View Full Version here: : Robofocus and two telescopes
22-05-2012, 06:37 AM
Can anyone shed some light on using Robofocus with two telescopes.
I am using it successfully on one telescope (with focusmax) and would like to use the same controller and another telescope with its own stepper motor.
A few questions:
Do I have to reprogram the controller each time I switch between the scopes to the inner and outer limits of travel?
Is there a way I can store those settings in the software on the computer?
How does the controller "remember" where each stepper motor was when switching between scopes? Do you need to follow a particular procedure, e.g. always return the focuser to fully in??
Thanks in advance,
22-05-2012, 11:24 AM
The RoboFocus steppers don't have absolute position encoders inside them or any sort of external position indicating feedback mechanism.
So they never know exactly where they are automatically !
You need to send them in one direction until they hit a physical stop (eg start of focusser travel), the motors are continually stepped for a longer period and since they simply stall no damage is done.
Afterwhich this position is then determined to be "Home"
From that point on the Robofocus Controller keeps an accurate count of every step or microstep that it sends to the motor so it 'thinks' it knows where it is.
I say 'thinks' it knows because if the motor load is sufficiently high - eg lots of weight, focus lock turned on, or the focusser movement is jammed or it hits something, it will merrily step the motor and not realise that its not moving and then everything will be out.
So really you will have to "home" the device every time if you want a reliable position.
While you can send it home each time you finish, this doesnt allow for any movement as a result of disassembly and power outage situations.
Fortunately the Robofocus software understands this very well so it defaults to automatically calibrate the home position each time you start up. Just make sure this calibration moevment is oart of your startup software's process and it wont take long
In some ways its preferable anyway - trying to reliably get back to a position in the microns range on an OTA that is potentially assembled and reassembled each night is difficult at the best of times, so verifying each time is good.
Think of it more like 'Home' being a physical positioning process as apart from a software setting.
Hope that helps
23-05-2012, 08:33 PM
Do you just select the different profile in the software and plug in the next focuser?
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