NGC5371 and surrounding galaxies


REDIGER-LIZLOV Didier
 

Link works ans vert nice field.

Didier REDIGER-LIZLOV

Le 2 juin 2020 23:14, "uncarollo2 <chris1011@...> via groups.io" <chris1011@...> a écrit :
Hi Astronuts,

I joined AstroBin and posted my first image. Hope the link works:
https://www.astrobin.com/full/vsz056/0/?nc=user

This is an image taken with the Mach2 and 160EDF refractor, unguided over a period of 2 hours. I modeled a path that the object would take with 3 data points and let MaximDL take a set of images until the scope ran out of room and stopped at the limit. I'm shooting in very light polluted skies, the Moon was up and bright, so i was pleased that i was able to record some very faint stuff.

No guide scope was used, no field flattener, just the 160 refractor straight to the 8300 chip. Larger chips would need a flattener of course.

Rolando


Worsel
 

Sebastien

The amount of drift, measured in arc-seconds per unit time, will depend only on the mount. How that drift appears in an image will be a function of the scope and camera.

Bryn


Roland Christen
 

I'm not into pixels, I'm more looking at allowable arc seconds. The skies some nights allow you to capture 3 arc sec FWHM, but on good nights you can get perhaps 1.5 arc sec FWHM. With a shorter scope you might only be able to get 4 arc sec FWHM on even the best of nights. So, the amount of allowable drift changes with the resolution capabilities of the scope and your local seeing conditions.

Rolando



-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, Jun 6, 2020 10:30 am
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

Focal length has nothing to do with how long to do unguided. Unguided depends on how well your model is made and how much drift you are willing to accept in your image. 

Rolando, I'm not sure I'm getting this right. I'm probably missing something about the modeling part here... Please enlighten me.

I thought the "amount of drift I'm willing to accept" was the amount of recorded signal (pixels) that is "offset" in the frame due to the mount's (in)ability to accurately track an object,(isn't it why we usually guide ?) which is also related to the image scale, which in turn relates to the focal length of the telescope...

So I'm not sure how two scopes with different focal lengths would lead to the same amount of drift in an unguided sub of the same exposure time (all other parameters being equal). Seems to me that the more focal length, the more drift (pixel offsets over time) I get, wether it's caused by PE (which I understand is not an issue with AE) or bad PA.

Sorry if my question seems silly, I'm a kind of "advanced newbie in astrophotography" as I like to call myself... 😉


Regards,

Sebastien


Sébastien Doré
 

Focal length has nothing to do with how long to do unguided. Unguided depends on how well your model is made and how much drift you are willing to accept in your image. 

Rolando, I'm not sure I'm getting this right. I'm probably missing something about the modeling part here... Please enlighten me.

I thought the "amount of drift I'm willing to accept" was the amount of recorded signal (pixels) that is "offset" in the frame due to the mount's (in)ability to accurately track an object,(isn't it why we usually guide ?) which is also related to the image scale, which in turn relates to the focal length of the telescope...

So I'm not sure how two scopes with different focal lengths would lead to the same amount of drift in an unguided sub of the same exposure time (all other parameters being equal). Seems to me that the more focal length, the more drift (pixel offsets over time) I get, wether it's caused by PE (which I understand is not an issue with AE) or bad PA.

Sorry if my question seems silly, I'm a kind of "advanced newbie in astrophotography" as I like to call myself... 😉


Regards,

Sebastien


J. Belden
 

Exactly what I expected.  Like the difference between a real Rolex watch vs a knockoff, you can see the micro stepping if you look close enough.

Joe


Roland Christen
 

About 90% of that drift rate is due to polar misalignment. Normally one would want to polar align a mount to have a Dec drift of 1 arc-sec per 5 minutes, or better.
The whole idea was to see in the extreme what the tracking accuracy could be with a simple model. Obviously you would not want to set up a mount this poorly to do imaging. A good polar scope alone could get you 10 times closer to the pole.

Rolando



-----Original Message-----
From: Brian Valente <bvalente@...>
To: main@ap-gto.groups.io
Sent: Fri, Jun 5, 2020 11:47 am
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

Any idea how much of that drift rate is due to polar misalignment vs other sources of RA drift (atmosphere, etc.)

On Fri, Jun 5, 2020 at 9:43 AM uncarollo2 <chris1011@...> via groups.io <chris1011=aol.com@groups.io> wrote:

just wondering up to how much focal length would the Mach2 be suitable unguided.
Focal length has nothing to do with how long to do unguided. Unguided depends on how well your model is made and how much drift you are willing to accept in your image. In the image that I posted the drift rate was approximately 5 arc sec per hour. Each 10 minute exposure had approximately 0.67 arc sec of drift, more or less. After stacking, the resulting stars had a value of .065 for flatness in MaximDL (see attachment below). Some of the exposures had more, some had less, and I simply stacked them all with Median Combine.

5 arc sec per hour might seem high, but the setup I used was purposely offset from the pole and had very high drift rate. Before modeling the RA drift was measured at 48 arc-sec/hr and the Dec was 96 arc-sec/hour. I would expect that one could get modeling down to +- 1 arc-sec/hour with good polar alignment.

Roland





-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io
Sent: Thu, Jun 4, 2020 10:40 pm
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

Interesting! Thanks for the 101 course on mount design tradeoffs Rolando.

Just wondering up to how much focal length would the Mach2 be suitable unguided. Do you think it would do it at say 1400mm FL (8in Edge+FR)? What about 2000mm (no reducer)?
Any feedback from the lucky folks that already got their hands on the Mach2?

Sebastien


--
Brian 



Brian Valente


Bill Long
 

The mirror on the SCT is usually the problem, or so I am told by those that have tested it out. I dont use SCT's. RC mirrors dont move though (neither do CDK mirrors) so those would be more suited to unguided imaging.

I shot unguided at 1720mm on the 1100 with AE and it worked wonderfully. I would not hesitate to do the same on the Mach 2 if I had one. That was on a iDK from AG Optical.


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Seb@stro <sebastiendore1@...>
Sent: Friday, June 5, 2020 9:45 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies
 
Hi Bill,

Not sure how an RC would be that much easier than an SCT unguided. Could you elaborate ? Are you talking about focusing, mirror flop, thermal equilibrium issues, else ? Note that I'm not familiar at all with RCs. 

That said, Rolando is getting pretty impressive unguided results with its 160EDF F/7 which I suppose at 1120mm FL since its " just the 160 refractor straight to the 8300 chip". 

Which makes me wondering if a 1400mm scope would be within reach of the Mach2 unguided in the first place.

Sebastien



De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Bill Long <bill@...>
Envoyé : 5 juin 2020 11:24
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] NGC5371 and surrounding galaxies
 
Unguided imaging with SCT's is a big challenge, unrelated to the mount. A similar sized RC would have no issues.


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Seb@stro <sebastiendore1@...>
Sent: Thursday, June 4, 2020 8:40 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies
 

Interesting! Thanks for the 101 course on mount design tradeoffs Rolando.

Just wondering up to how much focal length would the Mach2 be suitable unguided. Do you think it would do it at say 1400mm FL (8in Edge+FR)? What about 2000mm (no reducer)?

Any feedback from the lucky folks that already got their hands on the Mach2?

Sebastien



Sébastien Doré
 

Hi Bill,

Not sure how an RC would be that much easier than an SCT unguided. Could you elaborate ? Are you talking about focusing, mirror flop, thermal equilibrium issues, else ? Note that I'm not familiar at all with RCs. 

That said, Rolando is getting pretty impressive unguided results with its 160EDF F/7 which I suppose at 1120mm FL since its " just the 160 refractor straight to the 8300 chip". 

Which makes me wondering if a 1400mm scope would be within reach of the Mach2 unguided in the first place.

Sebastien



De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Bill Long <bill@...>
Envoyé : 5 juin 2020 11:24
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] NGC5371 and surrounding galaxies
 
Unguided imaging with SCT's is a big challenge, unrelated to the mount. A similar sized RC would have no issues.


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Seb@stro <sebastiendore1@...>
Sent: Thursday, June 4, 2020 8:40 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies
 

Interesting! Thanks for the 101 course on mount design tradeoffs Rolando.

Just wondering up to how much focal length would the Mach2 be suitable unguided. Do you think it would do it at say 1400mm FL (8in Edge+FR)? What about 2000mm (no reducer)?

Any feedback from the lucky folks that already got their hands on the Mach2?

Sebastien



 

Any idea how much of that drift rate is due to polar misalignment vs other sources of RA drift (atmosphere, etc.)


On Fri, Jun 5, 2020 at 9:43 AM uncarollo2 <chris1011@...> via groups.io <chris1011=aol.com@groups.io> wrote:

just wondering up to how much focal length would the Mach2 be suitable unguided.
Focal length has nothing to do with how long to do unguided. Unguided depends on how well your model is made and how much drift you are willing to accept in your image. In the image that I posted the drift rate was approximately 5 arc sec per hour. Each 10 minute exposure had approximately 0.67 arc sec of drift, more or less. After stacking, the resulting stars had a value of .065 for flatness in MaximDL (see attachment below). Some of the exposures had more, some had less, and I simply stacked them all with Median Combine.

5 arc sec per hour might seem high, but the setup I used was purposely offset from the pole and had very high drift rate. Before modeling the RA drift was measured at 48 arc-sec/hr and the Dec was 96 arc-sec/hour. I would expect that one could get modeling down to +- 1 arc-sec/hour with good polar alignment.

Roland





-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io
Sent: Thu, Jun 4, 2020 10:40 pm
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

Interesting! Thanks for the 101 course on mount design tradeoffs Rolando.

Just wondering up to how much focal length would the Mach2 be suitable unguided. Do you think it would do it at say 1400mm FL (8in Edge+FR)? What about 2000mm (no reducer)?
Any feedback from the lucky folks that already got their hands on the Mach2?

Sebastien



--
Brian 



Brian Valente


Roland Christen
 


just wondering up to how much focal length would the Mach2 be suitable unguided.
Focal length has nothing to do with how long to do unguided. Unguided depends on how well your model is made and how much drift you are willing to accept in your image. In the image that I posted the drift rate was approximately 5 arc sec per hour. Each 10 minute exposure had approximately 0.67 arc sec of drift, more or less. After stacking, the resulting stars had a value of .065 for flatness in MaximDL (see attachment below). Some of the exposures had more, some had less, and I simply stacked them all with Median Combine.

5 arc sec per hour might seem high, but the setup I used was purposely offset from the pole and had very high drift rate. Before modeling the RA drift was measured at 48 arc-sec/hr and the Dec was 96 arc-sec/hour. I would expect that one could get modeling down to +- 1 arc-sec/hour with good polar alignment.

Roland





-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io
Sent: Thu, Jun 4, 2020 10:40 pm
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

Interesting! Thanks for the 101 course on mount design tradeoffs Rolando.

Just wondering up to how much focal length would the Mach2 be suitable unguided. Do you think it would do it at say 1400mm FL (8in Edge+FR)? What about 2000mm (no reducer)?
Any feedback from the lucky folks that already got their hands on the Mach2?

Sebastien


Bill Long
 

Unguided imaging with SCT's is a big challenge, unrelated to the mount. A similar sized RC would have no issues.


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Seb@stro <sebastiendore1@...>
Sent: Thursday, June 4, 2020 8:40 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies
 

Interesting! Thanks for the 101 course on mount design tradeoffs Rolando.

Just wondering up to how much focal length would the Mach2 be suitable unguided. Do you think it would do it at say 1400mm FL (8in Edge+FR)? What about 2000mm (no reducer)?

Any feedback from the lucky folks that already got their hands on the Mach2?

Sebastien


Roland Christen
 

Ripple magnitude is pretty much fixed for a stepper motor in microstep mode. It has to do with the variation of position of the shaft during rotation. One way around the problem is to put a shaft encoder on the motor and use that to feed back the actual shaft rotation, similar to what is used on a DC servo. This adds large cost to the drive system and is used only on top end mounts.

Rolando

-----Original Message-----
From: David Fischer <dkn.fischer@...>
To: main@ap-gto.groups.io; David Fischer <dkn.fischer@...>
Sent: Thu, Jun 4, 2020 10:21 pm
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

So would the ripple magnitude depend fairly directly upon the details of step rate, motor step size, belt characteristics, motor holding strength ?
Is this the sort of thing that mount design engineers analyze at design time ?

-- David F.

On Thu, Jun 4, 2020 at 3:09 PM uncarollo2 <chris1011@...> via groups.io <chris1011=aol.com@groups.io> wrote:

yes please! i would like to see

Ok, see below. Sorry for the poor quality screen shots. I took them with my camera aimed at the screen ;^)).

Top image is the raw periodic error of a typical microstepper driving a precision worm. You might think the worm is not great, but the reality is that the two pulleys have runout and produce the majority of the large scale periodic error. The worm itself actually has only about 2 arc sec error. The rest is caused by the commercial pulleys which have a fair amount of runout. This is basically what you get in almost all imported non-encoder mounts that use belts and microsteppers.

The plot is taken at 100msec sample rate so you can see what is really happening during a typical worm cycle. Normally when you see a PE curve, the sample rate is 10 times slower, so you don't see the fast moving errors on PE data sheets.

The real issue is not the large scale PE, which can be handled by guiding (as long as it is slow moving and not too large an excursion). It is the fast moving errors at the 1 arc sec level that cause problems for guiders. The second plot shows in detail that microsteppers with belts have two fast moving errors. The belt teeth cause a ripple every few seconds (in this case once every 12 seconds at approx 1 arc sec P-P). If your guiding cadence is fast enough you might be able to guide it out successfully. However, if your guide rate approaches once every 3 - 4 seconds, you will see a residual error that modulates with time.

The faster moving error repeats every 2 seconds with another 1 arc-sec P-P error. This one cannot be easily guided out because the guider is always a step behind and can actually amplify this motion. The error is caused by the stepper motor itself which has 5% angle variation for each winding step point. If your camera pixel scale is 2 - 4 arc sec per pixel, you may not see these kinds of errors. If your guider is exposing at 2 - 3 seconds, the guide graph will average out the tiny fast motions and will record perhaps very low rms values. However, the stars that you are recording on your imaging camera are doing this tiny back and forth dance in RA and slightly smearing the resolution of your image.

The third graph below shows how the absolute encoder tames all three errors.







Sébastien Doré
 

Interesting! Thanks for the 101 course on mount design tradeoffs Rolando.

Just wondering up to how much focal length would the Mach2 be suitable unguided. Do you think it would do it at say 1400mm FL (8in Edge+FR)? What about 2000mm (no reducer)?

Any feedback from the lucky folks that already got their hands on the Mach2?

Sebastien


David Fischer
 

So would the ripple magnitude depend fairly directly upon the details of step rate, motor step size, belt characteristics, motor holding strength ?
Is this the sort of thing that mount design engineers analyze at design time ?

-- David F.


On Thu, Jun 4, 2020 at 3:09 PM uncarollo2 <chris1011@...> via groups.io <chris1011=aol.com@groups.io> wrote:

yes please! i would like to see

Ok, see below. Sorry for the poor quality screen shots. I took them with my camera aimed at the screen ;^)).

Top image is the raw periodic error of a typical microstepper driving a precision worm. You might think the worm is not great, but the reality is that the two pulleys have runout and produce the majority of the large scale periodic error. The worm itself actually has only about 2 arc sec error. The rest is caused by the commercial pulleys which have a fair amount of runout. This is basically what you get in almost all imported non-encoder mounts that use belts and microsteppers.

The plot is taken at 100msec sample rate so you can see what is really happening during a typical worm cycle. Normally when you see a PE curve, the sample rate is 10 times slower, so you don't see the fast moving errors on PE data sheets.

The real issue is not the large scale PE, which can be handled by guiding (as long as it is slow moving and not too large an excursion). It is the fast moving errors at the 1 arc sec level that cause problems for guiders. The second plot shows in detail that microsteppers with belts have two fast moving errors. The belt teeth cause a ripple every few seconds (in this case once every 12 seconds at approx 1 arc sec P-P). If your guiding cadence is fast enough you might be able to guide it out successfully. However, if your guide rate approaches once every 3 - 4 seconds, you will see a residual error that modulates with time.

The faster moving error repeats every 2 seconds with another 1 arc-sec P-P error. This one cannot be easily guided out because the guider is always a step behind and can actually amplify this motion. The error is caused by the stepper motor itself which has 5% angle variation for each winding step point. If your camera pixel scale is 2 - 4 arc sec per pixel, you may not see these kinds of errors. If your guider is exposing at 2 - 3 seconds, the guide graph will average out the tiny fast motions and will record perhaps very low rms values. However, the stars that you are recording on your imaging camera are doing this tiny back and forth dance in RA and slightly smearing the resolution of your image.

The third graph below shows how the absolute encoder tames all three errors.







Roland Christen
 


yes please! i would like to see

Ok, see below. Sorry for the poor quality screen shots. I took them with my camera aimed at the screen ;^)).

Top image is the raw periodic error of a typical microstepper driving a precision worm. You might think the worm is not great, but the reality is that the two pulleys have runout and produce the majority of the large scale periodic error. The worm itself actually has only about 2 arc sec error. The rest is caused by the commercial pulleys which have a fair amount of runout. This is basically what you get in almost all imported non-encoder mounts that use belts and microsteppers.

The plot is taken at 100msec sample rate so you can see what is really happening during a typical worm cycle. Normally when you see a PE curve, the sample rate is 10 times slower, so you don't see the fast moving errors on PE data sheets.

The real issue is not the large scale PE, which can be handled by guiding (as long as it is slow moving and not too large an excursion). It is the fast moving errors at the 1 arc sec level that cause problems for guiders. The second plot shows in detail that microsteppers with belts have two fast moving errors. The belt teeth cause a ripple every few seconds (in this case once every 12 seconds at approx 1 arc sec P-P). If your guiding cadence is fast enough you might be able to guide it out successfully. However, if your guide rate approaches once every 3 - 4 seconds, you will see a residual error that modulates with time.

The faster moving error repeats every 2 seconds with another 1 arc-sec P-P error. This one cannot be easily guided out because the guider is always a step behind and can actually amplify this motion. The error is caused by the stepper motor itself which has 5% angle variation for each winding step point. If your camera pixel scale is 2 - 4 arc sec per pixel, you may not see these kinds of errors. If your guider is exposing at 2 - 3 seconds, the guide graph will average out the tiny fast motions and will record perhaps very low rms values. However, the stars that you are recording on your imaging camera are doing this tiny back and forth dance in RA and slightly smearing the resolution of your image.

The third graph below shows how the absolute encoder tames all three errors.







DFisch
 

Rolando, thanks for the instruction.  i have an 1100 mount and lost the step in my thinking where disengaging the clutches loses the encoder feedback as to where they are constructed and installed on the mount.  When i was imagining "no lost position” with an upgrade to my already excellent 1100 to AE i forgot the fundamental difference of the new design.  no harm in dreaming.   i love your analogic comparison of the difference in the type of “noise” generated by the two types of drive systems. The differences in the mach2 with AE vs. 1100 AE wont be lost on me again.  Tom 

On Jun 4, 2020, at 4:46 PM, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:

The 1100 AE is more accurate, heavier construction, larger gearwheel and has hollow axes so you can run your own cables. Although it has clutches, the mount will not keep track of pointing while they are loose and you move the scope manually.

The 1100 has precision spur gear reduction and high speed servo motors, not belts and microsteppers. Belts and microsteppers are only accurate to arc sec levels when combined with absolute encoders on the shafts. Precision spur gears and Swiss servo motors can provide smooth arc sec level tracking, without AE, when you have a good PE correction curve.

Speaking of inexpensive mounts with steppers and belt drives:
Microsteppers with belts are audibly quiet but mechanically noisy (precision gears are audibly noisy but mechanically smooth). Have you ever seen what the periodic error looks like with a microstepper running a belt drive? Do you think it is smooth and accurate? Would you like to see?

Rolando



-----Original Message-----
From: DFisch <manusfisch@...>
To: main@ap-gto.groups.io
Sent: Sun, May 31, 2020 2:49 am
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

Rolando, how many of these features would be available to the 1100 after AE upgrade (notwithstanding the mechanical features).  How close would the similarities be on guiding and modeling .  Tom

On Jun 4, 2020, at 2:58 PM, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:

Besides the encoders eliminating PE, the Mach2 brings the ability to move the mount manually during visual sweeping of the skies without losing position. It also allows critical balance to be achieved without backing the worm off the wormwheel and possibly damaging the worm teeth in the process, if done wrong. The base of the mount has been widened for better stability. Internally the heavy shaft sits farther between the bearings for increased stability over the Mach1.

The absolute encoders are mapped so that the precision tracking and pointing is maintained over the entire 360 degree axis motion. Relative encoders can theoretically eliminate PE, but generally introduce sub-divisional error (SDE). Relative encoders cannot be mapped at the factory against a known standard lab encoder since they do not have individual distinct position information. So the tracking accuracy may contain no periodic error component, but will inevitably have large drift component due to encoder disc runout. The Renishaw RESA encoder system has some 64 million distinct positions which are carefully mapped in our initial test and setup routine here at AP. The data is then transferred to the CP5 where it is stored and used to provide precise tracking and positioning to the axes at every point in the rotation of the axes.

To sum up the Mach2:

Mount has clutches that allow precise balancing of the axes.

Clutches can be loosened for manual sweeping of the mount during visual observing with no loss of position.

The gearbox uses belt drive for quiet operation along with brushless microstepper motors

The motors are oversized to provide high torque, the belts are heavy duty.

Precision Absolute encoders eliminate periodic error during sidereal or custom tracking

The encoders are mapped over 360 degrees to provide precise positioning and tracking over the entire rotation

The mount base has been strengthened for lower vibration and better damping of heavy loads.

Modern feed-forward encoder control loop produces quick response to external forces and produces a stiffer mount

Both axes can be driven accurately at custom and variable rates for unguided imaging with modeling

Rolando






-----Original Message-----
From: willsonjared via groups.io <willsonjared@...>
To: main@ap-gto.groups.io
Sent: Thu, Jun 4, 2020 1:05 pm
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

For me, this feature will be the difference between a Mach2 being, “cool, but don’t really see a reason to upgrade from my Mach1” and being, “Wow, that would make it easy to bring a system into the field without needing to guide!”  Well done.  I can now see myself replacing my Mach1 at some point in the future which is something I couldn’t have imagined when the Mach2 was announced.



Bill Long
 

+1 for this. Sounds interesting. 🙂 


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Brian Valente <bvalente@...>
Sent: Thursday, June 4, 2020 1:51 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies
 
>> Have you ever seen what the periodic error looks like with a microstepper running a belt drive? Do you think it is smooth and accurate? Would you like to see?

yes please! i would like to see

On Thu, Jun 4, 2020 at 1:46 PM uncarollo2 <chris1011@...> via groups.io <chris1011=aol.com@groups.io> wrote:
The 1100 AE is more accurate, heavier construction, larger gearwheel and has hollow axes so you can run your own cables. Although it has clutches, the mount will not keep track of pointing while they are loose and you move the scope manually.

The 1100 has precision spur gear reduction and high speed servo motors, not belts and microsteppers. Belts and microsteppers are only accurate to arc sec levels when combined with absolute encoders on the shafts. Precision spur gears and Swiss servo motors can provide smooth arc sec level tracking, without AE, when you have a good PE correction curve.

Speaking of inexpensive mounts with steppers and belt drives:
Microsteppers with belts are audibly quiet but mechanically noisy (precision gears are audibly noisy but mechanically smooth). Have you ever seen what the periodic error looks like with a microstepper running a belt drive? Do you think it is smooth and accurate? Would you like to see?

Rolando



-----Original Message-----
From: DFisch <manusfisch@...>
To: main@ap-gto.groups.io
Sent: Sun, May 31, 2020 2:49 am
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

Rolando, how many of these features would be available to the 1100 after AE upgrade (notwithstanding the mechanical features).  How close would the similarities be on guiding and modeling .  Tom

On Jun 4, 2020, at 2:58 PM, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:

Besides the encoders eliminating PE, the Mach2 brings the ability to move the mount manually during visual sweeping of the skies without losing position. It also allows critical balance to be achieved without backing the worm off the wormwheel and possibly damaging the worm teeth in the process, if done wrong. The base of the mount has been widened for better stability. Internally the heavy shaft sits farther between the bearings for increased stability over the Mach1.

The absolute encoders are mapped so that the precision tracking and pointing is maintained over the entire 360 degree axis motion. Relative encoders can theoretically eliminate PE, but generally introduce sub-divisional error (SDE). Relative encoders cannot be mapped at the factory against a known standard lab encoder since they do not have individual distinct position information. So the tracking accuracy may contain no periodic error component, but will inevitably have large drift component due to encoder disc runout. The Renishaw RESA encoder system has some 64 million distinct positions which are carefully mapped in our initial test and setup routine here at AP. The data is then transferred to the CP5 where it is stored and used to provide precise tracking and positioning to the axes at every point in the rotation of the axes.

To sum up the Mach2:

Mount has clutches that allow precise balancing of the axes.

Clutches can be loosened for manual sweeping of the mount during visual observing with no loss of position.

The gearbox uses belt drive for quiet operation along with brushless microstepper motors

The motors are oversized to provide high torque, the belts are heavy duty.

Precision Absolute encoders eliminate periodic error during sidereal or custom tracking

The encoders are mapped over 360 degrees to provide precise positioning and tracking over the entire rotation

The mount base has been strengthened for lower vibration and better damping of heavy loads.

Modern feed-forward encoder control loop produces quick response to external forces and produces a stiffer mount

Both axes can be driven accurately at custom and variable rates for unguided imaging with modeling

Rolando






-----Original Message-----
From: willsonjared via groups.io <willsonjared@...>
To: main@ap-gto.groups.io
Sent: Thu, Jun 4, 2020 1:05 pm
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

For me, this feature will be the difference between a Mach2 being, “cool, but don’t really see a reason to upgrade from my Mach1” and being, “Wow, that would make it easy to bring a system into the field without needing to guide!”  Well done.  I can now see myself replacing my Mach1 at some point in the future which is something I couldn’t have imagined when the Mach2 was announced.



--
Brian 



Brian Valente


 

>> Have you ever seen what the periodic error looks like with a microstepper running a belt drive? Do you think it is smooth and accurate? Would you like to see?

yes please! i would like to see

On Thu, Jun 4, 2020 at 1:46 PM uncarollo2 <chris1011@...> via groups.io <chris1011=aol.com@groups.io> wrote:
The 1100 AE is more accurate, heavier construction, larger gearwheel and has hollow axes so you can run your own cables. Although it has clutches, the mount will not keep track of pointing while they are loose and you move the scope manually.

The 1100 has precision spur gear reduction and high speed servo motors, not belts and microsteppers. Belts and microsteppers are only accurate to arc sec levels when combined with absolute encoders on the shafts. Precision spur gears and Swiss servo motors can provide smooth arc sec level tracking, without AE, when you have a good PE correction curve.

Speaking of inexpensive mounts with steppers and belt drives:
Microsteppers with belts are audibly quiet but mechanically noisy (precision gears are audibly noisy but mechanically smooth). Have you ever seen what the periodic error looks like with a microstepper running a belt drive? Do you think it is smooth and accurate? Would you like to see?

Rolando



-----Original Message-----
From: DFisch <manusfisch@...>
To: main@ap-gto.groups.io
Sent: Sun, May 31, 2020 2:49 am
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

Rolando, how many of these features would be available to the 1100 after AE upgrade (notwithstanding the mechanical features).  How close would the similarities be on guiding and modeling .  Tom

On Jun 4, 2020, at 2:58 PM, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:

Besides the encoders eliminating PE, the Mach2 brings the ability to move the mount manually during visual sweeping of the skies without losing position. It also allows critical balance to be achieved without backing the worm off the wormwheel and possibly damaging the worm teeth in the process, if done wrong. The base of the mount has been widened for better stability. Internally the heavy shaft sits farther between the bearings for increased stability over the Mach1.

The absolute encoders are mapped so that the precision tracking and pointing is maintained over the entire 360 degree axis motion. Relative encoders can theoretically eliminate PE, but generally introduce sub-divisional error (SDE). Relative encoders cannot be mapped at the factory against a known standard lab encoder since they do not have individual distinct position information. So the tracking accuracy may contain no periodic error component, but will inevitably have large drift component due to encoder disc runout. The Renishaw RESA encoder system has some 64 million distinct positions which are carefully mapped in our initial test and setup routine here at AP. The data is then transferred to the CP5 where it is stored and used to provide precise tracking and positioning to the axes at every point in the rotation of the axes.

To sum up the Mach2:

Mount has clutches that allow precise balancing of the axes.

Clutches can be loosened for manual sweeping of the mount during visual observing with no loss of position.

The gearbox uses belt drive for quiet operation along with brushless microstepper motors

The motors are oversized to provide high torque, the belts are heavy duty.

Precision Absolute encoders eliminate periodic error during sidereal or custom tracking

The encoders are mapped over 360 degrees to provide precise positioning and tracking over the entire rotation

The mount base has been strengthened for lower vibration and better damping of heavy loads.

Modern feed-forward encoder control loop produces quick response to external forces and produces a stiffer mount

Both axes can be driven accurately at custom and variable rates for unguided imaging with modeling

Rolando






-----Original Message-----
From: willsonjared via groups.io <willsonjared@...>
To: main@ap-gto.groups.io
Sent: Thu, Jun 4, 2020 1:05 pm
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

For me, this feature will be the difference between a Mach2 being, “cool, but don’t really see a reason to upgrade from my Mach1” and being, “Wow, that would make it easy to bring a system into the field without needing to guide!”  Well done.  I can now see myself replacing my Mach1 at some point in the future which is something I couldn’t have imagined when the Mach2 was announced.



--
Brian 



Brian Valente


Roland Christen
 

The 1100 AE is more accurate, heavier construction, larger gearwheel and has hollow axes so you can run your own cables. Although it has clutches, the mount will not keep track of pointing while they are loose and you move the scope manually.

The 1100 has precision spur gear reduction and high speed servo motors, not belts and microsteppers. Belts and microsteppers are only accurate to arc sec levels when combined with absolute encoders on the shafts. Precision spur gears and Swiss servo motors can provide smooth arc sec level tracking, without AE, when you have a good PE correction curve.

Speaking of inexpensive mounts with steppers and belt drives:
Microsteppers with belts are audibly quiet but mechanically noisy (precision gears are audibly noisy but mechanically smooth). Have you ever seen what the periodic error looks like with a microstepper running a belt drive? Do you think it is smooth and accurate? Would you like to see?

Rolando



-----Original Message-----
From: DFisch <manusfisch@...>
To: main@ap-gto.groups.io
Sent: Sun, May 31, 2020 2:49 am
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

Rolando, how many of these features would be available to the 1100 after AE upgrade (notwithstanding the mechanical features).  How close would the similarities be on guiding and modeling .  Tom

On Jun 4, 2020, at 2:58 PM, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:

Besides the encoders eliminating PE, the Mach2 brings the ability to move the mount manually during visual sweeping of the skies without losing position. It also allows critical balance to be achieved without backing the worm off the wormwheel and possibly damaging the worm teeth in the process, if done wrong. The base of the mount has been widened for better stability. Internally the heavy shaft sits farther between the bearings for increased stability over the Mach1.

The absolute encoders are mapped so that the precision tracking and pointing is maintained over the entire 360 degree axis motion. Relative encoders can theoretically eliminate PE, but generally introduce sub-divisional error (SDE). Relative encoders cannot be mapped at the factory against a known standard lab encoder since they do not have individual distinct position information. So the tracking accuracy may contain no periodic error component, but will inevitably have large drift component due to encoder disc runout. The Renishaw RESA encoder system has some 64 million distinct positions which are carefully mapped in our initial test and setup routine here at AP. The data is then transferred to the CP5 where it is stored and used to provide precise tracking and positioning to the axes at every point in the rotation of the axes.

To sum up the Mach2:

Mount has clutches that allow precise balancing of the axes.

Clutches can be loosened for manual sweeping of the mount during visual observing with no loss of position.

The gearbox uses belt drive for quiet operation along with brushless microstepper motors

The motors are oversized to provide high torque, the belts are heavy duty.

Precision Absolute encoders eliminate periodic error during sidereal or custom tracking

The encoders are mapped over 360 degrees to provide precise positioning and tracking over the entire rotation

The mount base has been strengthened for lower vibration and better damping of heavy loads.

Modern feed-forward encoder control loop produces quick response to external forces and produces a stiffer mount

Both axes can be driven accurately at custom and variable rates for unguided imaging with modeling

Rolando






-----Original Message-----
From: willsonjared via groups.io <willsonjared@...>
To: main@ap-gto.groups.io
Sent: Thu, Jun 4, 2020 1:05 pm
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

For me, this feature will be the difference between a Mach2 being, “cool, but don’t really see a reason to upgrade from my Mach1” and being, “Wow, that would make it easy to bring a system into the field without needing to guide!”  Well done.  I can now see myself replacing my Mach1 at some point in the future which is something I couldn’t have imagined when the Mach2 was announced.


DFisch
 

Rolando, how many of these features would be available to the 1100 after AE upgrade (notwithstanding the mechanical features).  How close would the similarities be on guiding and modeling .  Tom

On Jun 4, 2020, at 2:58 PM, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:

Besides the encoders eliminating PE, the Mach2 brings the ability to move the mount manually during visual sweeping of the skies without losing position. It also allows critical balance to be achieved without backing the worm off the wormwheel and possibly damaging the worm teeth in the process, if done wrong. The base of the mount has been widened for better stability. Internally the heavy shaft sits farther between the bearings for increased stability over the Mach1.

The absolute encoders are mapped so that the precision tracking and pointing is maintained over the entire 360 degree axis motion. Relative encoders can theoretically eliminate PE, but generally introduce sub-divisional error (SDE). Relative encoders cannot be mapped at the factory against a known standard lab encoder since they do not have individual distinct position information. So the tracking accuracy may contain no periodic error component, but will inevitably have large drift component due to encoder disc runout. The Renishaw RESA encoder system has some 64 million distinct positions which are carefully mapped in our initial test and setup routine here at AP. The data is then transferred to the CP5 where it is stored and used to provide precise tracking and positioning to the axes at every point in the rotation of the axes.

To sum up the Mach2:

Mount has clutches that allow precise balancing of the axes.

Clutches can be loosened for manual sweeping of the mount during visual observing with no loss of position.

The gearbox uses belt drive for quiet operation along with brushless microstepper motors

The motors are oversized to provide high torque, the belts are heavy duty.

Precision Absolute encoders eliminate periodic error during sidereal or custom tracking

The encoders are mapped over 360 degrees to provide precise positioning and tracking over the entire rotation

The mount base has been strengthened for lower vibration and better damping of heavy loads.

Modern feed-forward encoder control loop produces quick response to external forces and produces a stiffer mount

Both axes can be driven accurately at custom and variable rates for unguided imaging with modeling

Rolando






-----Original Message-----
From: willsonjared via groups.io <willsonjared@...>
To: main@ap-gto.groups.io
Sent: Thu, Jun 4, 2020 1:05 pm
Subject: Re: [ap-gto] NGC5371 and surrounding galaxies

For me, this feature will be the difference between a Mach2 being, “cool, but don’t really see a reason to upgrade from my Mach1” and being, “Wow, that would make it easy to bring a system into the field without needing to guide!”  Well done.  I can now see myself replacing my Mach1 at some point in the future which is something I couldn’t have imagined when the Mach2 was announced.