trying to configure steps accurately, need some advice


skyguynca
 

Is there a way to tell onstep to give me x number of steps?
I am trying to configure my steppers and worm gear box. it is an 80:1
When i put the info in the configure spreadsheet and then inter it into the config generator
what i get isn't right. I put in a target that should be less than 360 degrees on the axis,what I get as output
is 5 or 6 full 360 degree rotations on the gearbox.

If I can give specific x number of step commands then I can adjust the rotation degrees to suit.

Thanks
David Mikesell
San Jose, CA


 

David,

You provide 4 parameters into Khalid's spreadsheet to calculate the total number of microsteps per degree for each axis, used in the Config file.

1) Motor type - 200 or 400 step
2) Microsteps used in the driver while guiding - 8, 16, 32, 64?
3) GR1 - Your first gear reduction ratio if using pulleys.  This is: (# of teeth on worm pulley) / (# of teeth on motor pulley).  Usually this is somewhere between 3-5.
4) GR2 - The number of teeth on your axis gear.  You seem to indicate it is 80

The spreadsheet multiplies the above four values and divides by 360, for each axis.


George Cushing
 

David, not sure what you are trying to do here, but the spreadsheet's calculations are based on the assumption that you will need more than one full motor rotation for any movement of your mount. If you are trying to limit slews to avoid crashes there are provisions in OnStep for software controlled and hardware controlled slewing limits. 


skyguynca
 

Did that, in my post I even said that. It is still not working out correctly


skyguynca
 

I used the calculation spreadsheet I use the configuration program. I am not trying to limit my slews because of crashing. My stepper to gearbox is 1 to 1 my gearbox is 80 to 1. Yes all that is entered into the program but it is giving what should be 80 Revolutions of the stepper per degree 300 + rotations which is wrong. I need it to where it only gives 80 Evolutions / 360° of the gearbox.

That is why I am asking if x number of step commands can be sent to accurate set steps per degree.

David Mikesell
San Jose, CA


skyguynca
 

Oops, mistyped " but it is giving what should be 80 Revolutions of the stepper per degree 300 + rotations which is wrong.". What it should say is instead of giving me 360 degrees per 80 motor 360 degrees of rotation on the stepper I am getting around 1040 degrees.

David Mikesell
San Jose, CA


kevin
 

Can you please explain what your setup is i.e is it a 200 step motor with a 80:1 gearbox direct drive ( no worm) on  each axis?
what microstepping and what driver are you using?
Can you attach your config.h file
 n = (stepper_steps * micro_steps * overall_gear_reduction)/360.0  steps per degree of OTA movement
eg. 200step motor * 16 microsteps  * 80 gear box    divided by 360 =  711.11 pulses per degree if you want you could just enter that into config.h
#define AXIS1_STEPS_PER_DEGREE   Change number if different microstepping.


skyguynca
 

200 steps, 32 microsteps, 1 to o e stepper to gearbox and gearbox is a wormgear box at 80 Revolutions input to 1 revolution output.


 

Since you have no reduction from motor to gearbox/worm, the entries should be:

200 (for stepper)
32 (for microsteps)
1 (for GR1)
80 (for GR2)

The Axis Steps per degree will be 200*32*1*80/360 = 1422.222


 

Like this...bold are your entries.

          Axis1 is for Right Ascension or Azimuth        
          Axis2 is for Declination or Altitude   AXIS1_DRIVER_                 Gear Reduction
    Stepper-Steps MICROSTEPS GR1 (Other stages) GR2 (Final stage)
AXIS1_STEPS_PER_DEGREE 1422.22222 200 32 1 80
AXIS2_STEPS_PER_DEGREE 1422.22222 200 32 1 80


skyguynca
 

Ok, after playing around in the config.h I got it figured out. Thanks Kevin for the info. Since decimals aren't allowed in steps per degree, what area in onstep do you go to to put correction data to make tracking more accurate for astrophotography?

Thans for the help

David Mikesell
San Jose, CA


skyguynca
 

Thanks Otto, got it done already playing in config.h file. Now looking how to compensate and error correction for tracking

David Mikesell
San Jose, CA 


kevin
 

On Fri, Jan 21, 2022 at 07:15 PM, skyguynca wrote:
Since decimals aren't allowed in steps per degree,
i think they are and whole values  should end in .0 so it knows they are not integers and are treated correctly.


 

David,

You mean PEC, or Periodic Error Correction?  I am familiar with the concept but don't use it.  Maybe someone else can chime in.

Putting PEC aside for a moment, the best thing to do is Guide with a guidescope, guide camera and the freeware called PHD2.  It is really a phenomenal setup.

For my set-up, I use an 50mm SVBONY guide scope ($60 or $70?) with190mm focal length, and a ZWO ASI120MM Min ($150).  When you load the ASCOM drivers for OnStep, PHD2 will connect to the camera, guide on a star and send RA/DEC correction signals to Onstep which will then tell the motors to move according to the guiding instructions.  You can also use PHD2 to polar align your mount (assuming you can polar align it).


George Cushing
 

Before you start playing with PEC you have to improve your tracking resolution. Your current setup is estimated to give you a tracking resolution of 5.23 arc-sec/sec. For AP that should be 1.25 arc-sec/sec or less. The Vixen Great Polaris SkySensor with a 2304 steps per arc-degree (1.95 arc-sec/sec tracking) was not good for even visual use at higher magnifications, the step pulses could be seen.

To get AP suitable tracking resolution you will need to interpose an 8:1 reduction at GR1 or GR2, if you 80:1 gear reduction is connected directly to the motor. Just going to a 400 step motor only gets you into the Great Polaris category.

2304.00000 48 1 120 144


skyguynca
 

Thanks for the info George