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

astrophotography imaging
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#1 jusasi

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Posted 30 March 2020 - 04:59 PM

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

 

Continued on second post due to image limitations per post...


Edited by jusasi, 30 March 2020 - 05:02 PM.


#2 jusasi

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Posted 30 March 2020 - 05:00 PM

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. 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. belushi.gif

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.


Edited by jusasi, 30 March 2020 - 05:01 PM.


#3 bobzeq25

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Posted 30 March 2020 - 07:02 PM

A real problem here is that we don't have enough information.  What scope?  Describe the balcony, most are not stable enough for astrophotography.

 

But the bottom line is most likely to be that this is just not enough mount.  An EQ3 costs maybe $250?  My minimum recommendation for an astrophotography mount is the HEQ5Pro or the iOptron 30Pro.  Both about $1200.

 

Here's the problem.  It's completely unintuitive how precisely you have to track.  How good a mount you need to do this.  And what it costs to make a mount that good.

 

The good news about mounts is that you generally get what you pay for.  The bad news about mounts is that you generally get what you pay for.  <smile>

 

So, beginners often try to do astrophotography with an inadequate mount.  If your total budget is not at least $2000, you're best off starting with a camera, a lens, and a camera tracker.  Get things going with a 50mm lens, then try moving up.  Most of us find 200mm to be a good maximum with a tracker.  Long focal length magnifies tracking errors, a lot.

 

If it is something like $2000, half or more needs to go into the mount.

 

Minor point.  It's possible your EQ3 is particularly bad.  But even a good EQ3 is not really enough mount for this.  It bears almost no relationship to visual astronomy.


Edited by bobzeq25, 30 March 2020 - 07:04 PM.


#4 17.5Dob

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Posted 30 March 2020 - 07:24 PM

Looks completely normal for an EQ3......

If you need < 1" RMS, you need at least an EQ5... better yet an EQ6.



#5 Stelios

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Posted 30 March 2020 - 07:32 PM

In addition to mount quality, you have 100% aggression in RA with 1" exposures. This means that you are bouncing back-and-forth because of seeing. 

 

Drop RA aggression to 60% and increase exposure length to 2". Your RA should quiet down somewhat. 

 

If you can afford a HEQ5, get one. If not, learn to live with the EQ3 results. When I had a CG-5, I would get RMS around 2", which I think is possible with the EQ3 and a light load as well. With RMS of 2" you can still get round stars, although of course they'll be a bit bloated.



#6 georgian82

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Posted 31 March 2020 - 12:19 AM

I am not an expert in PHD2 guiding but just a few observations based on my own previous frustrations with guiding. Plus, this is the equipment that you currently have...

First, I would ditch the ST4 cable and go with ASCOM.

Second, I would set your exposure to around 2.5 seconds or so...you may have to play with this value but 1.0 second it’s too short and PHD2 is calling for too many corrections (hence the zigzagging of the graph).

Third, PHD2 has a predictive PEC option. Enable that and PHD2 will analyze your periodic error after a few cycles and apply a correction before it happens going forward.

Also, where in the sky are you pointing when calibrating? Are you balanced east heavy? Are you dithering? Maybe your settle time is not high enough or you have vibrations...are you using anti vibration pads?

Lastly, please make mention of your full equipment including guidescope and guiding camera..

Hope this helps

Edited by georgian82, 31 March 2020 - 12:30 AM.


#7 jusasi

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Posted 31 March 2020 - 01:56 AM

 

A real problem here is that we don't have enough information.  What scope?  Describe the balcony, most are not stable enough for astrophotography.

Of course, I got so focused on the issue that I forgot the basics! crazy.gif

 

- The balcony view is to NE-SE.

- 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.

- The platform is stable. I've taken plenty of great pictures using the AVX mount before, it's tried and tested.

 

 

 

In addition to mount quality, you have 100% aggression in RA with 1" exposures. This means that you are bouncing back-and-forth because of seeing.

 

Drop RA aggression to 60% and increase exposure length to 2". Your RA should quiet down somewhat.

The issue is that there's such a heavy drift with the mount that longer exposure times even seemed to worsen the result. It's always basically an overcorrection when it happens - often there's like 3 pulses to get the graph to change direction and when it does, it goes over the top immediately, creating a zig-zag. I normally prefer longer exposure times as they tend to smooth out the ride.

 

 

Also, where in the sky are you pointing when calibrating? Are you balanced east heavy? Are you dithering? Maybe your settle time is not high enough or you have vibrations...are you using anti vibration pads?

East. I've mentioned it, I've tried fully balanced, I've tried East biased, West biased, those did not seem to make a real difference. No dithering, I'm just focusing on testing the basic guiding before I even consider dithering. No anti-vibration pads, also shouldn't be vibrations, at least my AVX mount has no vibration issues.

 

Anyway, I bought this mount to be a lighter, more convenient travel mount that could just handle my 70mm travel scope. It is somewhat close to working, I have to admit, if only I could get the RA to calm down a bit, then I'd be looking at round stars. But looking at the PHD2 guide assistant graph, there seems to be something funky with RA - I mean, is it really normal for it to completely go off the rails like that?

 

 

Looks completely normal for an EQ3......

That's what I was a bit afraid of. Which makes me to ask the question: given that if I could throw ~1000€ to a travel mount, which needs to be somewhat light for plane travel, but accurate enough for round stars on this payload, what might it be?



#8 Huangdi

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Posted 31 March 2020 - 06:41 AM

That's what I was a bit afraid of. Which makes me to ask the question: given that if I could throw ~1000€ to a travel mount, which needs to be somewhat light for plane travel, but accurate enough for round stars on this payload, what might it be?


Explore Scientific iExos100 is your solution if it has to be portable.

I'm at over 7kg weight with counterweights (7kg is the suggested maximum payload) and I get 1.2-1.8" RMS, depending on seeing. That will b3 enough for your scope.

#9 RJF-Astro

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Posted 31 March 2020 - 07:58 AM

Your guiding graph looks very similar to when I am guiding my Star Adventurer (RA only). It does some nice bouncing as well, although I usually keep it below 3" total error. I do manage to get sharp subs up to 340mm (image scale 2.39 arcsecs per pixel).

 

Can you try polar aligning with polaris from another location? I would try that too to rule out PA-error. Sharpcap is nice, but I have had strange results when using it to polar align my star adventurer. A visual PA gave better results. I am sure it is user error, but it is a complicating factor.

 

Otherwise, a better mount will make your life easier.



#10 ConnorM

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Posted 31 March 2020 - 08:48 AM

I use an eq35 pro and it seems to be hit or miss most nights. I regularly shoot 180 second subs with my rokinon 135mm and ASI 178mm cool, but if I bump up to 300 seconds it gets much more hit or miss. My total error is typically less than 1 with a good polar alignment. The rokinon 135mm and 178mm has a smaller fov than my Meade 80mm /dslr combo and if I recall I was able to snag 300 second subs with that setup last time I used it. I really don't take any care when setting up guiding as everything is left on default settings. The phd2 will set a warning message saying it cannot make enough adjustments in Dec but it doesn't seem to throw the graph out too much and the subs seem fine even when doing some moderate pixel peeping.

I did have to get the entire mount head replaced a few months ago because the Dec motor and drive system kicked the bucket but I have not been nice to the Mount and was regularly imaging in -25 degree weather through the winter

#11 jusasi

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Posted 31 March 2020 - 09:20 AM

Well, it is a close call in the end, if can get the RA to behave a bit better with some PHD2 tweaks then it just might be enough. Then again, I wonder if the mount is just going to cause me more grief than joy in the long run. As noted on another forum, the Dec backlash alone on this particular unit is atrocious (58.072 seconds). Perhaps returning it and reconsidering more expensive options would simply be the best choice to make. undecided.gif



#12 klaussius

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Posted 31 March 2020 - 09:34 AM

The issue is that there's such a heavy drift with the mount that longer exposure times even seemed to worsen the result. It's always basically an overcorrection when it happens - often there's like 3 pulses to get the graph to change direction and when it does, it goes over the top immediately, creating a zig-zag. I normally prefer longer exposure times as they tend to smooth out the ride.

That's what lowering the aggression will improve. With lower aggression it won't overshoot that much.



#13 Huangdi

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Posted 31 March 2020 - 10:13 AM

Am I right to assume that you bought the eq3 pro synscan mount for 560 €?

Because if I am, that you could actually profit from selling it and buying an iExos100, which delivers far superior performance.

Pricing in this hobby can be so ridiculous 😂

Edited by Huangdi, 31 March 2020 - 10:14 AM.


#14 jusasi

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Posted 31 March 2020 - 10:36 AM

Am I right to assume that you bought the eq3 pro synscan mount for 560 €?

Because if I am, that you could actually profit from selling it and buying an iExos100, which delivers far superior performance.

Pricing in this hobby can be so ridiculous

You're correct.

 

I'm amazed how iExos100 can be a lot cheaper and yet superior - don't know what to believe anymore. The pricing seems to tell nothing. I also tried the iOptron SmartEQ Pro+ but that experiment ended rather quickly, as the build quality was absolutely horrendous, the look and feel was cheap and one of the plastic knobs actually crumbled in my hand and broke as I was mounting my scope on it. Back it went right after unboxing with all the little plastic bits and pieces... again should have read more reviews. Either that mount is just badly built and designed or the same faulty units just keep circulating around, either way, don't buy.



#15 Huangdi

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Posted 31 March 2020 - 02:05 PM

You're correct.

 

I'm amazed how iExos100 can be a lot cheaper and yet superior - don't know what to believe anymore. The pricing seems to tell nothing. I also tried the iOptron SmartEQ Pro+ but that experiment ended rather quickly, as the build quality was absolutely horrendous, the look and feel was cheap and one of the plastic knobs actually crumbled in my hand and broke as I was mounting my scope on it. Back it went right after unboxing with all the little plastic bits and pieces... again should have read more reviews. Either that mount is just badly built and designed or the same faulty units just keep circulating around, either way, don't buy.

Keep in mind, that the Skywatcher EQ X series has been in existence for many years, while the iExos100 is barely two years old and uses newer technology. In my opinion the belt-driven gears alone make it superior to any SW EQ Mount up to the NEQ5. 

 

Of course there are always the pro's and con's

 

There's just two things you have to watch out for when comparing them to other GEM's:

 

1. You don't have a handset (Which I hate anyway and which is totally unnecessary unless you insist on not having a computer with you)

2. There is no Polar scope (Once again, they're outdated and only useful if you don't have a computer)

 

If my mount had these accessories, I wouldn't use them. But some might want it...it's a drawback for those I guess. But since we're at the lowest budget there is, this is a great performer for its price.



#16 bobzeq25

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Posted 31 March 2020 - 03:21 PM

Of course, I got so focused on the issue that I forgot the basics! crazy.gif

 

- The balcony view is to NE-SE.

- 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.

- The platform is stable. I've taken plenty of great pictures using the AVX mount before, it's tried and tested.

 

The issue is that there's such a heavy drift with the mount that longer exposure times even seemed to worsen the result. It's always basically an overcorrection when it happens - often there's like 3 pulses to get the graph to change direction and when it does, it goes over the top immediately, creating a zig-zag. I normally prefer longer exposure times as they tend to smooth out the ride.

 

East. I've mentioned it, I've tried fully balanced, I've tried East biased, West biased, those did not seem to make a real difference. No dithering, I'm just focusing on testing the basic guiding before I even consider dithering. No anti-vibration pads, also shouldn't be vibrations, at least my AVX mount has no vibration issues.

 

Anyway, I bought this mount to be a lighter, more convenient travel mount that could just handle my 70mm travel scope. It is somewhat close to working, I have to admit, if only I could get the RA to calm down a bit, then I'd be looking at round stars. But looking at the PHD2 guide assistant graph, there seems to be something funky with RA - I mean, is it really normal for it to completely go off the rails like that?

 

That's what I was a bit afraid of. Which makes me to ask the question: given that if I could throw ~1000€ to a travel mount, which needs to be somewhat light for plane travel, but accurate enough for round stars on this payload, what might it be?

The obvious choice is a CEM25P.  Right price, right weight, right quality.  Both lighter and better performing than the twpical AVX.  Costs more, or course.  Note that along with the light weight comes a sensitivity to overly rough treatment.  Read the manual carefully before any use at all.  Follow it, especially the warnings.  Don't think you know better than the manufacturer.

 

In particular, assemble everything in place, don't let the light weight fool you into thinking it's OK to move the setup around assembled.

 

But, if you do some internet research, here or elsewhere, you'll find mostly good to excellent reviews.

 

The HEQ5Pro or iOptron 30Pro are sturdier, heavier, more expensive.

 

With 5 years of experience, and a lot of time on here carefully studying a number of people's experiences, I strongly disagree that mount pricing is ridiculous.  People want to believe in magic bargains, they don't exist.


Edited by bobzeq25, 31 March 2020 - 03:36 PM.


#17 zxx

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Posted 31 March 2020 - 07:02 PM

I get great results with my EQ3/C-G4 mount. I only have the drive kit not the full goto that has spur gears.

I would check the RA gears for binding. I also guide DEC in one direction.

Capture cg4.PNG


Edited by zxx, 31 March 2020 - 07:18 PM.



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