Setting Up Scope.exe and initializing
(It wasn’t all that hard ;)
#1 Figuring out The gear ratio and the resulting arc
seconds per full step.
Since my gears were home made, I wasn’t certain of the exact number of teeth on each gear. Amazingly although each gear is the same size, one gear has a few more teeth than the other.
To figure out how many teeth each gear had, I rigged the gear to free wheel about its axis, then attached the drive motor to it. With a Laser pointer duct taped to the gear wheel and the laser spot marked, I took a guess that my gear had about 690 teeth on it (11.75” diameter = 34.52” circumference * 20 teeth per inch = 690 teeth) Next I fired up Scope.exe, went to Move/HalfSteps and command scope to move 276,000 half steps. (690 teeth * 400 half steps per 1 revolution of the 200 step stepper motor) This should have spun the gear 1 full rotation, however I cam up short. Using 400 half step moves (1 Full rotation of the stepper motor), I kept doing that until the laser came to rest at its starting position. The result was 286,400 half steps for 1 revolution of the Az gear. I repeated this several times, watching in fascination as the laser kept coming to a stop at the same point on the wall (It was really very entertaining!)
Now I know the Az gear requires 286,400 half steps for one 360 degree rotation (286,400 / 400 = 716:1 reduction). Since 360 degrees = 1,296,000 arcseconds (360 * 60’ * 60” = 1,296,000) and it takes 143,200 full steps (286,400 half steps / 2) to do this, my AzFullStepSizeArcsec = 9.050279
Next I repeated the whole process for the Alt drive, which turned out to be 714:1 reduction!
#2 Figuring out the Half Step slew speed variables
With the scope assembled, I went to Motors/HsParms and
started playing! First I played with
MaxDelay, which controls the starting speed of any slew. I found that if the slew started to fast, it
caused the scope to bounce around at the beginning of the slew. If I started to slow, it took forever to
ramp up. I ended up selecting a happy
medium between the two.
Next
I played with Mindelay and HsRampx, which controls the Top speed of the slews
on both axis and how fast it ramps up.
The two seem to relate to each other.
To slow a ramp or max speed and you get bored waiting for the slew to
complete. To fast a ramp or max speed
and the motor may stall prematurely.
I
ended up with the following:
MaxDelay = 1500
MinDelay = 500
HsRampx = 1
#3 Playing with Micro Step Variables
On the Scope-Drive mailing list you will find a lot of
posts on playing with PWMs and QSCs and PE correction. When it was my turn to do it I decided
“Screw that!” Since the Bino-scope is a
Visual use only scope, I just kept the default 20 micro-steps and their
values. The only thing I played with
was the MsDelayX and MsPause values.
While playing with MsDalayX and MsPause, I was basically
trying to find a spot where the steppers moved as smoothly as possible. Unfortunately when I found that spot, the
resulting NOISE was ridiculous! So kept
playing until I found the values that where reasonably quit AND moved somewhat
smoothly. After much playing I found
the following values:
MsDelayX = 2
MsPause = 78
It is good to note, that even with the steppers somewhat
jerky micro steps, that once at the eyepiece there is no indication of any
problem. My next scope is going to do
Astro-photography, and then I will most assuredly need to super-tweak the PWM
values. Until then, I worry less and
observer more J
#4 It’s Time to Initialize!
First lets establish some rules: (in order of importance)
#1 Do NOT initialize on the equatorial poles!
(IE Polaris)
#2 Do NOT initialize an ATL/AZ scope with
Altitude pointing straight up!
#3 Try not to initialize to near the horizon
#4 Do try to use a high powered eyepiece,
with reticule (I Always break this rule!)
Here’s how I initialize my Bino-Scope:
#1 Select a bright star from the Bstar
database (File/Datafile/Bstars.dat)
#2 Manually Slew the scope over to the star
and roughly center it
#3 Using planetarium software, I find the
star’s Local Atl/Az coordinates (Palm Pilot App)
#4 I enter the star’s local Alt/Az into
Scope.exe (Coord/inputAltaz)
#5 I reset scope’s Alt/Az to the input data
(Reset/AltAz)
#6 Set Handpad mode to Init 1
(Handpad/SelectHPMode/C (init 1 on))
#7 Back to the eyepiece, Center the star and
hit upper left option button
#8 Select a Second bright star for the Bstar
database (File/Datafile/Bstars.dat)
#9 Set Handpad mode to Init 2
(Handpad/SelectHPMode/D (Init 2 on))
#10 Manually Slew the scope to the second
star
#11 Center the star and hit upper Left option
button
#12 Display inits to see if they seem
reasonable (Init/DisplayInits or Hotkey I)
#13 Perform an Altitude Offset
(Init/altOffset or Hotkey A)
#14 Select nearest Messier Object
(File/Datafile2/Messier.dat)
#15 Slew to object (Move/Equat or Hotkey 1)
#16 Mentally do a little ‘Happy Dance’ when
you see the object in the eyepiece J
During
observation, if any of the following happen:
#1 You drive the scope into the step
ladder and stall the motors!
#2 You lose power to the stepper
driver
#3 The motors stall during a slew
for some reason
#4 A spring flies off and a motor
disengages!
You
may either:
#1 Wish you had encoders!
#2 Kill all inits and start over
(Hotkey K)
#3 Select an object from a database,
center it, and Reset/Equat
I guess that’s it ;)
Take Care
James Lerch
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