Help with lakeside autofocuser and esprit 100

[5haan_A]

Hi,

 

Has anyone had any issues with a lakeside auto focuser attached to an esprit 100?

 

I am controlling the auto focus unit with APT and essentially what I am finding is: the the position it shows that the focuser is at means jack diddly. Every session the focus is at a new point sometimes 150 steps away even if I have the same Temperature. What I have inferred from my testing is that the focuser seems to go more in one direction than the other if you know what I mean. Basically that a step in is not the same as a step out. 

What this means is that it takes me forever sometimes an hour just to get my focus right, which is quite funny because the lakeside auto focuser was supposed to save me time. I use a bahtinov mask as well whilst focusing and use the bahtinov aid on APT to help me get there.

 

Has anyone resolved similar problems and how do you speed up focusing with an auto focuser.

 

Best,

[Laurin Dave]

Have you got the backlash set high enough,  not sure how to do that in APT

[symmetal]

Check the Lakeside motor unit is firmly attached to the focuser shaft. A grub screw can work loose causing severe backlash. There should be no movement when trying to lightly move the coarse focus knob on the other end of the focuser shaft and a small amount of movement (around 5-10 degrees) when the fine focus knob is gently moved.

To check the amount of focus backlash compensation needed to be set in APT, it can be checked by commanding the focuser to move out and then in by say 20 steps. If you see the fine focus knob rotate a little after the focus in command then your backlash is overcome by the 20 steps. If it doesn't move increase the distance you move in and out each time until it does show inwards movement of the fine focus knob. This is the distance you need to set in APT for the backlash value. I assume there is an option in APT to force compensation in one direction only (normally inwards) so that the autofocuser always finishes movement in an inwards direction. This way it ensures the teeth are fully engaged driving the focuser in an upwards direction, (against gravity). There's no problem with setting the compensation too high, it just means it takes a bit longer to do the compensation as it has to travel a bit further each time. I use SGP but assume APT has similar backlash settings. 

You can set backlash compensation in the Lakeside Astro driver but it's easiest to let APT do it as it's quicker to change the value. The focuser current position is stored in the Lakeside Astro controller so after turning it all off and back on it knows the focuser position, (assuming you don't move the focuser while it's turned off.

Alan

Edited November 28, 2019 by symmetal

[Davey-T]

You can use the Lakeside utility to make sure it's not just an APT problem.

Dave

[5haan_A]

On 28/11/2019 at 19:52, symmetal said:

Check the Lakeside motor unit is firmly attached to the focuser shaft. A grub screw can work loose causing severe backlash. There should be no movement when trying to lightly move the coarse focus knob on the other end of the focuser shaft and a small amount of movement (around 5-10 degrees) when the fine focus knob is gently moved.

Cheers Alan. It was the grub srews. I took apart the whole focuser down to the gears. Put it all back together with the right level of tightness. Now the coarse knob doesnt move at all, which before taking it apart it did. 

 

Thanks for the help. 

[symmetal]

12 hours ago, 5haan_A said:

Cheers Alan. It was the grub srews. I took apart the whole focuser down to the gears. Put it all back together with the right level of tightness. Now the coarse knob doesnt move at all, which before taking it apart it did. 

Glad that's all it was.   I had my grub screw work loose which caused a similar problem. You need to ensure the grub screw is tightening on the flat section of the focus shaft. As you tighten the grub screw wiggle the coarse focus knob on the other end to ensure it's sitting in the middle of the flat section.

Alan