intriging Baz if you need any help just holla

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BAZ

Well, that didn't go as planned.

I have got the encoder mounted and working a treat, the problem is there is not enough clearance between the encoder and the bottom of the scope mirror cell. I have mounted it as low as I can get it, but the scope still hits it.

So, do I give up on the encoder and angle gauge or modify the base and raise the height of the scope to clear the encoder.  I will be making a new base at some point, so it will be a good place to start getting some basic measurements in.

I'll have a think about it and have a look tomorrow now. 

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BAZ

Jesus, If I'd known it would be this much bother I wouldn't have started. But now it's done and the encoder works a treat. Only took twenty five hours!

This morning I set about the mount and have moved the whole scope up 30mm, this is so the scope can swing back to vertical in the rocker box and now clears the encoder unit in the base.

I had to make a platform which is bolted to the Telrad bracket, so that the incoming data cable, a new 2 metre long one,  doesn't have a kink or bend in it where the plug meets the digital display unit. You can also see the original holes in the mount where the scope handles and the added bearing units were situated. I'll have to get something to fill these so the board doesn't turn to Weetabix.

You can see from the picture, how low the encoder is mounted, it's literally as low as I could get it. But now I theoretically have a readout accurate to a tenth of a degree.  

 

 

DSCF4625.JPG?raw=1

 

DSCF4626.JPG?raw=1

 

DSCF4627.JPG?raw=1

 

DSCF4628.JPG?raw=1

 

DSCF4631.JPG?raw=1

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Doc

That's a lot of work there base, increasing the height is quite involved. The encoder looks well secured and on axis so should work very well. Did you notice they put the magnets on the display box on top and not on the botton where they should be.

 

Nice one Baz.

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BAZ

Oh yeah, hence the heavy duty velcro. The magnets are pants as well, you would be better off with blue tak.

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Tweedledee

A lot of work, but it looks like you have done a grand job. It should be well worth the effort when you're using it. :thumbsup:

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Rusty Strings

Good job mate.

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