Jump to content

stargazine_ep43_banner.thumb.jpg.ea2a27954a074b4478d83359648ce4e2.jpg

Guiding issues (EQ3 Pro mount): a detailed cry for help


Recommended Posts

Ok, please bear with me as this is may be a bit long and highly illustrated. I've tried to record my struggles as detailed as I could in the hopes of getting some help from you guys, so I beg you to read this carefully if you have experience with guiding issues and/or with the EQ3 Pro (SynScan) mount - I only got this mount about a week ago and I'm still wondering whether these issues is something that can be solved or to be expected, or whether I'm dealing with damaged goods.

So here we go. Bottom line, what is your judgement: is this correctable, is there something very wrong with the mount, or is this to be expected of this specific mount? I have until Friday to return this (14 day return policy), and if this is a lost cause, I'd like to know about it.

 

Two days ago I initially tried out this mount quickly, I managed to set it up and align it as a practise and fired up KStars/Ekos and PHD2 to see how this baby worked. Weather happened and I didn't quite get to the bottom of it - I did image for a few frames and quickly noticed that while initial calibration went ok, guiding was all over the place. Stars were very oblong on a 3 minute exposure. This didn't worry me much since the sky was getting cloudy and I therefore was a bit bad for testing, but I wanted to get a quick taste of it anyway.

 

Fast forward to yesterday. Skies were clear, and it was time for more testing. First of all I wanted to see how the EQMod driver worked (instead of using the SynScan driver), i.e. turning on the Direct PC Mode from the controller and going all computerized. No big issues there, except for the horizon limits which suddenly stopped tracking several times. Once I figured this out and disabled the limiting, no issues (except KStars/Ekos did not seem to save this setting). In any case, fast forward to guiding: again the PHD2 graphs were all over the place. A six hour of battle of calibrations/alignments/mount balancing ensued. It was not a pretty sight... in the end I decided to surrender to fight another day and swore that this time I'd properly document these issues. And that's where we are now.

 

So tonight I tried again. Let's start.

 

The mount was aligned quite closely to celestial pole from previous sessions. I re-balanced the mount, RA first, then DEC. I powered on the mount, set up date/time/location and engaged Direct PC Mode and fired up KStars/Ekos.

My balcony has no direct sight of Polaris, so I had to veer a bit off to the East to perform polar alignment with the Ekos. I ran the alignment procedure twice, and got pretty close. Finished the alignment using PHD2 Polar drift alignment tool, with PA Err 3 min after letting it stabilize for 3 minutes. Spent a good hour on the entire polar alignment procedure to make sure that a poor polar alignment wasn't going to be an issue.

 

At this point I was happy so I decided to navigate to a few stars and ran Ekos alignment.

After slewing to a target the captured camera alignment image looked like this:

 

7nyhwGZ.png

 

I have a settle time of 15 seconds on my alignment/solver - even then that's how it looks. The drift after running GOTO appears to be quite a lot. The backlash must be huge or something.

 

Alright, trying PHD2 guiding then:
Using ST4 guiding, since the mount supports it.
Calibration done pointing East. East-West movement looks good. 21 steps of clearing backlash. I make a note that the mount makes a click sound when moving north on every step.

Another note with South steps: virtually no movement whatsoever. Dist stays at ~29.

Result: Calibration completed but RA and Dec rates vary by an unexpected amount (often caused by large Dec backlash)
Calibration results as below.

 

5nQgkif.png

 

Guiding starts. The graph makes me want to cry. Dec is somewhat workable I think, but RA is bouncing all over the place.

 

HT9rM6Q.png

 

Running the Guiding Assistant next to get some insight.
Oh boy, no amount of polar alignment is going to fix this:

 

CLI8eab.png

 

Guiding assistant results below:

 

5F0oV4C.png5OjgNAh.png

 

Ok, so something's majorly screwed up here. I'm really hoping someone with knowledge can pitch in!

 

So let's try a star-cross test then. Might as well do everything while we're at it. In fact, let's do it a second time, and a third time in another part of the sky.

 

R7ca6tJ.png

 

Again, noticing from viewing live picture from PHD2 that the drift after slew is very noticeable and long.

 

Now again, for science, let's ditch ST4 guiding and go with mount only. After all there are probably differences!

Calibration East-West: the West direction appears to be flipped. West steps with ST4 went to the other direction! This just got interesting.
North-South direction is identical to ST4 however. Little south movement again.

 

K2RzEwn.png

RA is still flipping all over the place.

 

gANUGYY.png

 

Of course what really matters in the end is how the images look like. Obsessing over numbers is one thing and looking at actual images is another. So, let's take a look at a 180sec guided frame. The stars looks like this:

 

NIkSOZR.png

 

Not great, not terrible. But oblong and gets worse the longer the exposure gets.

I think I could work with the Dec, especially with all the settings to adjust it and the backlash, but the RA is just wreaking havoc.

This probably enough for now. On the previous night I literally tried balancing everything multiple times, even off-balance to both directions to see what the effect might be and yet this seemed to have no visible effect on the guiding graphs, everything jumped as wildly as in perfect balance. So that has been tried and tested. Also during that night the calibration without ST4 created absolutely wild results, with a huge overshoot East-West. Like this:

hNsYSN4.png

I really have no idea what was happening there.

In any case, it looks like the RM Error in Dec can be held within ~1", but RA easily goes over 2.5". And this is a real issue.

 

Bottom line, what is your judgement: is this correctable, is there something very wrong with the mount, or is this to be expected of this specific mount? I have until Friday to return this (14 day return policy), and if this is a lost cause, I'd like to know about it.

Thank you for reading! I'm gonna go sleep now and hopefully my subconscious can make something out of this.

  • Sad 1
Link to post
Share on other sites
21 minutes ago, jusasi said:

Oh boy, no amount of polar alignment is going to fix this:

Your PA looks fine, the Guide Assistant run reported 1.4arcmins, anything less than 5 is guideable.

The GA run shows the mount has Periodic Error, that's why RA is heading south off scale, but 15arcsecs isn't bad actually.

So RA could be tamed with Guide Rates upped to 0.8x and fettling of PHD2 settings, maybe try the PPEC Guide Algorithm?

You have huge out of spec Dec backlash, over 58.072 seconds, I'd return the mount with a print of that reading.

Michael

  • Like 2
Link to post
Share on other sites

Hi, at first glance i see similar things i've encountered with my EQM35-pro.

I have this mount since January and tried to use 3 times now, i had invested is a pocked powerbox, a USB hub and a small laptop to make this my second lightweight imaging rig, boy was that disappointing.

The aim was to use EQMOD without the HC directly trough a eqdir cable.

Calibration wouldn't finish, or return a prompt of "unexpected value's" or "star didn't move enough" etc.

Tried to guide with the HC and with ST4 cable, so no eqmod involved, no luck.

Basically, a gave up, i don't need this with a new mount, now its sitting there gathering dust, conclusion for me is don't buy anything less than a heq5.

Someone way smarter than me would probably adjust the eqmod settings, but i wouldn't know where to start.

I should have just returned it to FLO, or at least contacted them, but with all that bad weather we had in january, february and first half of march i'just didn't find the courage to keep on testing/trying

 

I hope you get this sorted, i will follow along, maybe there's a solution here

Link to post
Share on other sites
7 hours ago, michael8554 said:

Your PA looks fine, the Guide Assistant run reported 1.4arcmins, anything less than 5 is guideable.

The GA run shows the mount has Periodic Error, that's why RA is heading south off scale, but 15arcsecs isn't bad actually.

So RA could be tamed with Guide Rates upped to 0.8x and fettling of PHD2 settings, maybe try the PPEC Guide Algorithm?

You have huge out of spec Dec backlash, over 58.072 seconds, I'd return the mount with a print of that reading.

Michael

Thanks for the analysis!

Yeah, the Dec backlash seems bad - I might just go ahead and return it on that basis alone. If the skies stay clear enough I'll definitely try your tips.

Also I didn't mention my gear, I totally forgot:

 

- The scope is a 70mm refractor with 420mm focal length, reduced to 336mm with a reducer.

- The guide scope is a 50mm / 162mm focal length basic scope.

- The main camera is ASI1600MM, guide camera is ASI224MC.

- ASI filter wheel.

- Total weight of that setup is 3.8kg.

 

I bought the mount intending to use it as a travel mount, and figured from the specs that it would do fine for this load. It felt sturdy enough but looks like the machinery is a bit lacking. Also if it's finicky to get it to guide just right, it probably isn't exactly a the kind of mount I'd use for travel - I do not want to spend all night troubleshooting on-site after all.

 

1 hour ago, Miguel1983 said:

Hi, at first glance i see similar things i've encountered with my EQM35-pro.

I have this mount since January and tried to use 3 times now, i had invested is a pocked powerbox, a USB hub and a small laptop to make this my second lightweight imaging rig, boy was that disappointing.

The aim was to use EQMOD without the HC directly trough a eqdir cable.

Calibration wouldn't finish, or return a prompt of "unexpected value's" or "star didn't move enough" etc.

Tried to guide with the HC and with ST4 cable, so no eqmod involved, no luck.

Basically, a gave up, i don't need this with a new mount, now its sitting there gathering dust, conclusion for me is don't buy anything less than a heq5.

Someone way smarter than me would probably adjust the eqmod settings, but i wouldn't know where to start.

I should have just returned it to FLO, or at least contacted them, but with all that bad weather we had in january, february and first half of march i'just didn't find the courage to keep on testing/trying

 

I hope you get this sorted, i will follow along, maybe there's a solution here

So we're pretty much on the same boat here. Had that "star didn't move enough" once or twice on my first try as well.

I've now spent 3 days looking at this thing and wondering how to tame it, and had to come cry for help. Definitely not a mount for the inexperienced.

Link to post
Share on other sites

there is a topic here on SGL where you can see how you have to adept your values of phd-steps and such on. i encountered the problem 4.5 years back and it wasnt the mount or EQmod but PHD who needed some tweaking if i find the topic back, ill post the link

 

Link to post
Share on other sites

can't find the topic immediatly. and mine PHD2 is reseted due update 😪 ( last time i used it wa 4.5 years ago). 

but for as far i can remember :

 

open PHD

click on the brains

on the tab 'guiding there is a value for 'calibration steps' bump the 700 up to 1700 if i was correct ( if you have a short FL the 700ms doesnt suffice for your guide cam to deteect a movement)

and if i am correct , you can also go in the tab 'algorithms' you can bump up or down as well the max duration RA & dec.

 

if this doesn't help, i cant help you and only give the tip, check youtube, google or phd page.

 

 

Link to post
Share on other sites

Very long post which deserves a very long reply... Well, let's start from the gear: you're using an entry level mount to drive an APO with a high level CCD. Maybe you chose to save on the wrong end, but this being said, let's look at the graph and settings. 

You have serious obershooting in RA, due to an estremely high aggressiveness. Try lowering RA aggressiveness to 40-50 until corrections end up close to zero, slight undercorrections should be preferred. I don't see this to be the mount's fault

Now to dec: 58" backlash is enormous. It can usually be adjusted out easily (at least on non goto mounts), but I understand that it shouldn't happen on a new mount. You'll never get zero dec backlash but 58" (if the GA is right) is unmanageable. Try moving it North and South with the controller at a low speed: does it really take souch time before moving in the opposite direction? Did you select 0,5x or 1x as guiding speed? 

Two points here: Synscan has a settings to correct backlash, it could be used for smaller amounts. And, actually when guiding dec backlash can be ignored, you just need to do the following:

BEFORE calibration, move the mount North with the controller until all backlash is absorbed. 

Then perform calibration as usual. Ignore any complaint about insufficient South movement. 

Now leave PHD on its own for about one minute and assess direction of dec drift, and force dec corrections only in that direction. 

If drift is southward, move manually with controller until drift is absorbed again. From now on it should just be fine. 

I am a bit surprised that you tested the mount with guiding on your first outing, this makes hard to separate mount connected issues from those coming from the guiding. 

I'd make a Periodic Error measurement, because you could send back a perfectly working mount which just needs a bit of fine tuning. 

You could contact your dealer, but the question is: if you return it, is it worth to replace it with another EQ 3, or rather upgrade at least to an EQ5? 

I agree with previous comment: an HEQ5 is the solution I'd suggest (if your budget can stretch to that point) 

Good luck, 

Fabio 

Link to post
Share on other sites

hi Fabio,

 

thanks for your input, i'll look into all your suggestions.

I can't speak for jusasi, but in my case i simply bought the EQM35 because i wanted something lightweight to set up on location as i already have a EQ6-R fixed setup.

The EQM35 should be more suited for A than the EQ3 pro as it has a larger gear wheel.

What i also wil look into is the mounts worm drive backlash, i have tweakt my EQ6-R yesterday and i imagine the same is possible for the EQM35/EQ3

Edited by Miguel1983
  • Like 1
Link to post
Share on other sites

Hi Miguel, my experience is that setting up autoguiding parameters opens up a totally different can of worms. 

Hence I'd suggest that you try to assess the quality of your mount BEFORE you try to guide by:

Taking some unguided shots, measuring the backlash and the Periodic Error, testing the accuracy of the gotos and feeling by hand any roughness in the axes motion. 

Once you're aware of the mechanics, you can safely set up the guide system, but also in this case, I advise my friends to start with RA only, as this isn't impacted by backlash. 

Dec is always more tricky and if you have moderate backlash you can try the procedure above to avoid it. Yet, having already homed in the parameters with RA guiding, it should be easier. Try to avoid massive overcorrections in both axes, and good luck.

 

Edited by FaDG
Link to post
Share on other sites
3 minutes ago, FaDG said:

Hi Miguel, my experience is that setting up autoguiding parameters opens up a totally different can of worms. 

Hence I'd suggest that you try to assess the quality of your mount BEFORE you try to guide by:

Taking some unguided shots, measuring the backlash and the Periodic Error, testing the accuracy of the gotos and feeling by hand any roughness in the axes motion. 

Once you're aware of the mechanics, you can safely set up the guide system, but also in this case, I advise my friends to start with RA only, as this isn't impacted by backlash. 

Dec is always more tricky and if you have moderate backlash you can try the procedure above to avoid it. Yet, having already homed in the parameters with RA guiding, it should be easier. 

Try to avoid massive overcorrections in both axes, and good luck

 

Solid tips and that's what i'm going to do, first check the mount mechanically

i hope i'm not hijacking this tread to much, but im guessing the same is all to be applied to the EQ3 pro

Link to post
Share on other sites
On 31/03/2020 at 02:14, michael8554 said:

The GA run shows the mount has Periodic Error, that's why RA is heading south off scale, but 15arcsecs isn't bad actually.

If the OP mount has 15 arcsec of PE I would NEVER return it and rather have the backlash sorted out. 

It's an uncommonly good value for that class of mount: my HEQ5 has 23arcsec peak to peak and I'm just delighted with it 

Yet I suspect that Guiding Assistant was only exercised on part of the worm and the real PE will be higher, usually in the range of 80-100 arcsec for an EQ3. 

Yet it should be able to drive happily even with that, so the main issue seems to me the massive dec backlash. 

Link to post
Share on other sites
On 31/03/2020 at 01:39, jusasi said:

 

 

5nQgkif.png

.

 

K2RzEwn.png

 

One final word: your first two calibration figures and drive rates seem fine to me: I have seen mounts guiding seamlessly with results much worse than those. 

You may try to increase the guiding rate to 1x to increase mechanical reactiveness and reduce PHD2 aggressiveness in RA. this should tame the Dec backlash a bit, reducing the 58" to below 30. Buth this value is out of spec anyway: if confirmed you could contact the dealer asking them to optimised the worm gear block positioning. It's by no means indicating that the mount is faulty, just low care in assembly and quality check. But hey, you didn't purchase a 10 micron, did you? Manufacturers in china sadly don't waste too much time on QA. 

As for the different direction: did you perform a meridian flip between the two calibration runs? 

Keep up

Edited by FaDG
Link to post
Share on other sites

something else you might consider. had still some issues in my declination south movement since PEC-training only helps de RA-axis. i screwed open my gearbox of the declination. the motor was kinda worse off-setted installed and gears too. so i losen up the bolts a bit and with some fiddling i re-aligned the gear and motor in relation to the mount tested it all after. with mount, .. and looked trough my finderscope if i let the DEC-axe run. no more delay apparently. now waiting for clear kies to test it on the stars and guiding. 

 

the corrected one

93695740_218279162806869_6369620681050554368_n.jpg

 

the faulty one

93565828_606134616781261_8280906347818516480_n.jpg

Edited by Starfisher
Link to post
Share on other sites
  • 2 weeks later...
On 07/04/2020 at 07:38, Miguel1983 said:

Solid tips and that's what i'm going to do, first check the mount mechanically

i hope i'm not hijacking this tread to much, but im guessing the same is all to be applied to the EQ3 pro

i losen just a tick up my bolt of the Dec axis inside the mount just a tick. and moved the mount head slow left and right till i felt no more 'counterpressure' when going south. i calibrated my guiding and.... no more messages that my south movement was insufficient

Link to post
Share on other sites

From looking at your graph, I believe that this is due to #1 your ra and Dec aggression and #2 your min motion settings.

Run the guiding and lower the aggression till the curve has no sudden spikes. Also, based on your arc seconds per pixel I'd lower the min motion to 0.05 because the star is moving too much before it can make a correction.

Have you had any luck so far?

Hope this helps.

Link to post
Share on other sites
  • 2 weeks later...
On 31/03/2020 at 06:36, Miguel1983 said:

Hi, at first glance i see similar things i've encountered with my EQM35-pro.

I have this mount since January and tried to use 3 times now, i had invested is a pocked powerbox, a USB hub and a small laptop to make this my second lightweight imaging rig, boy was that disappointing.

The aim was to use EQMOD without the HC directly trough a eqdir cable.

Calibration wouldn't finish, or return a prompt of "unexpected value's" or "star didn't move enough" etc.

Tried to guide with the HC and with ST4 cable, so no eqmod involved, no luck.

Basically, a gave up, i don't need this with a new mount, now its sitting there gathering dust, conclusion for me is don't buy anything less than a heq5.

Someone way smarter than me would probably adjust the eqmod settings, but i wouldn't know where to start.

I should have just returned it to FLO, or at least contacted them, but with all that bad weather we had in january, february and first half of march i'just didn't find the courage to keep on testing/trying

 

I hope you get this sorted, i will follow along, maybe there's a solution here

Hi Miguel, I have a EQ3-pro synscan mount, and have tried autoguiding with PHD2. I think you are right to feel frustrated. I had problems to start with but have decided to work my way through them. Its likely your mount is not easy to guide straight out, so I don't know if you have experience of autoguiding and PHD with other systems.

At first, I could not get my guide camera to focus properly using the guide scope. I solved this problem, but then it was how to mount the autoguider. Then you have to learn PhD2. I think I will need to read the instructions. I have now getting the hang of EQMod to control my mount, but only after reading all the instructions and changing the settings on the EQMod - stepper values and worm gear values to match the mount.

Then you need to think about the weight of your optical train and if its too much for your mount. You probably know this, already.

All the best.

 

 

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.