Very annoying!

[blink138]

hello members i hope someone can help
i have a TS optics 3 inch motorised focusser on my APM 107
twice now i have set it all up ready for the imaging night, and bugger me my focusser stops at a set point when moving in, and of course is just out of focus
racking it out further then in once more does not help, it stops at the same point
after that i benched the scope, removed the motor mechanism and then manually racked it all the way in, reconnected the motor and it was fine, but on setting everything up from scratch yesterday (tripod and all!) found that i could not reach the buggery focus again................ the engine just stops at a point and no amount of racking out then in fixes it!
pat

[kens]

Is there something obstructing its movement? e.g. I had a problem with mine when the OAG screw caught the focuser housing.

[blink138]

nah no unfortunately ken / when i disconnect the motor it racks both ways fine, and when i re attach the motor it seems to rack in and out fine for that session
pat

[I.C.D]

Hi Pat it sounds like one of motorised gear may not be align or loose on the shaft can you check that .
Ian

[baileys2611]

Are you using software to move the focuser or a hand controller?

[blink138]

hmmm maybe ian, the allen screws are deffo tight, but they still need to be "aligned" properly?
still don't know why it stops in exactly the same position no matter how far racked.......... almost like a memory for it?
pat

[blink138]

hand controller simon
pat

[brian nordstrom]

Sounds like the motor focus has a stop built in ? , try setting it , say all the way in then rack the focuser in and fit the motor focuser on keeping the focuser in .
Brian.

[blink138]

if i think what you are saying brian, i have tried that
i loosened the motor, manually racked it in and then re attached the motor but it still stopped
i hope that is what you meant mate?
pat

[baileys2611]

I have an idea about losening the motor shaft from the assembly, then moving the motor without the focuser attached to see if it's a motor issue or if it's a mechanical thing inside the focuser.

Might be a longshot and it will depend on the model. Can you post a picture of the focuser and hand controller?

[brian nordstrom]

:thumbsup: Spot on what I was thinking , just something. , I presume that the focuser has no tight areas. ? All the motor focusers I have seen are not very torquey , it might just be a tiny amount that stalls ot ? .
Brian.

[joelshort]

What motor are you using, and are you using a hand controller or software to move the focuser motor?

If you are using software, the driver might be stopping the motor once it "thinks" the step count is at 0. Let's say your full focuser travel is 20,000 steps of the motor. So if fully racked in the count is 0 and fully racked out the count is 20,000.

Now, let's say if your focuser is racked all the way OUT the motor thinks it is at 10,000 steps, so when you bring it in, once the software reaches 0 it will stop.

Just a thought as this has happened to me. It's irrelevant if you are using a hand controller.

[baileys2611]

Unless the motor has an in-built stop at a point and the focuser is not attached at that point.

PAt, you mentioned you un-rack and it moves out, then in and stops at the same point? I'm wondering if you un-rack the focuser, them move it all the way in and re-rack it, then use the handset to move the focuser out and back in again will that fix it?

I'm thinking that if the motor thinks the point at which it stops is 0, then manually move the focuser so that it is at 0, re-attach the motor and maybe that will fix it.

[blink138]

hmmm i think you guys may be on the right track here

[blink138]

brian when i was racking it in manually, i would not exactly call it a tight spot, but not smooth all the way?

[blink138]

this is possible too ian, but it stops at exactly in the same spot so i cannot explain that.......... if the allen screw was not in it's notch it would slip constantly?

[blink138]

thanks joel it is a hand controller, but simons comment could make that point still valid

[blink138]

so simon this seems the most plausible................ so if i use the hand controller to rack it in til it stops automatically (this is then zero as far as the engine is concerned?) disconnect the motor, manually rack the focusser all the way in, re attach the motor and then rack it all the way out?
pat

[baileys2611]

Yep, then see if it stops in the same place again. If it works then there's a hard coded stop in the motor somewhere. If it gets stuck in the same place then...well...cross that bridge if it comes.

Let us know how it goes?

[blink138]

yep i think it has a coded stop, makes sense simon, and as i think joel pointed out once it has gone through it's 10 thousand steps it just stops
ta mate, i will try it tonight or on the weekend
pat

[blink138]

it does not have a fast speed so it is painfully slow (but wonderful) to look at haha!
pat

[baileys2611]

:thumbsup: