Hi Dave,
great to see innovation....!
I've been a Mel Bartels (the man for innovation) software & control box user for 6 years and can pretty much tune in any 4 phase, 5/6 wire stepper with his software, so I know what you're trying to do here.
Not an easy feat with a set speed motor controller though.
There's so many things you'll have to get right here.....
To make your tracker work/ track better, I think that perhaps you would need to be well polar aligned... although at such large fields of view with your setup, it would not have to be exact. Take a series of say 10 10sec images, blink them together and see if the motors are compensating too much for earth rotation or too little in RA (azimuth). Make sure there's no movement in DEC (altitude) axis, then you'll know exactly where you are.
Lengthen your timber which the camera sits on, related to thread/ motor to slow things down or shorten the timber to speed things up. This is an over simplified method... Perhaps even reduce the voltage to the motor or increase it slightly to compensate... I know they will take less voltage, over voltage is something I'm not too sure of with these little motors.
Also if you have a noisy power supply, this can cause spikes and thus relate to jumps..... perhaps use a car battery for clean power supply.
There's actually formula to work all this out but you'll have to know your gear ratio, steps per full step of your motor and the pitch ratio of your threaded rod.
Also, if there is any binding in your threaded stud, this will relate to 'little jumps' with the stars in your tracking. This has got to run smooth. You could try lubrication and see if this improves things..
Here's probably where you got the idea from...
http://www.jlc.net/~force5/Astro/ATM/Barndoor/barndoor.html
If your keen on building say a control box and using a laptop/ pc controlled system with a stepper motor, Here's Mel's site that you might find useful...
Lots of design innovation can be found from this site... you don't have to use a control box, there's guys who've done as you... just search around the site and find the links to other peoples sites.
http://www.bbastrodesigns.com/BBAstr...ted_Telescopes
3 min is probably a little too ambitious but good for testing I guess..... If you only want to see where this little setup can take you... and since your probably just using the standard canon lens, keep you exposures down to around 1min, or to where there is no obvious trailing on the stars and stack a heap.... Keep you aperture stopped down a bit (reduce star bloat) and increase your ASA... experiment and see where it takes you and what you can produce.
All good fun though and for such little expense...
Good on you and have fun!
Also, since you have a dob, why don't you try and bartelise it...... you'll see heaps of ways to do it from Mel's site then you'll be imaging with it as well ! Just a thought!
Cheers
Rich
