Is this guiding OK after belt mod

[geoflewis]

1 minute ago, blinky said:

Hi,

Thanks for taking the time to look and comment - The swap to the 2nd scope is just that, comeplete removal of Newt and stick on Frac - as you say I never did another GA as I forgot.  I think I also disabled the PEC in EQMod and redid it, so it would have kicked in at somepoint in the run.  Today I removed a little more backlasg from RA and tightened the worm end ring a little more then made sure it was not binding.  Its also currently sitting tracking in RA so I can 'run in' the bearings and spread the grease about a little more...... Tonight looks good for another run!

Backlash in RA has no impact on guiding, as the gear drive is always moving in the same direction - for RA the guide pulses just change the rate of movement, i.e. speed up or slow down the gear. Backlash in Dec is the problem as when a change in direction from north to south is required then the guide pulses have to take up the backlash before the mount actually changes direction, hence there is a delay, quite often followed by an overshoot and then a reverse correction leading to guiding oscillations.

Good luck tonight.

[blinky]

So what affects guiding in RA if backlash has nothing to do with it? - Im not disputing this BTW, just asking...

[geoflewis]

43 minutes ago, blinky said:

So what affects guiding in RA if backlash has nothing to do with it? - Im not disputing this BTW, just asking...

Sorry, just been out for a 4 mile walk with my wife and very pleasant it was too despite the fairly strong chill east wind - I hope that drops by this evening BTW.

OK so the primary issue seen with RA is periodic error (PE), which arises from errors in the gear train, e.g worn, or poorly manufactured gears normal for other than very high end mounts and hence the use of PEC (periodic error correction) models. The worm gear is constantly turning and any errors in that will show up when that part of the worm engages the gear. Similarly errors in the individual gears will also show periodically and a pattern of errors will show repeating every complete worm cycle with the main frequency spike usually being the period of the worm itself completing a full rotation. PHD2 log viewer allows you to perform frequency analysis on sections of your guide log, but I'm not experienced in interpreting these, so again I would point you to the PHD Google Group for assistance, unless someone else on here can assist better than me. The other thing to be wary off with both RA and Dec is overtightening of the gear train as that may lead to stiction, (static friction) where the gears stick until sufficient force is applied to move them, this is seen by a build of in guide pulses that have no effect, then sudden large moves as the stiction is eventually overcome and the gears leap forward.