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Hi to all.
The most popular mounts - even those that are included in the small-medium range group, do drive the axes rotation via worm wheel coupling .
This one are plagued by the drawback that I have always considered very unpleasant: the mechanical play is not properly controlled and it can’t be always limited within acceptable tolerance limits.
The adjustment of Back Lash (BL) is entrusted to two screws (more often they are grains) usually positioned at 180 ° from each other. However - as we all know, even a wheel very slight eccentric creates
an inconstancy of contact with the worm: when the play is adjusted for an initial position of the axis, it is not in other positions.
In other words, there are positions where the worm rotates with adequate friction, others in which the same friction can increase significantly, and still others where it is so reduced to the point
that it causes excessive play.
So, the tuning screws are sometimes too tight and sometimes too loose … mission impossible to find the right compromise!
This behavior is already annoying in manual movement because the task of pointing at an object in a steady way is not feasible because it ever 'jumps'.
In photography it's even worse.
Not only does an unavoidable backlash often appears in Dec – and it is very badly correctable also by the autoguider software, but- and it is dirty worse, the tracking in RA does not perform evenly
and smoothly. The typical ‘micro’ irregularities in star images is what we see in our shots.
Many high range mounts adopt different methods to contain lashes, and the best ones adopt mechanical systems with which that error is reduced to zero.
With this long introduction, I will tell you what very simple modification I thought of making on my HEQ5.
Please, stay tuned 🙂
With ongoing issues related to slewing in the EQ3 pro it's quite clear that there is some significant backlash.
I understand there is a way to repair this myself; does anyone have details of guide for the EQ3 pro to reduce the backlash?
I also understand that the lubricant is important to reduce backlash. Can anyone make any recommendations here too?
I have quite severe backlash, such that guiding assistant just gives up. It seems to be about 11 secs in total, the one time GA came back with anything, but it's about 3-4 secs if I measure it by hand. Here's some guiding. Actually, it's worse when I'm dithering.
So, I tried measuring the backlash with by counting and it's about 3-4 secs. If I used PHD2 guiding assistant, mostly it fails, or it comes back with a very big number, like 11,350 msecs.
I tried entering this:
But then I got a see-saw mechanism, even when I dropped 8,000 to 3,000 it was the same.
I've taken the motor off just now and looked at the grub/hex-screw mechanisms. One hex-screw was loose, so I tightened it to hand tight and let the grub-screw off an eighth of a turn. I'll look again this evening.
I ran a three hour sequence of exposures on NGC6888 (with dither) and this is what I got on EVERY image. Amazingly, they stacked nicely.
So last night I ran without dither and it was mostly OK. What I want is full dither, but to do that I need to deal with the backlash.
Here's a photo of the motor and gears, most of the backlash seems to come from the top gear (ie the 12-tooth gear and its neighbour). I guess the rest comes from the worm-gear:
Does anyone have any suggestions? There doesn't seem to be a belt-mod for the EQ5 as far as I can see. Maybe there are better Dec backlash compensation settings I could use.
Hi, I recently made a video of how to mount a Sesto Senso focus motor to a Starlight feather touch focuser.
I have now also made a video of how to calibrate it and also how to measure the backlash of the rack and pinion gear of the focuser.
This method is not limited to a starlight feather touch focuser but could be performed on all kinds of focuser.
I hope this video makes it easier for anyone out there having problems with backlash.
You can also check out my other videos of the focuser / focus motor here: https://www.youtube.com/channel/UCm50WzpT1YKCwghW13b6k-g?view_as=subscriber
I've set my scope up on it's pier in my ROR observatory, done a few drift aligns and started to take some images.
I've noticed a 'quite' regular dip in my DEC line on several nights.
Would anyone be able to have a quick scan of my log and offer any insight?
Could it be backlash? Could it be something with each rotation of the gears? Faulty tooth?
It is quite regular, although not always, and always in the same direction.
It doesn't seem to be adversely affecting imaging yet, but I've not tried anything too taxing.