LFEP - tracking issues with low gear ratio?

[Armando]

Hi @all,

a few time ago I upgraded my old (black) EQ6 mount to make use of Skyscan/Synscan motors in place of the old ones to achieve higher GoTo speeds.
I just tested it and unfortunately I found an unexpected tracking error at high frequencies: about 2s pulse length with an amplitude of about 3 asec (a sort of sine rectified wave error  )
I've a 180T worm wheel, 47/12 gear ratio and 1.8° step angle.
I had no issues on the same mount with 100:1 gear ratio and 7.5° step angle.
Could the issue be related to the transfer gear's module different from the one on the worm?
Did someone else find tracking issues by using LFEP with low gear ratio?

Thank you and CS
Armando

[Armando]

I'm thinking about the pressure angle of the gear on the worm: maybe it's different from the one of the transfer gear.
The RA worm has 47 teeth and makes a revolution in 480s. So about 10s/tooth.
Maybe I'm saying a nonsense, but if the main effect of a different pressure angle is 1 acceleration, 1 deceleration, 1 acceleration and finally 1 deceleration on each tooth, I think this could be the reason of the issue... 

CS
Armando

[Antoon]

Hi Armando,

Last year we had a similar problem in ACG astrolab. (public observatory)
We connected a 1.8° stepper directly to the 272 tooth wormgear of a ALT7 mount.
We did this to achieve higher slew speeds.
The two telescopes (Lunt and TMB) were mounted on a double dovetail (losmandy)
When we looked at an object we had a slight vibration. It was a sort of resonance frequenty in the whole set up.
This is been solved with an extra gearbox of 5:1 between motor and worm.
Of course the slew speed was much lower then 
Now the problem is solved definitely. ACG bought an astrophysics "El Capitan" mount.
(I wish i had one like that  )
 

[Armando]

Hi Antoon,

by giving a look at the transfer gear of the SkyScan motor I think its tooth profile is different from the one of the output gear of the old EQ6 motors. 
I think there is no way to search for an EQ6 replacement gear to be mounted on the worm.

So I'm going to use temporarily on my EQ6 the old solution (by Conrad 100:1 reduction): max slewing speed is really annoying (40x) but tracking works as expected.
In the meantime I'll search for a 5:1 reduction by belt/pulley in place of the 3.917:1 of the SkyScan solution: I mean to give the Skyscan motors another try without the Skyscan transfer gears. Maybe tracking issues will be solved thanks to the belt/pulley and, in this case, I'll start using also PEC thanks to the integer reduction...

3.917:1 reduction didn't limit slewing speed on my mount. Maybe 5:1 reduction with the same motors and V40 won't limit it too... In the worst case 420x speed will surely be possible...
I'm only annoyed by the time I'm wasting on my cheap and old mount.

CS
Armando

[gpaolo]

Hi, I'm using the LFEP on a G11 with a 1:4 gear ratio and Astromeccanica motors. I wasn't able to put the telescope and check it yet, but the belt movement does not look very smooth. I hope to be able to mount everything in a couple of days and I will tell you if it is only a sensation or a real issue.

[the_lizardking]

For small gear ratios you should activate the sboost option in ASCOM,... then it should run smoother normaly. However there is a small issue with tracking so far which normaly does not affect visual and it can be guided out very easy.

[gpaolo]

The sboost option is the tick-box in the motor configuration?
I need the mount for photography, if it is not smooth... it is a HUGE problem.