Possible defective unit #iEXOS-100 #TECHNICAL


Mario
 

Hi Paul, 

I was taking video of the moon and again noticed the oscillation you observed.
Again, this doesn't seem to be an issue with stars or DSO's but very noticeable with lunar or planetary observation.
Note, the tracking seems ok, the moon stays in frame and returns to essentially to the same spot after each oscillation.

I appreciate the explanations of how the motors are in constant motion....but how do we make this go away? 

Link to video here.

Regards,

Mario

On Thu, Sep 17, 2020 at 2:28 PM Paul via groups.io <paulw617=yahoo.com@groups.io> wrote:
Hello Wes and Harry,

Thank you for the quick response and for putting my mind at ease.

Paul


--
Regards,

Mario
Streetsville, Ontario

Mounts: iExos 100, Skyguider Pro
Scopes/Lenses: Main/Orion 80mm, DSLR/Tamron 18-400mm lens, guide/ZWO-340A
Computer: ASIAir
Cameras: Canon T2i DSLR, ZWO120MM (guide)
Utility Software: iPolar (for Skyguider polar alignment), iCap, Explorestars, Canon EOS Utility
Image Processing Software: Photoshop


Mario
 

Quick note, some others seem to be observing this same behaviour:

Appears here with lunar observation...link
This view of the iExos internals that seem to oscillate in time to what is being observed through the scope...link
Not sure if the second video is related bu seems to be....line the motor is pausing then 'catching up'

I would expect this motion to be smoothly tracking...not oscillating...


Regards,

Mario









On Fri, Oct 2, 2020 at 8:58 PM Mario via groups.io <mario1546=gmail.com@groups.io> wrote:
Hi Paul, 

I was taking video of the moon and again noticed the oscillation you observed.
Again, this doesn't seem to be an issue with stars or DSO's but very noticeable with lunar or planetary observation.
Note, the tracking seems ok, the moon stays in frame and returns to essentially to the same spot after each oscillation.

I appreciate the explanations of how the motors are in constant motion....but how do we make this go away? 

Link to video here.

Regards,

Mario

On Thu, Sep 17, 2020 at 2:28 PM Paul via groups.io <paulw617=yahoo.com@groups.io> wrote:
Hello Wes and Harry,

Thank you for the quick response and for putting my mind at ease.

Paul


--
Regards,

Mario
Streetsville, Ontario

Mounts: iExos 100, Skyguider Pro
Scopes/Lenses: Main/Orion 80mm, DSLR/Tamron 18-400mm lens, guide/ZWO-340A
Computer: ASIAir
Cameras: Canon T2i DSLR, ZWO120MM (guide)
Utility Software: iPolar (for Skyguider polar alignment), iCap, Explorestars, Canon EOS Utility
Image Processing Software: Photoshop


--
Regards,

Mario
Streetsville, Ontario

Mounts: iExos 100, Skyguider Pro
Scopes/Lenses: Main/Orion 80mm, DSLR/Tamron 18-400mm lens, guide/ZWO-340A
Computer: ASIAir
Cameras: Canon T2i DSLR, ZWO120MM (guide)
Utility Software: iPolar (for Skyguider polar alignment), iCap, Explorestars, Canon EOS Utility
Image Processing Software: Photoshop


Wes Mcdonald
 

Mario

Are you using explorestars?

If so are you in P or T mode?

Wes

--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Mario
 

Hi Wes, I'm using an ASIAir Pro in both Sidereal and Lunar tracking mode with the iExos connected via serial cable.
I'm not sure if that makes a difference or what others have been using when experiencing the problem. I could try and use Explorestars to see if the problem exists.

Regards,

Mario


On Fri, Oct 2, 2020 at 9:13 PM Wes Mcdonald <wesmcd6@...> wrote:
Mario

Are you using explorestars?

If so are you in P or T mode?

Wes

--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


--
Regards,

Mario
Streetsville, Ontario

Mounts: iExos 100, Skyguider Pro
Scopes/Lenses: Main/Orion 80mm, DSLR/Tamron 18-400mm lens, guide/ZWO-340A
Computer: ASIAir
Cameras: Canon T2i DSLR, ZWO120MM (guide)
Utility Software: iPolar (for Skyguider polar alignment), iCap, Explorestars, Canon EOS Utility
Image Processing Software: Photoshop


Wes Mcdonald
 

Mario

What does the asiair use to drive the pmc8?  Does it use the Es ascom driver?

Surging during lunar viewing makes no sense relative to the pmc8.  If the moon is moving in steps it is because the mount is being driven in steps.  This is how explorestars in Point mode does it.   But when you are using the ES driver and ascom the mount tracks smoothly at sidereal rate.   No surging.   

I believe you stated the surging is not present for stars.  In fact we all know it is not as our photos look great.  

I suggest to you the issue is with how the asiair is driving the mount.

Wes



--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


James Ball
 

Mine does the same thing whether it is using ExploreStars on the Android tablet or Ascom through a wired connection.  With the motor cover removed it will pulse like the second video as soon as it is unparked.  The pulse in the gears is in perfect time with the pulse sound heard from the electronics, just like the sound in the video Jennifer posted of the controller on her G8. 

With a 700mm FL scope and 25mm eyepiece you can't really see it, but with a 2000mm FL scope and 10mm eyepiece it is very evident.  It is definitely a start/stop motion in the drive motor.  Could Ascom be using the Point mode instead of Tracking mode for some reason?

As for the photography, it doesn't hurt the quality of the images when stacking an .avi file for planetary/lunar it might even help average out any dust specs on the sensor window.  I do think it is part of the problem when trying to get something like SharpCap Object Tracking to calibrate on high magnification work on planets.  I am not sure how to calculate the amplitude of the motion from the video clip, but I would imagine it is in the arc second or sub arc second range, which is probably not even noticeable in a normal guide scope used for AP.

For reference I use ASCOM 6.4 SP1-6.4.1.2695, PMC-Eight ASCOM driver revised 2019.01.07 Release Any CPU, SharpCap version 3.2.6392.0 7/28/2020, CdC Version 4.3 beta-4178-2b5ac26 2020/09/28 04:07:59  or current version of Explore Stars for Android and current newest firmware for the mount.

-- James Ball
Dawson Springs, Ky
Mounts: iEXOS-100
Scopes: Meade ETX90RA(deforked now) Sky Watcher 150MCT
Camera: ZWO ASI 120MC-S
Software: Explore Stars Android, ASCOM, Stellarium Scope, Stellarium, AS!3, SharpCap, RegiStax6.


Jerry Hubbell - Explore Scientific VP Engineering
 

On Fri, Oct 2, 2020 at 09:11 PM, Mario wrote:
Quick note, some others seem to be observing this same behaviour:
 
Appears here with lunar observation...link
This view of the iExos internals that seem to oscillate in time to what is being observed through the scope...link
Not sure if the second video is related bu seems to be....line the motor is pausing then 'catching up'
 
I would expect this motion to be smoothly tracking...not oscillating...
Hi Mario,

There is a documented 1.3 second oscillation in the motor driver chip which I have talked about previously ( https://espmc-eight.groups.io/g/MAIN/message/3894 ) as some of our customers identified on the G11. We identified this issue about 2 years ago but the magnitude of the problem is typically < 0.5 arc-second. In fact it has been demonstrated to be smaller than that as some users have reported an total RA guiding error ~ 0.5 arc-second including scintillation effects during long exposure imaging. This behavior does not affect long exposure imaging, nor lunar/planetary imaging at long focal lengths as the stacking software can manage the small amount of "jitter" caused by the motor driver. The only real observing that was impacted was visual observing at very high focal lengths typical when observing Mars, Jupiter, Saturn, etc.  Focal lengths of > 2500 mm when visually observing these planets were impacted.

At the time of discovery, after some investigation, we found that an increase in the motor current on the G11 helped to reduce this 1.3 second "jitter" significantly, although we also found that it depended on the equipment load and could be exacerbated by having weight at long moment arms which increased the inertial load. 

Based on your video, I made some measurements and assumed the following:

Video is a 1080p resolution image
The full width of the moon would effectively stretch the full width of the frame if centered
The width of the moon is 2160 km and 30 arc-minutes (1800 arc-second)
I measured the motion of the video using the crater Hell which is 33 km wide
I found that the oscillation (peak to peak) was about 1/2 the width of crater Hell, or about 15 km
The pixel scale for the image was about 2 km per pixel (2160/1080) or about 1.7 arc-seconds/pixel (1800/1080)
Based on this, the oscillation is equal to about (15 km / 2 km) * 1.7 arc-seconds which equals 12 arc-seconds peak to peak.

This is equal to about 2 arc-seconds RMS which is about 4 times what we would expect based on our previous experience.

It appears that there is something in your equipment configuration that could be aggravating the appearance of this tiny oscillation, perhaps the total load or how it is mounted.
If you could give me some details in that regard I would appreciate it. Also, it might be possible to increase the motor current setting to help mitigate this issue and reduce the 
magnitude of the oscillation.  

Again, it is important to realize that this motion is just one component of the motion you will see when observing the moon or planets at a large focal length either through the
eyepiece or via live video.  There is the natural drift in Declination, there is the local seeing conditions which can cause the motion to be at least the same magnitude or even more
than what you are seeing here.

Thanks for your report Mario.
 
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


Mario
 

First off, thank you for that detailed analysis Jerry, appreciated.
The old post was an interesting read, I appreciate the difficulty of making changes to the chip and it sounds like increasing the current to the motor might be an option.

The first video I attached was made with a Meade LX65 Cassegrain @ 1900mmFL x 127mm. I think I used a 25mm eyepiece and my trusty Celestron Neximage CCD at 720x480 @ 25 FPS. I may have used my 2x doubler but I don't recall for sure, sorry.
The iexos is on the latest firmware. Although I was managing the mount via the ASIAir, the camera was plugged directly into my laptop. I recall switching the ASIAir tracking mode between Sidereal and Lunar tracking to see if the issue would go away and it was present in both modes.

I can try and provide more information - just let me know what you need.

I agree with your comments; I don't notice the oscillation issue when imaging with my wider-field Orion 80x400mm refractor. The scope is over 30 years old and I'm still getting nice round stars and 2-3min guided exposures using the iExos. I could probably push it even longer and have similar success. To your point, I only notice the issue with the higher focal length LX65, narrower field of view with planetary/lunar viewing/video. 

The LX65 is about 6.2Lbs and I needed both counter-weights almost fully extended to balance the mount. I feel confident the balance was fairly good but find there's some friction with the mount when trying to balance so it's as good as I could get it. 
I also thought that the increased mass/inertia of the bigger scope and perhaps slight off-balance configuration might contribute to making a small issue have a bigger than normal impact visually.

My goal for that evening was to try and learn how to stack video to produce some nice pictures of the moon and perhaps Jupiter using this video-stacking technique when the oscillation became apparent.
We had already started this thread when I received the LX65 so I wasn't too worried if the issue should appear as others had indicated I could stack/process the issue away.

However, we were just viewing the Moon and Jupiter (and for that the long FL and magnification is required) and people were looking through the eyepiece and amazed at the clarity but then looked up and said, 'Why's it wobbling?'
I felt a little silly trying to explain it - lol.

It's like trying to explain why the radio doesn't work on your brand-new Ferrari - lol.
It still goes really fast but it's still annoying :)

I get this hobby is technical and has a learning curve and requires practice and tinkering - that's kinda why I like it. 
But I'm hoping we can get this sorted out.

@ Wes, i'm going to do some digging and see if I can determine what's driving the ASIAir (ASCOM or other) and what exactly happens between Sidereal and Lunar tracking - I don't see a 'Point'  mode for the ASIAir.
ZWO just released a new firmware version with a video mode so I'll see if this issue persists.  I'm aware we don't want to turn this into a third-party discussion but it seems others have noticed the issue with different non-ASI configurations.

Jerry, if there's a way to increase the current to the mount to minimize this, then I'm willing to try. Previous comments about power consumption when on battery noted.

Regards,

Mario



On Sat, Oct 3, 2020 at 11:05 AM Jerry Hubbell - Explore Scientific VP Engineering <jrh@...> wrote:
On Fri, Oct 2, 2020 at 09:11 PM, Mario wrote:
Quick note, some others seem to be observing this same behaviour:
 
Appears here with lunar observation...link
This view of the iExos internals that seem to oscillate in time to what is being observed through the scope...link
Not sure if the second video is related bu seems to be....line the motor is pausing then 'catching up'
 
I would expect this motion to be smoothly tracking...not oscillating...
Hi Mario,

There is a documented 1.3 second oscillation in the motor driver chip which I have talked about previously ( https://espmc-eight.groups.io/g/MAIN/message/3894 ) as some of our customers identified on the G11. We identified this issue about 2 years ago but the magnitude of the problem is typically < 0.5 arc-second. In fact it has been demonstrated to be smaller than that as some users have reported an total RA guiding error ~ 0.5 arc-second including scintillation effects during long exposure imaging. This behavior does not affect long exposure imaging, nor lunar/planetary imaging at long focal lengths as the stacking software can manage the small amount of "jitter" caused by the motor driver. The only real observing that was impacted was visual observing at very high focal lengths typical when observing Mars, Jupiter, Saturn, etc.  Focal lengths of > 2500 mm when visually observing these planets were impacted.

At the time of discovery, after some investigation, we found that an increase in the motor current on the G11 helped to reduce this 1.3 second "jitter" significantly, although we also found that it depended on the equipment load and could be exacerbated by having weight at long moment arms which increased the inertial load. 

Based on your video, I made some measurements and assumed the following:

Video is a 1080p resolution image
The full width of the moon would effectively stretch the full width of the frame if centered
The width of the moon is 2160 km and 30 arc-minutes (1800 arc-second)
I measured the motion of the video using the crater Hell which is 33 km wide
I found that the oscillation (peak to peak) was about 1/2 the width of crater Hell, or about 15 km
The pixel scale for the image was about 2 km per pixel (2160/1080) or about 1.7 arc-seconds/pixel (1800/1080)
Based on this, the oscillation is equal to about (15 km / 2 km) * 1.7 arc-seconds which equals 12 arc-seconds peak to peak.

This is equal to about 2 arc-seconds RMS which is about 4 times what we would expect based on our previous experience.

It appears that there is something in your equipment configuration that could be aggravating the appearance of this tiny oscillation, perhaps the total load or how it is mounted.
If you could give me some details in that regard I would appreciate it. Also, it might be possible to increase the motor current setting to help mitigate this issue and reduce the 
magnitude of the oscillation.  

Again, it is important to realize that this motion is just one component of the motion you will see when observing the moon or planets at a large focal length either through the
eyepiece or via live video.  There is the natural drift in Declination, there is the local seeing conditions which can cause the motion to be at least the same magnitude or even more
than what you are seeing here.

Thanks for your report Mario.
 
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


--
Regards,

Mario
Streetsville, Ontario

Mounts: iExos 100, Skyguider Pro
Scopes/Lenses: Main/Orion 80mm, DSLR/Tamron 18-400mm lens, guide/ZWO-340A
Computer: ASIAir
Cameras: Canon T2i DSLR, ZWO120MM (guide)
Utility Software: iPolar (for Skyguider polar alignment), iCap, Explorestars, Canon EOS Utility
Image Processing Software: Photoshop


Marko Pola
 

I have been doing planetary imaging on my exos2 and I experience the same rocking motion. It caught my attention when I noticed the sound of my motors had a rhythm that matched the rocking motion on the video. I am using an 8” SCT (2000mm FL) with a 2x Barlow. I also use the ASIAIR Pro. 


It’s mostly evident when I go into the 320x240 ROI mode on Mars. The planet fills most of that area but the rocking motion stays confined within that view so I am able to successfully record the video I need for stacking. The planet will slowly move out of the FOV even with the mount tracking so I use the manual controls to keep it centered while recording.  I just assumed that was due to my polar alignment that not being perfect. 


jusr thought I would include my experience with the wobble/rocking on my mount. 
--
Skill Level: Newbie learning astrophography
Mounts
: ES EXOS2 with PMC-8 
Scopes/Lenses: Canon 300mm F4, ES 10" F5 Truss Tube Dobsonian, Meade LX65 8” F10 ACF SCT
Cameras:  Canon EOS 650D T4i modified, Canon EOS 750D T6i unmodified, ZWO ASI120MC-S, ASI120MM Mini
Software: ASIAIR Pro, Still Learning the Ropes :)


James Ball
 

I don't think the amount of weight factors in too much as I first noticed the motion using the ETX90 where two counter weights at the very top of the bar will balance it. 

The second video Mario posted in his second post showing an allen wrench in the pulley is what I notice when just watching the small pulley, a stop start motion at the 1.3 second interval.  It never bothered me as I thought it was just the electronics sending pulses to move the motor in steps as it tracks, instead of a steady movement like you find in the old C8 synchro motors.  It definitely though does correspond to the sound of the electronics, the pulsing hiss that is heard as it is tracking. 
--
James Ball
Dawson Springs, Ky
Mounts: iEXOS-100
Scopes: Meade ETX90RA(deforked now) Sky Watcher 150MCT
Camera: ZWO ASI 120MC-S
Software: Explore Stars Android, ASCOM, Stellarium Scope, Stellarium, AS!3, SharpCap, RegiStax6.


Derrell Oliver
 

Hey Guys,
I just stumbled upon this Topic... My iEXOS-100 mount has always done this also, I have just gotten used to it I guess but
if there is a fix for it I sure would like to find out about it.
FYI, I control my mount via ASCOM wireless or more recently an ASCOM serial connection.
Seems like it would help on PHD2 Guiding, the best RMS Error I have seen is around 1.18" I attached a screen shot of one of my
last imaging sessions.
I would appreciate an info on this. 
--
Derrell Oliver

ES iEXOS-100 PMC-Eight with ES Heavy Duty ST3 tripod & Azimuth Adjuster
ES USB Power Bank
Astro-Tech AT80ED.
Astro-Tech 0.8 Field Flattener/Reducer.
Meade Infinity ST80 with Lunt Solar dual speed crayford focuser.
Meade Polaris 90 with GSO dual speed crayford focuser.
Meade Polaris 130 with ScopeStuff 1.25 crayford focuser.
ZWO ASI120mc-s, Canon XSi 450d.
ZWO ASI120mm-mini & ZWO 30mm f/4 Mini Guide Scope
EQ2 Mount with Orion EQ-2M RA Drive.
AZ3 Alt-Azimuth Mount.


Derrell Oliver
 

I forgot to add that I am using the ES ASCOM driver and the latest firmware update for my iEXOS-100 which increased 
the motor current when slewing but not while tracking, I do know that the goto results are excellent now !!
--
Derrell Oliver

ES iEXOS-100 PMC-Eight with ES Heavy Duty ST3 tripod & Azimuth Adjuster
ES USB Power Bank
Astro-Tech AT80ED.
Astro-Tech 0.8 Field Flattener/Reducer.
Meade Infinity ST80 with Lunt Solar dual speed crayford focuser.
Meade Polaris 90 with GSO dual speed crayford focuser.
Meade Polaris 130 with ScopeStuff 1.25 crayford focuser.
ZWO ASI120mc-s, Canon XSi 450d.
ZWO ASI120mm-mini & ZWO 30mm f/4 Mini Guide Scope
EQ2 Mount with Orion EQ-2M RA Drive.
AZ3 Alt-Azimuth Mount.