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Which mounts have encoders?

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#1 robininni

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Posted 19 June 2017 - 02:00 PM

I know the HDX-110 does.  I think Paramount varieties do?  Could anyone list the popular mounts that do?

 

Thanks.



#2 havasman

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Posted 19 June 2017 - 02:42 PM

Any electronic push-to or go-to mount will have some type of encoders. Most modern mounts can be configured to include encoders. Most mounts that include encoders can be modified to a different encoder configuration.

 

The list of current production mounts without encoders is likely shorter than the list of those that include them.



#3 robininni

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Posted 19 June 2017 - 03:16 PM

I am looking for mounts (GEM) that allow you to unlock the clutches and move the mount and the mount not lose alignment.  I don't think that is super common, is it?  I know my Atlas mount won't do that.



#4 lambermo

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Posted 19 June 2017 - 03:17 PM

The awesome 10 Micron mounts have absolute encoders.

See http://www.10micron.eu/en/homepage/ for their mounts.

And http://www.10micron....ron-technology/ has a tab on their absolute encoders and what it does for unguided tracking.

-- Hans



#5 Ares69

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Posted 19 June 2017 - 03:18 PM

I am looking for mounts (GEM) that allow you to unlock the clutches and move the mount and the mount not lose alignment.  I don't think that is super common, is it?  I know my Atlas mount won't do that.

10Micron... the GM1000HPS has absolute encoders and will allow you to do that

They don't come cheap


Edited by Ares69, 19 June 2017 - 03:32 PM.


#6 Stelios

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Posted 19 June 2017 - 03:22 PM

I think you need absolute encoders for that. 10Micron has them, and you can buy them (at $6K IIRC) for Astro-Physics mounts.

 

On more regular Astro-Physics mounts, you can loosen clutches, move mount to wherever. Then you can tighten clutches (mount resumes tracking) and enter the coordinates of the object you are looking at in APCC (possibly other software too) and Sync. At that point, alignment is back on. But you *do* need to tell it what it's looking at.

 

I am also curious as to which other mounts have them, although it's not a feature I personally would be likely to use (why not just GoTo, using a planetarium program?)



#7 bobzeq25

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Posted 19 June 2017 - 03:27 PM

Some of the newer Atlas/clones will do that.  Look for models with "dual encoders".  Not to be confused with "precision encoders".


Edited by bobzeq25, 19 June 2017 - 03:28 PM.


#8 Tapio

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Posted 19 June 2017 - 03:31 PM

Skywatcher EQ8 and I believe AllView Mount too.

#9 photoracer18

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Posted 19 June 2017 - 03:43 PM

There are encoders and then there are encoders. Absolute encoders are different than motor encoders. Motor encoders will lose track of your sky location if you move the mount without using the motor/encoder combo (most go-to mounts). Absolute encoders never lose track of where you are (generally higher end mounts). Generally absolute encoders can be either an auxiliary set of axis encoders the mount electronics can access or a system that has no encoders on the motors themselves, just axis encoders.
Think of an absolute encoder mount as one that can be used go-to or push-to at the same time. An absolute encoder mount would not need to have the alignment rechecked every time if it was permanently mounted especially if you have to park the scope in a particular orientation to close the roof. As long as you left the mount running while you unlocked the axis to move the payload to a home position. If the mount has some kind of standby power mode that keeps track you would not even have to do that.
Losmandy Gemini 1 can do that because I have one (G11 G1). I assume the Gemini 2 can also. Mine actually has that and GPS and that is the way I got it. I see a lot of people who sell their encoders when they upgrade to go-to when they actually might be better off keeping them mounted (and sell off just the computer). Not quite as useful if you use you mount in the field one night at a time mostly, but could be useful at a week long star-party.

Edited by photoracer18, 19 June 2017 - 03:45 PM.

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#10 WadeH237

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Posted 19 June 2017 - 04:21 PM

There are many uses of the term "encoders" and I think that there is some confusion in the thread.

 

As has been said, pretty much every goto or push-to mount has encoders.  They are a necessity for these features to work.

 

Beyond that, encoders have a resolution, and they can be absolute or relative.

 

Low resolution encoders are sufficient for goto or push-to.  I think that a lot of mounts have around 4000 ticks, and this is plenty for that.  When people say that most mounts have encoders, these low resolution encoders are cheap and plentiful.

 

High resolution encoders are a completely different beast.  These things have many millions of ticks, and can detect motion on an axis in small fractions of an arc second.  These are good enough that you can do away with periodic error, backlash, etc.  They're found on the high end mounts like Paramout, ASA and 10Micron.  Astro-Physics offers them as an option.  They are generally very expensive (thousands of dollars).  10Micron is a special case here because they don't use off the shelf encoders.  They have a proprietary encoder and I don't believe that they publish the specs.  The results speak for themselves, and they work very well, though.

 

The difference between absolute and relative encoders is that absolute encoders can uniquely identify each tick, so they need no initialization or indexing.  Relative encoders can count ticks, but they need to be initialized to an index position.

 

Note that whether an encoder is absolute or relative does affect whether an encoder needs to be indexed when it powers up, but does not directly affect whether the clutches can be released without losing position or not.  I have no direct experience with high resolution encoders (my AP1600 does not have them).  It's my understanding, though, that the 10Micron mounts have the encoders mounted such that you can release the clutches, power the mount off, whatever, and the mount will maintain orientation.  It's also my understanding that the Astro-Physics encoders will retain orientation through power cycles, but not if you release the clutches.  If you release the clutches on an AP mount with encoders, you need to re-index them via a homing procedure.  If you do not release the clutches, though, they will never lose orientation because they are absolute.  The difference between these systems is where the encoders actually make their measurements (ie. before or after the clutches).  I would be happy to be corrected on this if I am wrong.

 

I don't have a list of mounts that will retain alignment with the clutches released, but I think that there are a handful of them that are not in the premium mount price range.  None of my current mounts will do that.  I did have a Celestron Ultima 2000 that could be moved manually without losing alignment.  I used to keep the clutches on that mount somewhat loose.  It would track and slew for goto, but I could just push it so that the clutches slipped if I wanted to, and it would result tracking and not be lost when I let go of it.  It was a pretty neat feature, but I've lived without it for a long time now.


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#11 jdupton

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Posted 19 June 2017 - 05:25 PM

Wade,

 

There are many uses of the term "encoders" and I think that there is some confusion in the thread.

 

Wade,

   That is an excellent summary you made above. I also see an abundance of confusion whenever the subject of encoders come up. As you clearly stated, there are differing aspects to encoders as used in telescope mounts. We have examples of relative vs absolute, high resolution vs low resolution, direct vs indirect, and physical vs virtual. (This last category is how I explain some differences seen in mounts.)
  
   I am far from an expert on this with limited experience on a limited number of mounts, so corrections are welcome if I have any of this summary wrong.
  
   As simple summary could be made lumping mount encoder types into four categories I will call A, B, C, and D:
  
A) Virtual Encoders
Mounts using virtual encoders are most often stepper motor driven. There is no actual encoder to be found in the drive train. Instead, the motor control board keeps count of steps (and micro-steps) of the motor as it drives the telescope. The motor drive electronics counts each discrete change it can make as an encoder "tick". Thus, a mount with a micro-stepped 200 step per revolution stepper motor with 64 micro-steps (discrete positions of a full step) can generate 200 x 64 = 12,800 ticks of its virtual encoder per motor revolution that is then reduced through a gear box and final worm / worm wheel to drive the telescope axis. The number of ticks of "resolution" of the virtual encoder is increased by the gear reduction through the gear-box and final worm. Total tick counts projected into the sky can exceed 2 million for sub arc-second resolution.

 

A mount with a virtual encoder loses its position in the sky if the mount is manually moved rather than slewed under control of the motor drive electronics. All information about the mount's pointing position is lost when it is powered down.

 

Examples of Virtual Encoder Mounts
Orion Atlas EQG / SkyWatcher NEQ6

Orion Sirius EQ-G / SkyWatcher HEQ5    (Added edit)
... Many others ...

 

B) Motor Position Encoders
Mounts using motor position encoders are most often associated with servo motor drive systems. In this case, a physical encoder is coupled (usually directly) to the motor shaft so that its movement can be directly detected. These encoders often have tick counts on the order of 200 to 800 ticks per revolution of the motor. The motor is coupled to the telescope drive axis through a reduction gear-box and final worm / worm wheel mechanism. Total tick counts projected into the sky can exceed 2 million for sub arc-second resolution.

 

A mount with a motor position encoder loses its position in the sky if the mount is manually moved rather than slewed under control of the motor drive electronics. All information about the mount's pointing position is lost when it is powered down.

 

Examples of Motor Encoder Mounts
Celestron CGEM / CGEM DX
... many others ...

 

C) Relative Axis Encoder
Mounts with relative axis encoders use an encoder directly attached to the axes of the telescope. These encoders report a number of ticks as the axis moves through 360 degrees of motion. Resolution is often in the range of 8,000 to 20,000+ ticks per revolution giving arc-minute resolution in the sky.

 

A mount with a relative axis encoder can maintain its position information of where it is pointed in the sky if the mount is manually moved rather than slewed under control of the motor drive electronics. The pointing accuracy after such a manual movement is generally less than the original accuracy of a slew since the encoder has lower resolution than the underlying motor movement encoder (virtual or motor position) information. All information about the mount's pointing position is lost when it is powered down.

 

Examples of Motor Encoder Relative Axis Encoder Mounts
Orion HDX110 EQG / SkyWatcher EQ8

Sky-Watcher AZ-EQ6 / Orion Atlas Pro AZ/EQ-G   (Added edit)

Sky-Watcher AZ-EQ5 / Orion Sirius Pro AZ/EQ-G    (Added edit)
... others ...

 

D) Absolute Axis Encoder
Mounts with absolute axis encoders use special encoders directly attached to the axes of the telescope. These encoders not only report count ticks as the axis moves, they also report where in the 360 degree position of a full revolution they are currently positioned at all times. Positional resolution can range from arc-minute to sub-arc-seconds in the sky.

 

A mount with an absolute axis encoder can maintain its position information of where it is pointed in the sky if the mount is manually moved rather than slewed under control of the motor drive electronics. There is no loss of pointing accuracy after such a manual movement. All information about the mount's pointing position is maintained when it is powered down. Upon powering up the mount it already knows where it is pointing (by reading the encoders) without having to align on a star. (Star alignment may still be useful to sync any time or observer location information with the encoder positional data.)

 

Examples of Motor Encoder Absolute Axis Encoder Mounts
10-Micron GM1000HPS, 10-Micron GM2000HPS, etc.
AstroPhysics 1100GTO-AE, 1100GTO-AEL, etc

Paramount ME II + On-Axis Encoders    (Added edit)

Paramount Taurus Model 400 OAE    (Added edit)
Paramount Taurus Model 500    (Added edit)

Paramount Taurus Model 600    (Added edit)

... others ...

 

 
John


Edited by jdupton, 19 June 2017 - 06:39 PM.

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#12 robininni

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Posted 19 June 2017 - 07:36 PM

Thank you all for the great, detailed responses.  How wonderfully explained!



#13 PirateMike

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Posted 20 June 2017 - 02:08 AM

The Orion AZ/EQ-G (and Skywatcher) has encoders. You can manually move the scope around and the mount will continue to know where it is. 


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#14 rmollise

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Posted 20 June 2017 - 04:50 PM

Any electronic push-to or go-to mount will have some type of encoders. Most modern mounts can be configured to include encoders. Most mounts that include encoders can be modified to a different encoder configuration.

 

The list of current production mounts without encoders is likely shorter than the list of those that include them.

 

I don't believe he's talking about the (integral) encoders on the motors. He's talking about external encoders that will let you move the mount by hand.

 

The EQ-8 and the two SynScan AZ-EQ mounts have them for sure. No doubt they are on some of the more expensive GEMs, too, but since I am not an expensive GEM kinda guy I couldn't tell you which. ;)


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#15 ABQJeff

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Posted 15 September 2020 - 09:38 PM

I know this is an old post, but the Orion Star Seeker IV mounts and Orion Atlas Pro AZ/EQ-G both can be moved manually without losing their position (so "relative encoders"?) so you can actively switch between goto and manual.


Edited by ABQJeff, 15 September 2020 - 09:39 PM.


#16 photoracer18

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Posted 16 September 2020 - 06:36 PM

I am looking for mounts (GEM) that allow you to unlock the clutches and move the mount and the mount not lose alignment.  I don't think that is super common, is it?  I know my Atlas mount won't do that.

That is what is known as relative encoders. My G11 Gemini 1 is setup that way with the factory encoders and the cable plugged into a special port on the Gemini 1 controller.



#17 SamTheMan

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Posted 10 January 2021 - 01:32 PM

I successfully installed encoders and the Lumicon Sky Vector I (old, I know) on my Meade 826 GEM.  I had this listed on CN.  maybe you saw it.

Any way, I'll be receiving my Cave Astrola GEM with 1 1/2" shafts soon and plan to add DSCs to it also.

Anyone have any spare parts that might help with the encoder installation?  I have encoders and cabling and the DSC.  I just needs, gears, cogs, belts...what ever hardware you might have that could be adapted to a 1 1/2 shaft mount.

Thx

Sam



#18 JethroXP

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Posted 18 March 2021 - 09:08 AM

Adding to the list for absolute encoders:

Sky-Watcher EQ8-Rh (23-bit)

Avalon M-Due (21-bit)



#19 MJB87

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Posted 18 March 2021 - 09:20 AM

 It's also my understanding that the Astro-Physics encoders will retain orientation through power cycles, but not if you release the clutches.  If you release the clutches on an AP mount with encoders, you need to re-index them via a homing procedure.  If you do not release the clutches, though, they will never lose orientation because they are absolute.  

The Mach2 comes with absolute encoders and will not lose its positional awareness if you release the clutches and move the mount around, at least on the Mach2.  The encodings are on the axis housing itself, not the motor or gears, so moving the mount does not affect the position of the encoders. Roland says there is a lot of misunderstanding about this. (I am one of those who has been confused.)

 

For the record, absolute encoders are an option on the A-P 1100 and A-P 1600 mounts and can be retrofitted to an existing mount. The absolute encoders are integrated (not an option) on the Mach2 and therefore not optional (though you can turn them off if for some reason you wanted to.)



#20 rgsalinger

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Posted 18 March 2021 - 10:14 AM

"A Renishaw incremental 11.8 million tick encoder is installed on the RA axis of the EQ8-Rh virtually eliminating Periodic Error" means that the encoders on these mounts like the ones on the iOptron mounts are not absolute encoders. Renishaw (from the website) appears to make both incremental (relative) and absolute encoders. 

 

Rgrds-Ross


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#21 JethroXP

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Posted 18 March 2021 - 12:06 PM

"A Renishaw incremental 11.8 million tick encoder is installed on the RA axis of the EQ8-Rh virtually eliminating Periodic Error" means that the encoders on these mounts like the ones on the iOptron mounts are not absolute encoders. Renishaw (from the website) appears to make both incremental (relative) and absolute encoders. 

 

Rgrds-Ross

Good catch!  I've seen a review of the EQ6-Rh and the encoders seem to provide a very significant advantage for tracking, even making guiding unnecessary.  What benefit would absolute encoders (such as in the Avalon M-Due) provide that relative encoders don't?

http://philhart.com/skywatcher-eq8-rh



#22 WadeH237

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Posted 18 March 2021 - 07:11 PM

What benefit would absolute encoders (such as in the Avalon M-Due) provide that relative encoders don't?

It's not strictly absolute vs. relative that makes the difference.

 

It just happens that Renishaw's best relative encoders are less precise than their best absolute encoders.  It's that precision that's the important part - and also what drives the high cost.  The relative encoders are also lots more susceptible to SDE (sub-divisional error; here is an article with a description), which has been an issue for some folks that have mounts with relative encoders.


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#23 JethroXP

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Posted 18 March 2021 - 07:59 PM

Ok, let me see if I understand this correctly:

 

Relative Encoder:  I wake up, take 100 steps, and can retrace those steps precisely.  When I fall asleep, or if it snows, I don't know where I am anymore.  I only know where I am relative to where I've been since I've been awake.  Or maybe I made a map before I went to sleep so I'll remember when I wake up.  But if I fall asleep in a moving car I'll wake up lost for sure.

 

Absolute Encoder:  Hand held GPS, I could be asleep in a moving car and when I wake up I still know exactly where I am.

 

And the resolution/precision is the space between those steps?  So Relative could be more precise than Absolute if I'm taking 12-inch steps, but the GPS is only accurate to within 1-meter?

 

The EQ8-Rh with it's 23-bit relative encoders has a precision of about 0.15 arcsecond, while the Avalon M-Due and it's 21-bit absolute encoders has a precision of about 0.62 arcseconds.  But the Avalon will always know where it is (in both axis') even if bumped or manually moved by loosening the clutch, while the EQ8-Rh would need to be re-aligned?


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#24 rockstarbill

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Posted 19 March 2021 - 03:13 AM

The EQ8Rh costs way too much to even consider it as an option. You get a single axis incremental encoder, along with some of the build problems folks have posted here and other places about. When you get into the $7-8k range you're really better off looking at 10um and Astro-Physics for a little more money.

Edited by rockstarbill, 19 March 2021 - 03:14 AM.


#25 rockstarbill

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Posted 19 March 2021 - 08:33 AM

No offense, but I had to chuckle at a guy with two Astro-Physics mounts claiming that an $8000 mount costs way too much to even consider as an option lol.gif I understand your point, that you believe the EQ8-Rh isn’t worth the money and that for the same or slightly more money a much better mount can be had, it was just the wording that made me giggle.


You should read all of what someone says before judging them.


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