AM5 Simultaneous Guiding Spikes - Forums

My last two sessions with my (new to me…) AM5 haven't gone as I'd like. I mostly image with an NP101 and use a 120MM Mini hooked to a WO 32mm Uniguded (120mm FL).

I used to have the following defaults:

Guide rate = 0.5X
Guide exposure = 1 sec
Calibration step = 2500 ms
Max Dec = 2000 ms
Max RA = 2000 ms

I've always set up on a hard surface with this mount using the TC40 tripod. I used a 3D printed pier extension because, well, it's much cheaper than the ZWO version.

I would get these weird, random spikes simultaneously in RA and DEC. I can understand a spike in one direction but not in BOTH and of considerable magnitude (>4", lasting a few seconds). The guiding otherwise was ~0.5" and really good but that's enough to screw up subs.

Last run I dropped the calibration step to 1700 ms but still had the *&^%$#@ spikes, costing me ~10% toss rate on subs. I then adjusted the parameters to:

Guide rate = 0.5X
Guide exposure = 0.5 sec
Calibration step = 1700 ms
Max Dec = 400 ms
Max RA = 400 ms

I still get spikes, but they're more muted (typically <2") and resolve MUCH faster (<1 sec), apparently fast enough that I'm now getting nice, round stars. So that's good.

But what's up with spikes that are happening in both DEC and RA at the same time? Should I send my mount in for repair?

Clear Skies,
Phil

Can you post a PHD2 log?

I have an ASIAir and I'm not sure how to post a log of it. Can't even screenshot it with my phone since my phone runs the ASIAIR.

Clear Skies,
Phil

Phil Creed:
my phone runs the ASIAIR

Maybe send a screenshot of your phone?

What are your RA and DEC Aggr(essiveness) settings? Typically, the AM5 likes fast exposures (around 0.5 s, like you have) and low Aggr settings (around 25-30%). Just something I played with to improve my guiding. Not sure about your <quote> *&^%$#@ spikes <quote>.

I have the exact same issue.
Calibration step 1800
Max RA 250
Max Dec 250
Aggressiveness 35

Randon spikes of about 2" in both RA and Dec at the same time. Things recover pretty quickly but I can't figure out what's causing the spike.

Wanted to add that I have read some random comments about PA creep in Altitude with the AM5, I will try tightening things up really well tonight and see if it make a difference.

same for me on AM3. I think its got do do with the guide star illumination. I noticed if i get less than 200 on the guide star peak reading it can cause guiding loss for a nano second hence both ra and dec affected. I have a guide rate refresh at 0.5 sec. I then turn up gain and make the whole field brighter and it fixes the issue slightly. But I noticed that guide star peak can change throughout the night so i need to up the gain every now and then. Not sure its your problem, and Im not sure spikes are caused only by that issue but since moving to harmonic mount i have never had 100% spike free guiding. It doesnt affect my subs if the spikes are close to my pixel scale. I get less of this when using OAG

Phil Creed:
my phone runs the ASIAIR

Maybe send a screenshot of your phone?

What are your RA and DEC Aggr(essiveness) settings? Typically, the AM5 likes fast exposures (around 0.5 s, like you have) and low Aggr settings (around 25-30%). Just something I played with to improve my guiding. Not sure about your <quote> *&^%$#@ spikes <quote>.

That might be one of my issues. I think I was 50-60% aggression on both RA and DEC.

Clear Skies,
Phil

Phil Creed:
I have an ASIAir and I'm not sure how to post a log of it. Can't even screenshot it with my phone since my phone runs the ASIAIR.

Clear Skies,
Phil

Found out recently myself but phd2 logs get saved in the 'logs' folder either on the asiair itself or on whatever storage device you have attached to it.

I don't really understand what the logs will show that is helpful.

Solid 0.3-0.4 RMS with random spikes where Dec and RA spike at the exact same time. Seems to be guiding great and then something goes away…

The spikes are usually about the same size, spiking to around 0.7-0.8

The recovery of the spike seems quick, and both the RA and Dec are back to flat in short order.

However there doesn't seem to be a known cause of the spike. No logs will show why, it just shows that it occurred, exactly as I'm describing here

In my case I have ruled out
Seeing. ( This is just too short to be seeing)
Wind ( happens with no wind, and high wind shakes do not perform similarly on the same mount/settings)
Ground stability. ( Happens on solid cement)

There is also no pattern to how often. Sometimes it is less than 60 seconds, sometimes is greater that 3 minutes. Super random.

The quantity of the size of the spike seems to be constant. Meaning the spike size and recovery time for the spike doesn't seem to change. The only variable is how often it occurs.

I also just verified this occurs the same way with my asiair and with PC level guiding with php2

If there is some kind of PA slipping it could be an answer but beyond that, I'm concerned my mount is broken.

Well, let's see if we can find some commonalities here.

For those having the spikes, do you use a pier extension, either ZWO or other? The idea that PA might slip somehow is intriguing.

Ultimately what matters is how tight and round the stars are, so if it's just a case of adjusting settings to account for the mount's quirks it's not so bad. If it's a sign of worse thing to come, maybe a different story.

I can say this–I wasn't having issues until I used a 3D printed pier extension. But that could easily be a post hoc fallacy.

Clear Skies,
Phil

I had similar (4 arc-sec) random RA/DEC spikes not as a result of guiding impulses or periodic motion on my AM5 utilizing a 120mm guide scope and 220MM camera. I reached out to the PHD2 Google Group, and one of their developers immediately called out how my guide scope was mounted to my telescope, which was two set screws holding it within a shoe. To me it seemed sufficient with my short focal length (~400mm). However, with my guiding ratio, they equated a 4 arc-sec spike to 2.6 microns of movement of the guide scope relative to the main scope/mount, a human hair is 50 micron.

With that said, I switched to an OAG, and the spikes went away. I could have also looked to more firmly mount my guide scope to my scope.

Just a suggestion, good luck troubleshooting.

-Chris

I had similar (4 arc-sec) random RA/DEC spikes not as a result of guiding impulses or periodic motion on my AM5 utilizing a 120mm guide scope and 220MM camera. I reached out to the PHD2 Google Group, and one of their developers immediately called out how my guide scope was mounted to my telescope, which was two set screws holding it within a shoe. To me it seemed sufficient with my short focal length (~400mm). However, with my guiding ratio, they equated a 4 arc-sec spike to 2.6 microns of movement of the guide scope relative to the main scope/mount, a human hair is 50 micron.

With that said, I switched to an OAG, and the spikes went away. I could have also looked to more firmly mount my guide scope to my scope.

Just a suggestion, good luck troubleshooting.

-Chris

Thanks Chris
Thoughtful advice. Ill take a look at my setup. I'm using the asi2600 mc duo. So no real guidescope. But... I can see ways the whole setup could be mounted more firmly. Maybe the whole scope is slipping around.

Phil Creed:
I have an ASIAir and I'm not sure how to post a log of it. Can't even screenshot it with my phone since my phone runs the ASIAIR.

Clear Skies,
Phil

btw, asiair also saves guide logs, just look in those folders (where your subs are), there should be one named logs and everything is in there

Phil Creed:
Well, let's see if we can find some commonalities here.

For those having the spikes, do you use a pier extension, either ZWO or other? The idea that PA might slip somehow is intriguing.

Ultimately what matters is how tight and round the stars are, so if it's just a case of adjusting settings to account for the mount's quirks it's not so bad. If it's a sign of worse thing to come, maybe a different story.

I can say this--I wasn't having issues until I used a 3D printed pier extension. But that could easily be a post hoc fallacy.

Clear Skies,
Phil

I do have the ZWO pier extension on the tc40 tripod, and trying it without the extension is an easy enough task.

Round stars? Yes until I exceed 180 second subs, but keep in mind this setup is only 300mm, so when I start using a larger scope ie 800mm this will be a much bigger concern.

As of now I have the following things to try.

Check the PA knobs to ensure it is tight and no slippage
Try to make my last Altitude adjustment (UP) to make the screw is under tension
Try ditching the Pier Adapter
Double check my scope/camera are not slipping or moving around

I also found some math that suggests I should be using max calibration size of 733 due to my pixel scale and the guide scope being 300mm with the dual (will try that too)

If I am honest none of these seem like a silver bullet, but at least it gives me something to try.

Thanks for the suggestions.

I had similar (4 arc-sec) random RA/DEC spikes not as a result of guiding impulses or periodic motion on my AM5 utilizing a 120mm guide scope and 220MM camera. I reached out to the PHD2 Google Group, and one of their developers immediately called out how my guide scope was mounted to my telescope, which was two set screws holding it within a shoe. To me it seemed sufficient with my short focal length (~400mm). However, with my guiding ratio, they equated a 4 arc-sec spike to 2.6 microns of movement of the guide scope relative to the main scope/mount, a human hair is 50 micron.

With that said, I switched to an OAG, and the spikes went away. I could have also looked to more firmly mount my guide scope to my scope.

Just a suggestion, good luck troubleshooting.

-Chris

Maybe I do need an OAG. Or a Duo/Air version of the 533. Very frustrating as a DSO imager to see a 585 Air but no 533 Air/Duo.

I currently mount the guide scope onto the Vixen slot included in the William Optics saddle handle bar. At least I thought it was tight but if this is the cause, maybe not tight enough.

Clear Skies,
Phil

Phil Creed:
I have an ASIAir and I'm not sure how to post a log of it. Can't even screenshot it with my phone since my phone runs the ASIAIR.

Clear Skies,
Phil

Asiair save phd2 log in a folder.

Honestly I'm struggling with some kind of spikes since I purchased the AM5. I even returned one, since I was unable to get below 1.3" total RMS. The new one is better so I still have it (about two years), but far from those steady lines posted by other people. In average it guides around 0.7". There are some nice periods for maybe a minute of 0.3" and suddenly there is a spike/shake. Sometimes DEC and RA are in sync, sometimes not. It is typically reversed very fast, but then it must go other direction again. Aggression has no effect on that nor any other settings. I have no idea if this is seeing, the mount, tripod or maybe a mole under our garden. I tried different tripod, pier extension, better guiding camera and better guide scope. Those regions in-between seemed to be improved by those changes, but not the spikes.

Most importantly, the stars are still round and mostly I don't need to reject frames because of bad star shape. Even with 300s on Askar500 with 533MC PRO. So I gave up and I'm slowly learning to live with that :-)

ummm.. Ok.. so the graph literally tells you what the 'problem' is… Between every exposure, your system is dithering. This is where it moves the guide star a sufficient amout so as to make each sub exposure ever so slightly misaligned. this results in better colour correction for one shot colour cameras, and results in reduced fixed pattern and walking noise in the final stacked image (for mono or osc)

These are intentional, and configured by you.

The reason you're not seeing elongated stars is because this happens at the end of each sub exposure, and the guiding system waits until it is sufficiently settled before telling your imaging software that it is time to commence the next sub exposure.

This is PERFECTLY normal - and there is absolutely no reason to return your mount or be concerned at all..

Alex Nicholas:
ummm.. Ok.. so the graph literally tells you what the 'problem' is... Between every exposure, your system is dithering. This is where it moves the guide star a sufficient amout so as to make each sub exposure ever so slightly misaligned. this results in better colour correction for one shot colour cameras, and results in reduced fixed pattern and walking noise in the final stacked image (for mono or osc)

These are intentional, and configured by you.

The reason you're not seeing elongated stars is because this happens at the end of each sub exposure, and the guiding system waits until it is sufficiently settled before telling your imaging software that it is time to commence the next sub exposure.

This is PERFECTLY normal - and there is absolutely no reason to return your mount or be concerned at all..

I'm aware of dithering, however it's disabled for this troubleshooting.

The graph shows random spikes without dithering enabled and in the middle of taking subs

I just came in from trying some new things and have pretty good results.

Previous RMS was 0.9 with the random spikes going up to 3.0 or 4.0

Current RMS O.41. Still have the random spikes but they are generally under 2.0

I'm pretty happy with 0.41 as an average.

Ultimately what fixed this is a combination

1. I removed the PE160 pier from my tripod and replaced it the PE200

2. I firmly tightened all knobs after my PA

3. I added 20 lbs to my tripod basket

4. I powered my mount directly instead of via my asiair

I'm not saying this is perfect but these numbers are very usable and I took a few 300 second subs for testing and I get round and beautiful stars.

Id be willing to bet that adding a counterweight would help too but I haven't tried that yet. (Might try that another night)

I think..... Based on testing and my gut...

The tc40 tripod is sturdy but needs weight on it to avoid micro movements.

The AM5 mount slips in its alt az while guiding or slewing, unless you tighten all the knobs after the polar alignment

The asiair doesnt always do well powering larger things like a mount or power consuming cooled camera

The pe160 pier extension is cute, but semi flimsy. The PE200 is much better.

Just my results.

Some of what I’m seeing is consistent with wind spikes. Mid-priced mounts are more susceptible to this, but otherwise, properly adjusted, can rival premium mount performance.

Harmonic drives benefit from a different approach to guiding. Some responses above allude to it but their suggestions need to be modified further. For some reason, the industry does not mention this often, and I don’t know why.

I have an old AM5 at Starfront, in Texas, and regularly get 0.3 to 0.6 guiding all night long with the following numbers:
Max RA/DEC: 140ms/140ms
Guide speed: x0.75
exposure: 0.5sec
Aggression: 25% (30% in more turbulent skies. As always, adjust to taste as conditions require)

These settings prevent the guide adjustments from riding on top of the periodic error, reducing guiding errors significantly. It’s visible in the graph, with the fluctuating corrections moving together in a straight line, the PE sine wave almost completely subtracted. Stars are smaller and perfectly round.

The dithering spikes will continue and contribute to lower noise in the final stack. It’s just a slight repositioning of the image and completely normal. But some of the aberrations you have been getting should be greatly reduced.

Secret tweak: RA guide results are usually higher than DEC. Try shortening the RA Max to 135 or even 130. Leave DEC at 140. You’ll see the RA guide number drop immediately…equaling DEC much of the time.

With these applied to my AM5, the guiding is equal to my home traveler ioptron harmonic…and it has encoders!

Just to be clear, I am aware of what dithering is and I do it intentionally. My problem clearly is the crazyness between. The zoomed peak is not dithering but a random spike during exposure. I gues I will try adding some weight.

New information to share

After a little t of trouble shooting I improved a lot but still have small random spikes in guiding

After reading a reddit post I was pointed towards voltage

For kicks
I put the AM5 on its own power supply and did not use the AM5 passthrough to power anything else.

And…

Well I can't say for sure but in over 1 hours of testing last night. There were zero spikes. I had 0.23 guiding.

Now there's more testing to do but I'm excited

Dave Rust:
Some of what I’m seeing is consistent with wind spikes. Mid-priced mounts are more susceptible to this, but otherwise, properly adjusted, can rival premium mount performance.

Harmonic drives benefit from a different approach to guiding. Some responses above allude to it but their suggestions need to be modified further. For some reason, the industry does not mention this often, and I don’t know why.

I have an old AM5 at Starfront, in Texas, and regularly get 0.3 to 0.6 guiding all night long with the following numbers:
Max RA/DEC: 140ms/140ms
Guide speed: x0.75
exposure: 0.5sec
Aggression: 25% (30% in more turbulent skies. As always, adjust to taste as conditions require)

These settings prevent the guide adjustments from riding on top of the periodic error, reducing guiding errors significantly. It’s visible in the graph, with the fluctuating corrections moving together in a straight line, the PE sine wave almost completely subtracted. Stars are smaller and perfectly round.

The dithering spikes will continue and contribute to lower noise in the final stack. It’s just a slight repositioning of the image and completely normal. But some of the aberrations you have been getting should be greatly reduced.

Secret tweak: RA guide results are usually higher than DEC. Try shortening the RA Max to 135 or even 130. Leave DEC at 140. You’ll see the RA guide number drop immediately…equaling DEC much of the time.

With these applied to my AM5, the guiding is equal to my home traveler ioptron harmonic…and it has encoders!

Dave,

Hope you don't mind me asking...

Question 1 -- what benefit does setting the guide speed to 0.75X reap vs. 0.50X?

Question 2 -- what would likely result if I used all the above settings, but maintained a 1.0-sec guide exposure? I'm pondering a Duo / Air and I'm worried about short guide exposures when using dualband filters.

To all -- thanks for the feedback. There's a lot more variables than I thought to optimizing guiding performance and I really appreciate it. Just another why I feel there's no hobby on earth better than amateur astronomy (...but I might be sliiiiightly biased!)

Clear Skies,
Phil

I just want to toss in here my 2 cents.

When you see spikes in BOTH axes at the same time, these are indicative of external forces acting on the mount, such as wind or something bumping it. In most cases I would completely ignore those spikes. Also, guiding is only as good as your seeing conditions. Some folks don't ever see good guiding, particularly those in turbulent mountainous areas.

In Martin's screenshot above I do see one glaring issue however. His MnMo for his dec is set too low, causing oscillation in the dec axis. Relaxing this setting will iron most of that error out.

Hey, Phil!

the x.75 just makes it easier for the mount to accomplish the intended correction on such a short time.

you can change any of the values as you wish. The approach is designed to avoid creating oval stars that are generated by longer correction times and harmonics’ larger PA curves. If you try 1sec and like the results, fantastic! On my gear the total guiding number dropped noticeably with 0.5sec, but I bet either time would lead to usable results.