Digital, Temperature Compensated Focusser.

Hi Dave,

I think I may have misled you! What I meant is how would the motorized focuser be able to handle a CCD camera weighing at least 2 kgs and with the telescope pointing overhead.

Ah now I see, sorry your point was clear, just my misreading of it.

Yes that could be a problem. I was planning to attach the motor to the focus knob by using a drive belt. That way you don't have to make any mods to your focusser. Looking at the datasheet of the stepper controller there is a logic input, which if sen't high, syncronises the motor phases to avoid vibrations. I'll set it up so you can leave the motors energised or de-energised at your choice.

On other thing which is a problem, the IC package for the stepper controller is the a very strange zig-zag (ZIP) package and the datasheet recommends soldering direct to the board. This might rule out using stripboard for the project since the pitch of the pins is non-standard. I'm working on a PCB for this project. So when its done and tested you either print the board yourself using the supplied artwork alternatively, i'll get a small run of the boards made and supply them at cost.

Dave,

Any update on the focuser?

Thanks
Darragh

Dave, just wondering, are you an electrical engineer or something in that area, or are you just a wacky inventor genius type?
Just intereseted as ive noticed, if you hit a hurdle, rather than look to purchase a solution like most of us do, you invent something!!!

Its a terriffic trait to have, rather than look at a mountain and decide, bugger it, is it much better up there anyway, you will invent some sort of portable escalator to get yourself right to the top!

If my question is a bit intrusive/personal then please disregard it.

Dave,
Firstly, best of luck with making this. I have a Robofocus system on my telescopes so don't have much need for this Hope it works out for you.

Temperature compensated. Built in digital thermometer can report back to any software capable of dealing with it.

IMHO, I think this is a little unnecessary, especially in our climate where the temperatures are relatively stable in comparison to warmer countries. There are so many other variables to worry about when imaging. However, if you can do it easily, then fire away. However, if it takes alot of work to put in this feature, I wouldn't bother.

Uses a drive belt to drive the focus mechanism on the focuser so it will be compatible with a very wide range of focusers. You could of course connect the stepper directly to the focuser too.

I'd go with a direct connection Dave if using a scope exclusively for imaging. It climates flexure and slippage, which may occur with a belt system. Most modern focusers can easily have the focus knob removed. However, a belt connection would be handy if using a scope for both imaging and visual use as it would allow quick disconnection of the electric focuser. I wouldn't expect it to be quite as accurate as a direct connection, but might be a good compromise. As you know yourself, accurate focus is an absolute must.

Hope these suggestions help and best of luck with it.

Any update on the focuser?

Darragh,

I hope to have the prototype built this week, just working on the artwork for the PCB as I type. Watch this space.

IMHO, I think this is a little unnecessary, especially in our climate where the temperatures are relatively stable in comparison to warmer countries. There are so many other variables to worry about when imaging. However, if you can do it easily, then fire away. However, if it takes alot of work to put in this feature, I wouldn't bother.

Thanks very much for your excellent feedback Michael.

Yes I agree it's wholly un-necessary in this country, but hopefully some guys from other countries will build it and it might be needed there. It's no big chore to add a temperature sensor to the circuit. Anyone building it here can just leave it out if desired.

I'd go with a direct connection Dave if using a scope exclusively for imaging.

Yep that sounds like good advice. I'll personally be trying both ways. and of course it will be up to anyone who builds it to decide on how to attach the motor to the scope. The number of steps per-increment will be defineable as will the size of those steps. The IC is capable of full steps right down to 1/16th microsteps so it will work with a wide variety of gearing ratios.

Really I'm just diseigning and building the circuitry, the mechanics of getting it onto a particular scope will be up to the builder. I think most commercial systems work at least partly similar to this. Some provide brackets but of course it's impossible to detail every scope.

I do thing the drive belt option would work very well with SCT scopes though!