Anthony's Astrophotography

Ok so last time I posted about the EQ8 and my first thoughts I mentioned there was a little free play in the Declination axis. Well now I have had a chance to give the mount a run I can indeed confirm the declination axis is loose “in places” and will likely need to be sent back for adjustments by an authorised Sky Watcher repairer.

To explain this is difficult but here goes: If I rotate the declination axis (via the motor not the clutch) stopping every 15 – 20’ and checking for any back lash I can find a point in the rotation where backlash is very minimal (basically Nil backlash). At that point I placed some tape on the axis to identify where the tight spot was.

I then proceeded to drive the axis around a full 360’ rotation repeating the 15-20’ stops to check the backlash. What I found was the further away I got from my marked ideal point I could feel more and more backlash come in to play (up to 180’ out). As I kept rotating past the 180’ point I could feel it start to tighten up again back to the idea point.

From this I believe the declination axis to have an out of centre worm wheel (maybe by only 1mm or a fraction thereof) but out of centre nonetheless. This would mean there is no way to adjust the worm gear any closer when in the loose part of the rotation as it will start to bind at the ideal (marked point) of the rotation.

Why is this an issue? What this translates into in the real world is it can literally take up to 2 seconds to engage the gears when driving between North and South directions. For example when I perform a “goto” to a part of the sky where the gap between the gear meshing is at its worse, the scope can physically be moved (rocked) back and forth. However my biggest issue with this is when imaging and guiding the rate of adjustments sent to the mount are so small that it can take up to 10 seconds to actually start driving the gear in a direction and by that time it is too late as the Sub exposure is ruined.

My work around for the moment and how I managed to get the image in this post is to have the polar alignment slightly off so the mount is only driving in one direction in Declination. However this to me this is not really a suitable solution.

I have contacted Tasco Australia’s service department and have been advised by them to check my set up process and follow the manual as written by Sky Watcher (which I have done), I have also been asked to perform a Motor Controller firmware update to version 2.09.04 (the mount was actually shipped with this version so no update was needed, I did however update the SynScan Hand controller). After following these instructions the problem still exists.

At this stage I have advised Tasco that there has been no change and am awaiting the next steps from them to advise what needs to be done. At this stage I am okay with the fact there “may” be a problem with the mount as sometime things just happen. What I will be interested to see is how Tasco and Sky Watcher handle my query moving forward and what their resonce is to the proposed fault as I see it? After all this is not a small investment in a mount.

Let’s see what happens and I will post more details as they come to light.

Cheers

Anthony

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