EQ6 refurb tracking walking or zigzagging?

[Leeps]

Hi all, 

I am refurbishing an EQ6 mount, took it out last night for a first run. After setting up, the goto seems to work great, but when I got the DSLR set up, the tracking doesn't seem that great. I noticed trails on the first few exposures, so I undid the alignment and redid the polar align. Once I made sure that looked good (I think it may have moved, the alt bolts suck) I set back up and did a bunch of 2 min exposures. Some of them give larger trails than others, and it seems to be walking in 2 directions! Anyone have any idea? 

Here is a gif of me going through frames

The mount has had a new motor but on the dec axis, so I was thinking that wouldn't make too much issue with tracking...?

Any help would be fantastic, and any advice on if there's some calibration or motor setup features I need to do...?

[michael8554]

Two directions suggests Periodic Error on RA, and backlash on Dec.

You say the PA looked good ? The overall movement across the sky suggest it wasn't very good.

Michael

Edited May 2, 2020 by michael8554

[newbie alert]

Any play in the axis if you give then a good wiggle?

[knobby]

What did you do to the mount apart from replace the motor ?

Sounds like something is meshing too loose or to tight maybe.

[Leeps]

8 hours ago, knobby said:

What did you do to the mount apart from replace the motor ?

Sounds like something is meshing too loose or to tight maybe.

I only replaced the motor, and soldered up some connections. I was a little worried that it might have taken a knock in transit, the RA axis does wiggle a bit...

11 hours ago, newbie alert said:

Any play in the axis if you give then a good wiggle?

Yeah a bit. I managed to break my old mount by messing with backlash, so I was hoping to avoid it! Do you know a good guide to do it? I also thought it might not matter so much, as the RA axis is being driven, I didn't think it'd show up

21 hours ago, michael8554 said:

Two directions suggests Periodic Error on RA, and backlash on Dec.

You say the PA looked good ? The overall movement across the sky suggest it wasn't very good.

Michael

I think it was good, barring the alt bolts. It's a pain now because I have to wait for and waste another clear night figuring it out! 

[newbie alert]

11 hours ago, Leeps said:

23 hours ago, newbie alert said:

 

Yeah a bit. I managed to break my old mount by messing with backlash, so I was hoping to avoid it! Do you know a good guide to do it? I also thought it might not matter so much, as the RA axis is being driven, I didn't think it'd show up

How did you mess the old mount up trying to dialnout the backlash?

Astrobaby did a guide,  on a full strip down and relube, but it may just need the worm adjusting, simple to do but takes time to get it the best you can, compromise on tight enough so you haven't any play and too tight to avoid locking up

http://www.astro-baby.com/EQ6 rebuild guide/EQ6 Strip Down Home.htm

Edited May 4, 2020 by newbie alert
Added info

[newbie alert]

This one on worm adjustment

http://www.astro-baby.com/EQ6 rebuild guide/EQ6 worm alignment.htm

[Leeps]

Excellent, thanks. I guess that's step one! I'm a little paranoid that it got a little thrown about in transit, and I'm hoping there's not a bent worm, but I'll try to finesse it and report back. 

[Leeps]

Well, small update while we enjoy these cloudy skies 😞

 

I adjusted the RA as best I could, got rid of the play nicely. It turns full round with no real snags, so that's good. One weird question, should the RA axis turn both ways when turning at rate 1? I can't hear it turning in the left direction when I have it on rate 1, but all other directions I can hear the motor modulation - seems a bit strange. 

 

I'll get out and see how this aligns once we have the weather.

[michael8554]

I'm not familiar with your mount but I'd guess rate 1 is the same as Sidereal. 

So it slews west at +1, but just stops the drive to move east at -1.

MIchael

[Leeps]

Ah, that makes perfect sense. This place is great for learning