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Old 09-10-2020, 01:38 PM
hamishbarker
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hamishbarker is offline
 
Join Date: Mar 2017
Location: Nelson, new zealand
Posts: 49
from what you are describing, assuming the slow/fast description is referring to error in the RA motion direction and not N/S (dec) it sounds to me that the centre of gravity of your telescope AND the moving part of the platform combined may be below the polar axis.


because they are below, at the beginning of motion the actual centre of gravity is going downhill to the bottom of the arc of motion around the polar axis. then they have to climb back uphill after passing the meridian.

Ideally, the CoG is located on the polar axis, then the stepper has to do just constant work against friction but is not lowering or raising the CoG.

if your telescope simply sits on the platform and the platform isn't part of its azimuth board, you may be able to try some adjustments without modifying the platform.

you could place your telescope a few cm towards the north end of the platform to bring the centre of gravity closer to the polar axis to see if that improves things.

you could also try placing the telescope towards the south of the platform, to see if this makes your tracking speed problem worse.

finally, try placing the telescope a bit to the east of the centre. then it should start with less speed error and gradually get slow as it starts to have to work uphill.

Quote:
Originally Posted by Greggles View Post
Hey every one,

Got some good testing in tonight with interesting results.

So from the start position the mount is tracking to fast, middle is tracking quite well, and towards the end it is tracking too slow. Having said that, at the middle of the platform i was able to have mars in the center of view or my asi462 with a 3x barlow, 600x600 for 10 minutes before clouds came over and swallowed Mars

Now from my understanding the stepper motors speed do not change dependent load. so i believe it is either due to the direct drive system minutely slipping or my vertical sectors are not correct.

i can rationalize the slipping as its faster when the weight of the platform is on the left of the drive shaft pushing the platform right. Where as it at is slowest when the majority of the weight of the platform is on the right hand side of the drive shaft and the motor is trying to pull up the platform with the platform wanting to fall in the opposite direction. i have no idea if i am explaining this in a way any one is going to understand!!


however i need some help determining if the vertical sector shapes could be an issue? for the life of me I cant figure out if the slow and fast speeds mentioned above could come from the sector shapes being incorrect?

Anyway, if any one knows if either of the above two things could be the issue please let me know.

Kind Regards,



Greg
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