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Hello,

I am in the process of automating my focusing by adding a Lakeside focuser to my FSQ85. I have an Avalon Linear mount which has two Aux connectors which can be used to control stepper motors. However in the manual it has a note that once an adjustment is made he Avalon StarGo controller will cut the power to the stepper motor until the next adjustment happens. So my question is, in between focusing where the stepper motor has no power will the motor hold the focus in place even if there is some slippage in the Tak focuser? I.e. is there a lock mechanism which stops the motor from turning if no power is applied? Or are there other focus controller which hold the focus in place all the time?

Thanks,

Mike

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Hi Mike

The focuser is driven through a gearbox from the stepper. This is a very effective mechanical brake.

However, the Lakeside drives the stepper directly from it's own controller, there's no need to go via the mount.

Regards

Andrew

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  • 1 month later...

Thanks Andrew. I was hoping to use the Linear's AUX controller to save some cost as the controller seems to be the expensive part of the focuser. However it looks like this won't be possible in any case as the Linear is not compatible with the Lakeside motor.

Mike

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I have just added a Lakeside to my FSQ85.  Without power to drive the stepper motor it is very difficult to turn, you can only do so with force.  So I don't think your focuser will be slipping, trust me.

I will be interested in how many steps you get when you calibrate your Lakeside to the FSQ.  I get 1650 fully in to fully out.  I also get quite a bit of backlash, takes 15 steps to take out the backlash when changing direction.  With the Lakeside on my Feathertouch focuser on my TEC 140 it only takes 3 steps to take out the backlash.

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Mine goes from 0 (not quite fully in) to 7800 so your value sounds way too low. I've never measured backlash as I've never noticed it as an issue.

Check that your focuser has enough tension in it by putting the scope on a bench with the focuser racked out, hold the scope firm with one hand and press down on the back of the focuser with the other. There shouldn't be any play.

Andrew

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Thanks.  The focuser of the FSQ itself is fine and racks all the way in to all the way out without an issues.  How come you have so many more steps (and hence focus granularity) than me? I used the Lakeside calibration routine so why is mine so different from yours?  What is your step size set to in the Lakeside utility or on the handset?

In actual fact, on my TEC 140 - that I also have a Lakeside attached - from almost in to all the way out I have 4000 steps - for almost four inches of travel.

 

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You can work out steps roughly and then experiment using something like Focusmax you can see how much the HFD changes between autofocus steps, I forget how much they recommend but all the info is available, no point having teeny steps, they're measured in microns so you need a few microns in one step to get any appreciable movement.

Dave

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Well my experience on my TEC - with about 4000 steps for the whole travel of the focuser, a move of five steps is enough to throw the focus out and the movement of the focuser in or out is completely unnoticeable. 

My step size is set to five so I assume that if I were to set the step size to 1 then I'd have 20000 steps or so (i.e. 5 x 4000 [current number]).  That sounds semantically more logical for a large end-to-end focuser movement but, in actual fact, does it matter?  If I have 4000 steps for 4 inches of movement, that's 1000 steps per inch, or the focuser moves 1/1000 of an inch for one step.  So in my case above it moves 5/1000 of an inch to throw the focus out.  So my level fo "granualrity" of 4000 is actually fine.....???  That make sense?

However, to counter that argument somewhat, the majority of those 4000 steps are completely "wasted" since they are nowhere near my critical focus zone of between about positions 3400 - 3600 of that range.  It would be better if I could "zoom" those 4000 steps in that critical foccus zone?  But again, does it matter?

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  • 5 months later...

Hi there,

bumping this thread as I'm struggling with autofocus and to also feed in some info for my FSQ85/Lakeside combo. I've fitted the Lakeside and I'm now trying to get autofocusing working under MaxImDL using its native routine (i.e. not FocusMax).

At a focal ratio of f5.3 I've worked out a step size of 5.8um / per step. Does this seem about right?

I select a 4th mag star and manually focus using a mask to give it a good start. MaxImDL will then create a V-curve but then go completely out of focus with the image noise giving a HFD of zero. At this point it usually jumps to a point on the curve that clearly isn't in focus.

Looking for any advice on how to get this working:bino2:

Regards, Andy 

 

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Hi Andy I use the Maxim autofocus routine with the Lakeside focuser, check the log readout the HFD should alter by about 1.5 between exposures , check your star isn't too bright if it maxes out at 64000 reduce exposure time.

How did you work out the step size ?

I think the Maxim focus routine is the same as FocusMax3 but I couldn't get that to work at all.

I have had it run away past focus and get lost at times and come up with strange messages like " can't go to 2 million steps or some such :)

Dave

 

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Hi Dave, thanks for the feedback and advice.

I calculated the step size by moving the focuser through it full range, measured the physical distance of travel and divided this by the delta change in position on the Lakeside controller.

I'll check that the star doesn't saturate as you suggest.

Thanks, Andy

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