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Raspberry PI and Stellarium DIY finder


nickb2513

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I have the celestron German equatorial mount that comes as standard with the astromaster 130. I am looking at the skywatcher explorer 200p with eq5 as an upgrade though!

Have you any suggestions of how I can get the sensors like on the above vids?

Thank you

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  • 1 month later...

Hi Guys

I have a Skywatcher 150p on a EQ3-2 mount. I use a webcam in the eyepiece connected to a Raspberry Pi that streams and records video - I have it connected through the home wireless network so i can view the live video from a pc tablet or phone. So far so good. I have also recently brought a Skywatcher enhanced dual axis motor drive. The hand control an has a ST4 connection for a auto- guider. I got to thinking about installing a copy of Stellarium onto the Rpi and making a connection to the ST4 connection on the hand control so that it works as a GoTo control. Do you think this would be possible? I would welcome your thoughts.

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Interesting. You will probably have to  do some sort of PEC to linearise the encoders at some point based on the spec's. RS seem to have discontinued this one but do a different type that uses contact via a spring loaded plastic ball. It's the same sort of principle - the ball presses on the outside pushing internal "tracks" together. No hysteresis on these. It might be possible to attract and generate the pressure with some form of ball via a magnet working on the other side of the encoder.

I came across another type of encoder. It's a hall device and detects rotation of a magnet above it.  There were some pages on the web concerning "super hacks" for model servo's. 

This is one form

http://uk.rs-online.com/web/p/mechanical-rotary-encoders/7142693/

This is the chip that does the work but 16bit

http://uk.farnell.com/avago-technologies/aeat-6600-t16/encoder-magnetic-ic-16-bit-program/dp/2213639

The problem as always though is that they aren't linear so the claimed accuracy on the servo hacks is a bit misleading unless they correct it some how.

There is an interesting little program here for printing optical code wheels, also plenty of information on their use

http://www.mindspring.com/~tom2000/Delphi/Codewheel.html#Introduction

I have sometimes wondered if 2 could be used on an axis. The 2nd one geared up to interpolate the readings of the other one. It's also possible to use more than 2 optical sensors to increase the pulse rate. The quadrature one shown has 2 displaced by 1/2 an interval on the encoder wheel. Other fractions can be used as well.

John

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  • 1 month later...

this is an awesome project..nice work..tell me more about that mount...I have Meade 8" f/6 starfinder on an german eq mount. I am planning on replacing the clock drive motor with a stepper and adding a stepper on the dec shaft, along with encoders..to be be beable to drive the whole thing with a Pi in the field would be awesome

Brian K9WIS

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