Focuser issue

[Rick Spencer]

I have a SW Explorer 200pds with the dual speed focuser. I have just added a SW auto focuser and I noticed that it slows down and sometimes stops, possibly around the same point in the focuser travel (?). With a little nudge, the auto focuser will continue. Is this an issue with the auto focuser or a slight "tight spot" in the drawtube? How can I remedy this, without destroying anything? I have noticed that the tube has two parallel wear lines on the outside edges of the flat area.

[Peter Drew]

I think it is more likely a "tight" spot on the focuser travel. Disengage the auto unit and see if you can feel any variation in resistance focusing manually. The wear marks on the drawtube seem to be normal.   ?

[RolandKol]

1 hour ago, Rick Spencer said:

I have a SW Explorer 200pds with the dual speed focuser. I have just added a SW auto focuser and I noticed that it slows down and sometimes stops, possibly around the same point in the focuser travel (?). With a little nudge, the auto focuser will continue. Is this an issue with the auto focuser or a slight "tight spot" in the drawtube? How can I remedy this, without destroying anything? I have noticed that the tube has two parallel wear lines on the outside edges of the flat area.

The wear marks are from two rollers which hold the focuser's tube in line inside the focuser,  you can clearly see them from inside of the OTA, - it is completely normal.

It is quite odd you have such a problem as I cannot foresee any mechanical obstacles to cause it... unless the motor is a bit too weak to move all the rig you have... Maybe if you would specify your autofocuser and the rig you use, - someone would be able to advice...
By the way, - Is your focuser's tube shortened? if so, - there is a very low possibility you retract focuser OUT too much and when it goes IN, - tube catches these rollers which leave marks on the tube, - this probability is close to "miracle", as I doubt your motor would be able to move focuser IN once the tube has slipped off the rollers...

P.S. haven't you tried to check what  is actually going on inside during a daylight? if the tube was shortened and it falls from rollers, - you will see it... however, the slight nudge probably would not be enough to place the tube back.

P.P.S. how is your camera positioned on the scope? at 12 o'clokc or at 6? 

if it is at 6, - do not loosen your focuser tightening bolts.... camera, together with the whole focuser's tube, may slip out....

[Rick Spencer]

 

 

17 hours ago, RolandKol said:

By the way, - Is your focuser's tube shortened? if so, - there is a very low possibility you retract focuser OUT too much and when it goes IN, - tube catches these rollers which leave marks on the tube, - this probability is close to "miracle", as I doubt your motor would be able to move focuser IN once the tube has slipped off the rollers...

P.S. haven't you tried to check what  is actually going on inside during a daylight? if the tube was shortened and it falls from rollers, - you will see it... however, the slight nudge probably would not be enough to place the tube back.

P.P.S. how is your camera positioned on the scope? at 12 o'clokc or at 6? 

if it is at 6, - do not loosen your focuser tightening bolts.... camera, together with the whole focuser's tube, may slip out....

Apart from the addition of the Skywatcher Auto Focuser, the focuser itself is as stock, it has not been modified or shortened in any way.

I have not even tried it with anything in the focuser yet, this happens without any eye pieces, cameras or anything else inserted into the tube.

[RolandKol]

Try to turn focuser manually without a motor... you will feel if it jams somewhere..

and do opposite, - turn on the motor without focuser and check how it rotates (add something on the shaft to make it easier to see it spin, - sticknote or plaster, anything you have by hand).

if motor does not rotate seamlessly, - change batteries, check cable, re-check how it spins.. if it is the same, -  return it back to supplier...

if both, focuser and the motor are OK... No idea... maybe power supply was not reliable (batteries or cable)...