HyperStar focus travel is quite a ways away from the native focus on a C9.25. I cannot speak for the C8's but I imagine it is quite large as well. So using my ZWO EAF at the factory default limited 60,000 steps wasn't enough to swap back and forth. With experimentation I found I needed approximately 85,500 steps. I searched and found nothing in writing to expand the 60,000 limit to 95,000. So I experimented and found the following way to expand the step limit:
1) I found HS focus manually I then set the EAF to 500 and then tightened the allen screws on the motor axle (HS focus is now perfect at 500 steps - 500 not zero for wiggle room).
2) I then set the step advance to the 60,000 position.
3) In SharpCap I then click on setup.
4) In the ZWO ASCOM properties/control box I clicked on advanced and entered 95,000 in the Maximum Step Size box (I do not know if you can push this past 99,999).
5) Using the ZWO controls (not SharpCap) I then advanced the focus until I found it at 85,500.
I was watching SharpCap mimic everything I was doing in the ZWO control window - excellent.
6) I then closed the ZWO properties/control and tried adjusting focus using SharpCap. SharpCap immediately started heading down to the 60,000 position. I quickly learned you have to restart SharpCap to get it recognize the new 95,500 limit. However with one restart I was good to go with my new focus limit.
I am so pleased that my ZWO EAF can now handle my EAA HyperStar focus limit on one extreme and my native focal length for planets on the other extreme end.
I am pretty sure ZWO put in the limits it did to prevent over focus travel damage liability.
Anyway this is one more way to enjoy EAA while quickly setting focus close enough to get started, as star party attendees are looking over your shoulder.
Bust Through the ZWO EAF 60K Step Limit
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kaymann
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Bust Through the ZWO EAF 60K Step Limit
Last edited by kaymann on Wed Nov 15, 2023 3:59 pm, edited 1 time in total.
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Re: Bust Through the ZWO EAF 60K Step Limit
Hi,
glad to hear that you got it sorted. As you found out, SharpCap only asks for the maximum position of the focuser when it is first selected, so changing the maximum is not picked up. A stop/restart of SharpCap will certainly fix it, you could probably fix with a disconnect/reconnect or changing the hardware settings to a different focuser and then back again.
Many focuser setups with an EAF might have a range of only 10 or 20 thousand steps, since with a refractor or reflector focuser the whole range is just a few turns of the focus knob. I have hit the end of range many times with no damage (either the stepper motor will stall or there will be a clutch somewhere in the focus motor drive train that slips).
An SCT is different as the focus range is dozens of turns of the knob, forcing you to make the adjustment to the max range. Hopefully this is something that you only have to do once and that the EAF should then remember the change.
cheers,
Robin
glad to hear that you got it sorted. As you found out, SharpCap only asks for the maximum position of the focuser when it is first selected, so changing the maximum is not picked up. A stop/restart of SharpCap will certainly fix it, you could probably fix with a disconnect/reconnect or changing the hardware settings to a different focuser and then back again.
Many focuser setups with an EAF might have a range of only 10 or 20 thousand steps, since with a refractor or reflector focuser the whole range is just a few turns of the focus knob. I have hit the end of range many times with no damage (either the stepper motor will stall or there will be a clutch somewhere in the focus motor drive train that slips).
An SCT is different as the focus range is dozens of turns of the knob, forcing you to make the adjustment to the max range. Hopefully this is something that you only have to do once and that the EAF should then remember the change.
cheers,
Robin