motor focus with position readout/setting

[Robert_T]

Hi all, another equipment question. I've heard tell of motor-focus units that provide a numerical read-out (or that even got to a particular stored focus setting on command) of where you're at so that you can quickly re-focus for different colour filters etc.

Would welcome any comments on these, and whether they're only available as complete focusser units or as add-ons to existing motor-focus units?

thanks,

[[1ponders]]

Try the JMI Catalogue Rob. They have a product called the Smart focus that connects to the JMI NGF-CM motorized focuser for Cassegrain and refractors. Look under Focuser Controls. (http://www.jimsmobile.com/list_search.htm)

[rogerg]

Lots of these kind of products out there. RoboFocus by Home Dome, JMI's Smart Focus, and then there's several others I remember coming across in my searches a couple of years back.

I use RoboFocus on my JMI NGF-C. I think it used to be that the RoboFocus was a stepper motor so could accurately go to an exact step/location, where as the JMI one was a servo motor so didn't have the same level of repeatability. I could be completely wrong, it's been quite a while since I compared them, but that's something to watch out for.

I control the RoboFocus through the computer where it has all the advanced controls you'd want - go to exact position, move in/out by x amount, temperature comphensation, compatability with Ascom and hence lots of other pieces of software such as FocusMax.

I once did a bit of a write up on it, I have no idea how relevant it now is, it's been years: http://www.rogergroom.com/rogergroom/esh_rog_item.jsp?Item=65

Roger.

[Robert_T]

Thanks Paul, Roger, both great links and plenty to ponder now. :)

[Merlin66]

Thinking about the Orion DC focusser motor.... cheap and very effective only down side is being able to control via USB/Serial etc from within your favourite program.
Don't think you really need "readouts" you can use DSLRfocus etc to find the sweet spot.
With the ASCOM interface does anyone know how to pulse the DC motor remotely????