Hello,
I have an HEQ5 permanently installed on my garage roof. Bortle 8.
The mount is not modified and quite old (bought it used).
Polar alignment is good.
Guiding is OK but not great.
DEC guiding is quite good.
But I have annoying RA oscillations between 0.7 and 1.2" with 6-7 sec period.
I tried to adjust the guiding parameters many times but couldn't get rid of these oscillations.
The rig is reasonably balanced.
Tried with GPG on and off - same result.
Best guiding seems to be at 1.5 sec exposure.

Any suggestions on how to improve?
Thanks!
Below is the best I can do:
 
 

Hi Max,

I have a similar set up and always use GPG on. Try setting the worm period to 638.
I also usually bin my ASI120 at 2x2 and exposure from 1.5 - 2 sec depending on seeing
conditions. I never see long extended periods with oscillations because I dither every frame.

- Dean

Hi Dean,
How good is your guiding?
I also use GPG with 638 period.
Dither every 240-360 sec.
My oscillations are short - 6-7 sec.
Guiding with 1x1 bin. I did try 2x2 but long time ago. Will try tomorrow again.

I am planning to disassemble the mount and grease/tighten everything and see if it helps.
Tried this before but didn't have some special tools to unscrew everything. Now I have them.
Thanks!

Hi Max

I do not see any pulses in the drift graphics!? How is this possible (ST4?) ?

What are the effects of adjusting proportional gain ("aggressiveness")?

Could it be some overshooting by the guider algorithm?

BTW: I'm trying to implement a sort of "damping" by a derivative gain (classic PID). Until now there is a certain effect, but I don't know yet how far this will go.

Try 3 to 6 second exposures instead of the short 1.5.

I set my abort if guiding deviation > 1" ... most of the time I can get away with 30s exposures
with dithering every frame. Ill have to capture a log of my guiding to review the RA and DEC
RMS values to report further.

Thank you people!
Like I said, I tried pretty much everything, except maybe guiding exposure longer than 2 sec.
Will keep trying.

My total RMS is just above 1" with RA oscillations and occasional DEC excursions.
It's more than adequate for my FRA400 but not that good for RC6 at 1380 mm (which is the main scope for this mount).
Thanks!

Hi Max

It's me again. I  wasn't aware of the possibility to switch off the correction pulses: It's below the drift graphics window on the left to the "trace" bar. Your screen shot shows, that they are turned off.
So it would be very interesting to switch these on and to see how the mount is reacting!

No ST4. I just disabled corrections in the graph.
I tried all kinds of proportional gain.
The best combination for me is:
0.45   0.85
0        0
0.2     0.2
50      140
with GPG enabled and 1.5s guiding exposure.
_______________
I do not see any pulses in the drift graphics!? How is this possible (ST4?) ?
What are the effects of adjusting proportional gain ("aggressiveness")?
Could it be some overshooting by the guider algorithm?

I disassembled DEC and RA axes, regreased and adjusted mesh for gears/worm.
After that the behavior is about the same.
DEC is pretty good staying below 0.5" but sometimes going up to 0.8-0.9".
RA shows the sawtooth pattern, usually just above 1". Sometimes it goes lower but often runs away briefly.
Guiding improves as it gets darker. Usually close to Midnight.
I guess seeing / light pollution plays a role here.

The mount is old. I am at least the 3rd owner.
Probably that's the best it can do.
Time to upgrade.
I am thinking about GEM45. I wish they sell them without useless for me iPolar...

"6-7 sec period"
Hi
Move the driven gear on the motor a tooth at a time relative to the idler gear until the period lengthens. I got an old eq6 up to about 120s. Set the GPG period to that value.
Cheers and HTH

Alacant,
I am not sure I understand...
"Move the driven gear on the motor a tooth at a time" - what does this mean?
Right now all gears meshed together pretty tightly with almost no play.
Thanks!