Re: Onstep Goto Accuracy


Hemendra Rawat
 

Hi Khalid,

The RA and DEC axis move smoothly without the 8 inch OTA. When I put
on the 8 inch scope, the RA axis slow motion knob becomes a bit stiff
but I never expected the stepper motor would lose steps. What are the
benefits of increasing the motor current to 60% ? Will it improve the
torque? Also, do you think reducing the micro-steps from 32 to 16 will
help? I have a 8x40mm finderscope on my scope. So, even if the Onstep
goto can bring the object in the FOV of the finderscope, I should be
able to center it in the FOV of the scope.

Regards,
Hemendra

On Thu, Jul 15, 2021 at 11:39 AM Khalid Baheyeldin <kbahey@gmail.com> wrote:

First, is the mount smooth enough with nothing on it? If you disengage the clutch and push it gently with one finger, does it move smoothly? If it does, then lubrication is unlikely to be the issue. If it is not smooth, then the motors may be fighting to move them adequately, and that mechanical issue should be rectified before you try anything else.

Second, you say your LV8279 are at Vref 0.557V, but there are two versions of them that have different resistors, as explained in this message. For your motors, the starting current to try is 0.9 X 1.41 X 0.4 = 507mA. You can also try 0.5 (50%) instead of 0.4 (40%), so 635mA, and see if there is any difference between the two.

Third, there is a point at which one has to live with the mechanical capabilities of a given mount (i.e. not exceed the practical capacity limit, which may not be the advertised limit, but significantly less). To get over this, one may need to upgrade to a larger, often more expensive and more precise, mount.

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