TheSkySearchers

Hello everybody,
I have a Celestron AVX mount, the last two time out I've had a problem. I power up, move to the index marks, yadda, yadda, yadda. Once I've done the final step ASPA I enter in my first target. It slews to the target so I go to PHD2 and set up there, pick a star and start guiding. Back to Sharpcap where I'm setting up the camera to begin setting up for exposure times. Looking at the sreen with 2 second exposure time the stars a drifting N to S. I look at PHD2 the RA line is taking a dive.......so I watch the stars there. Same thing they are drifting. I decided after awhile to just restart the mount and try again. Power up, yadda, yadda, selected previous alignment. Everything seemed to be settled down now and running smoothly. Tonight it was Deja Vu all over again except power off/back on didn't seem to help. Tonight turned out a bad night to be out anyway so I packed it up and came in.

Anybody had this problem before? What did you do to fix it?

Thanks,
Dano

P.S. I was running off of a freshly charged power pack.

Sounds like backlash to me.

Try to approach your imaging target (your final movements to center) using the up and right buttons on the hand controller. This way your RA and Dec gears stay loaded.

If you have to use your down and left arrow keys, you are taking the load off the gears so the mount will remain idle until the gears mesh again. This allows the field to drift for a few seconds.

Two things that might help with PHD2 is to: 1) redo your calibration and always remember to slew for a few seconds to the north (use the UP button on your HC) BEFORE you start the calibration. 2) Always run the Guiding Assistant (GA) AFTER the Cal plus start guiding before you run the GA, it will provide a ton of useful information, like how big your min move needs to be.

Hope this helps,
JT

Thanks, I always do the up/right to center a star and tried to re-do Calibration and GA. Like always it had the AVX DEC backlash. Neither helped. Last week it was running so smooth, PHD2 ran like silk but it is poop now.

Dano

Astroglide65 wrote: ↑Mon Dec 02, 2019 1:35 pm Thanks, I always do the up/right to center a star and tried to re-do Calibration and GA. Like always it had the AVX DEC backlash. Neither helped. Last week it was running so smooth, PHD2 ran like silk but it is poop now.

Dano

I had similar issues and found the RA clutch knob was hitting the plastic motor/gears cover when slewing to the NE.

You can hear the difference in the tracking motors when you do the up-right arrow combination ( maybe not outside ).

Last night I tried again got the same results. Did everything by the book even reset to factory settings. Slewed to the moon it seemed to be stable, slewed to Altair and after a few minutes it still drifted.

Astroglide65 wrote: ↑Tue Dec 03, 2019 2:00 pm Last night I tried again got the same results. Did everything by the book even reset to factory settings. Slewed to the moon it seemed to be stable, slewed to Altair and after a few minutes it still drifted.

So after a factory reset, the Moon remains in the FOV and no movement, yet Altair drifts? That sounds like the incorrect tracking speed, as if you are on lunar and not sidereal.

Do you have SharpCap configured to control the mount? If so, what tracking speed is SharpCap set at?

Just shooting spit balls here. This is very strange indeed.

Are you getting a rocking motion? Do a live view on the camera without auto guiding and and zoom in on a star. Sometimes having the wrong exposure length can give rocking from chasing the seeing, but usually only shown with short durations ie 1 sec and under.

I'll check the tracking speed tonight. No Sharpcap isn't controlling the mount but I may give CPWI control and see how that goes. I deleted the set up in PHD2 and put it back in and did the dark shots. Will see tonight. No it doesn't appear to be rocking, it slowly moves to the right on the screen. Could the HC be the problem? Is there an update on the firmware available?

I have little hair left........
Dano

Another tip from an AVX user... When balancing the RA, make it a tiny bit "East heavy'". That's an old indian trick to keep the gearing snugged up.

I would try setting your mount to the index marks by releasing each clutch before you power up the mount.

Are the gears too tight? Maybe the steppers experience too much friction. Mechanical things can happen sometimes and sometimes not. Open it up and check and loosen the worm gears if needed. Other than that, assuming you set DST and location correctly, I would double check the power, there are plenty of cheap jump starters that should work great. If you have the gears opened up that's also a good opportunity to set the backlash compensation, works like a charm. Don't give up, a mount is a straightforward piece of gear and the AVX is very good for the money.

East heavy....yup done that.
Index marks.....yup I center then up then power up and center them again each time.
Gears are fine, I just recently took out some slop but made sure I didn't go to far.
DST is turned off and after Factory Reset Time, Location etc. double checked.
Power doesn't seem to be the problem, fresh charged and had experienced slow loss of power from dying battery before. The sound of gears turning is same pitch and no sound of dragging. I did hear something I never heard before. I was calibrating PHD2 again and as it did the backlash ting I heard "click,click,click about 10 times sounding like it came from DEC.
Going camping tonight and tomorrow, we'll see how it goes.

Thanks everybody,
Dano

I've had this same issue to a certain degree with all my Celestron mounts... Very annoying.
One solution I've found that seems to just about always work... Using the hand controller, scroll to tracking. turn it off. Just for a few seconds. watch the screen while you do this and you can confirm the star movement picks up. then restart in North tracking, (or South depending on your hemisphere of choice). That usually fixes it. It's almost like the mount loses its mind for a second.
I agree it could be backlash, but the settings would have to be very high, (>40 or so) to cause that kind of continual movement, I would think.
Hope this helps!
Cheers

JimMinCT wrote: ↑Wed Dec 04, 2019 6:07 pm I've had this same issue to a certain degree with all my Celestron mounts... Very annoying.
One solution I've found that seems to just about always work... Using the hand controller, scroll to tracking. turn it off. Just for a few seconds. watch the screen while you do this and you can confirm the star movement picks up. then restart in North tracking, (or South depending on your hemisphere of choice). That usually fixes it. It's almost like the mount loses its mind for a second.
I agree it could be backlash, but the settings would have to be very high, (>40 or so) to cause that kind of continual movement, I would think.
Hope this helps!
Cheers

Thank you so much, can't wait till I have the problem again 'cause now I have a remedy!
Dano