PHD2 Guiding Help Required

[A320Flyer]

Hi,

I have a new EQ6R-Pro mount and recently moved over to NINA for imaging, which entails using PHD2 for guiding.

I have calibrated succesfully, run the Guiding Assistant, applied the recommendations, run the PPEC Training in GS Server and enabled the PPEC.

After adjusting the guiding agressiveness for RA and Dec, I can achieve a Total RMS Error of around  0.7-1.0 on a typical night. 

My issue is that RA rms is always worse than Dec rms (usually by a factor of around 3). No matter what adjustment I make , I cant seem to improve this.

Is this typical? Should the rms errors not be very roughly similar on each axis? My stars are usually quite round, although I suspect they could be a little tighter.

I have attached last night's guide log. The two longer periods of guiding are those at either side of the meridian flip.

Can anyone offer any explanation or advice?

Many thanks

Bill

 

PHD2_GuideLog_2022-02-27_190003.txt

 

Edited February 28, 2022 by A320Flyer

[michael8554]

Hi Bill

There isn't a Calibration or Guide Assistant run in your Log, but Calibration and PA seem to be good.

Dec guiding is good, Dec = 0.32arcsecs

RA is twice that, RA = 0.66arcsecs.

Your RA tracking has a significant 10 second period spike that is often seen in belt-drive mounts:

 

PHD2 will find it very hard to guide out such a fast transient.

Not a EQ6R-Pro user, but from what I've read it may be a matter of belt tension adjustment, and/or moving the belt a few teeth on the cogs.

And PHD2 Predictive Periodic Error Correction (PPEC) for the RA Guide Algorithm, at a fixed setting of 10 secs.

Hopefully EQ6R-Pro users can provide clarification.

Michael

 

[A320Flyer]

Thanks for that, Michael. As you suggest, I’ll wait to see if any eq6r-pro experts chip in. 
Bill

[wimvb]

The 10 s period is caused by a belt that is too loose. You just need to remove the RA belt cover and tighten the belt a little. I had the same with my AZ-EQ6 and this fixed it.

Btw, have you tried guiding without PPEC (does the EQ6-R have mount stored PPEC?). The Predictive PEC guiding algorithm in PHD, together with multi-star guiding usually gives good results.

Edited March 1, 2022 by wimvb

[A320Flyer]

1 hour ago, wimvb said:

The 10 s period is caused by a belt that is too loose. You just need to remove the RA belt cover and tighten the belt a little. I had the same with my AZ-EQ6 and this fixed it.

Btw, have you tried guiding without PPEC (does the EQ6-R have mount stored PPEC?). The Predictive PEC guiding algorithm in PHD, together with multi-star guiding usually gives good results.

I’ll give the belt a little tighten tomorrow 👍

I understand from the developer of GS server that it writes the ppec to the mount. Guiding is a little better with ppec enabled than without. 

Thanks. 

[A320Flyer]

Just an update:

I managed to get the roof open this morning and have a look at adjusting belt tension. On removing the two small access panels for the RA and Dec, a fair amount of rubber swarf was evident. Using a soft brush and a substantial amount of lung power, I cleaned in and amongst the gears and belt teeth. The belts themselves seemed to be adequately tensioned but the adjusting grub screw on the RA axis was quite loose. I nipped this up to finger tight and closed up the access panels. 
Now, it’s forecast to be 100% cloud cover here for the next four days but I will test my guiding at the first available opportunity and report back. 

Bill

[Skipper Billy]

5 hours ago, A320Flyer said:

On removing the two small access panels for the RA and Dec, a fair amount of rubber swarf was evident.

If there is a lot of rubber swarf it might be prudent to fit new belts - they are very cheap.

[wimvb]

5 minutes ago, Skipper Billy said:

If there is a lot of rubber swarf it might be prudent to fit new belts - they are very cheap.

 

5 hours ago, A320Flyer said:

Just an update:

I managed to get the roof open this morning and have a look at adjusting belt tension. On removing the two small access panels for the RA and Dec, a fair amount of rubber swarf was evident. Using a soft brush and a substantial amount of lung power, I cleaned in and amongst the gears and belt teeth. The belts themselves seemed to be adequately tensioned but the adjusting grub screw on the RA axis was quite loose. I nipped this up to finger tight and closed up the access panels. 
Now, it’s forecast to be 100% cloud cover here for the next four days but I will test my guiding at the first available opportunity and report back. 

Bill

Beltingonline.com is your best friend for these matters. The belts are T2.5 if I recall correctly. It's good to have a spare belt or two, just in case. You might also want to check why there was a lot of swarf.

[A320Flyer]

Thanks guys. I’ll look into that 👍

[michael8554]

Edge damage to the belt might indicate the cogs are offset.

Michael

[A320Flyer]

20 hours ago, michael8554 said:

Edge damage to the belt might indicate the cogs are offset.

Michael

Something else to look at. Thanks. 

Edited March 5, 2022 by A320Flyer

[juno16]

On 01/03/2022 at 14:52, wimvb said:

The 10 s period is caused by a belt that is too loose. You just need to remove the RA belt cover and tighten the belt a little. I had the same with my AZ-EQ6 and this fixed it.

Btw, have you tried guiding without PPEC (does the EQ6-R have mount stored PPEC?). The Predictive PEC guiding algorithm in PHD, together with multi-star guiding usually gives good results.

Very good to know as I will upgrade my HEQ5Pro mount very soon with the Rowan kit. I assume that a loose belt on the HEQ5 would also induce a similar period in RA. Thanks.

 

Jim

[wimvb]

1 hour ago, juno16 said:

I assume that a loose belt on the HEQ5 would also induce a similar period in RA.

Most likely, but probably not at exactly 10 s. Just guide for a reasonably long time (half an hour at least, an hour preferrably) with 1 s guide exposures. Then load the guidelog into PHD Log Viewer and do a frequency analysis. This should show the most important peaks. The worm period will probably not be that well resolved, but it's the least interesting, because it will be guided out.