owners of gso crayfords! what are the focus knobs made of?

[elusiver]

just wondering what the focus knobs on the gso crayford are made of.. and if they're detachable.

do they attach the same way the r&p knobs attach? and will the plastic knob of the r&p attach to the crayford?

at the moment i'm working on an electronic focuser for the dob.. but just wanna see if i upgrade to the crayford down the track the focuser will be easy to port accross.

el

[slice of heaven]

Their aluminium and they seem to be removable. Theres a allen screw,which I presume is locking it to the shaft. Maybe Rob..rmcbp.. can try swapping knobs as he has both.

[rmcpb (Rob)]

I will have a play tomorrow and get back to you on that one.

[elusiver]

thanks rob.

el

[Dave47tuc (David)]

There aluminium and are removable

[rmcpb (Rob)]

They are aluminium with a rubber insert around the knob. They have a smaller diameter than the R&P knobs and attach differently so, I would not try interchanging them.

How are you going to attach the drive? If its a belt drive it should be fairly interchangeable.

[elusiver]

it's based on this:

http://www.wideopenwest.com/~mgray8351/Focuser.htm

but i'm using a different stepping motor circuit.. so at the moment i'm writing up the application to control the motor in VB. Didn't want to use a belt drive as they look abit more fiddly than using gears. And didn't want to use a servo/dc motor as I wanted something that I can computer control.. not that i'm doing any imaging.. i just thought it'd be cool

thanks for the info rob. Looks like i won't be using epoxy but make a hard attachment of the gearing so that I can switch it accross to the crayford when i get it.

el

[rmcpb (Rob)]

Hmmmm.

Couldn't you just use a friction drive on a rubber covering on the focus knob? It should work OK and give you the advantage of being able to disengage it easily by pulling the spring loaded motor away from the focuser on a slide. This would be interchangable with the Crayford when you get it by just changing the speed of the stepper motor.

You are lucky to be able to understand stepper motors. That is one of the reasons I have not got back to my equatorial platform, the lack of fine control.

[davidpretorius]

elusiver,

please let me know how you go with this as i am going to get the 12" dob with crayford and want to control with stepper motors etc thru my lappie and .net (VB)

[elusiver]

well that's the catch rob.. i don't know anything about steppers!!! or much about vb really.. but i'm getting there!!! i got a jaycar stepping kit.. so that part was easy.. and I'm making the control application in VB6, not .net.. as i'm having enough trouble as it is with vb6 which i'm the tiniest bit familiar with i'd have no hope with .net. The stepping kit from jaycar comes with a very basic control application(it just has 2 buttons for spin clockwise and spin anticlockwise).. so i'm re-writing it to include single step in either direction, speed control and presets.. I did about a semester of IT at tafe 6 years ago now.. so I'm TRYING to remeber what little i learnt in that.. I've got pretty much everything sorted now.. just gotto make the mount and fine tune the control application. Finished off the electronics of the hand controller tonight(simple move in/out with a speed controller) so I've just gotto find a housing to put it into. The good thing about the stepper is that it shouldn't need to be disengaged becasue it spins freely with no power through it i'd say its still a couple of weeks away realisticly.. cause i'm only working on it here and there.. and the project has to compete with an obsession with GTA san andreas i've got at the moment

el