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Equipment Discussions >> Mounts

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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: famax]
      #5914584 - 06/11/13 07:08 AM

Per, is there any difference in alt/az knob system between GM2000HPS and GM1000HPS?
How does it work, any similarities with standard mounts like CGEM?


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Per Frejvall
sage


Reged: 09/28/12

Loc: Saltsjöbaden, Sweden
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: orion69]
      #5914612 - 06/11/13 07:58 AM

Knez,

Yes they differ but the firmware, even though it is the same in 1000, 2000 and 4000, naturally knows which mount it is handling and thus supplies the correct instructions.

I haven't seen a CGEM so I cannot comment on similarities... 10Micron uses fairly fine-threaded screws that push onto a metal block and I guess that is pretty standard practice. The altitude system is rack and pinion on the 1000 and push-screw on the 2000.

/per


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: Alph]
      #5914697 - 06/11/13 09:23 AM

Quote:

On the other hand, 10micron canít even make the user manual available for download. They have zero credibility.




Wrong as usual. The manuals are here:

GM1000HPS

GM2000HPS

GM4000HPS

Read away. Do you think I don't know what the US market wants?


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: famax]
      #5914745 - 06/11/13 10:02 AM

Quote:

A simple test on the 10Ķ gm1000 hps on this french website :
http://www.astrosurf.com/ubb/Forum2/HTML/038986.html




I love the Google translator that obviously turns what is "mount" in French to "horse" so that they are talking about hauling a horse around.


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R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: EFT]
      #5914763 - 06/11/13 10:15 AM

Thank you!!! At last some sense to this nonsense of no manual being available anywhere!

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psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: EFT]
      #5914767 - 06/11/13 10:21 AM

Per - thanks for the times. Just curious on how long it takes to set things up. Or, in my case, if I mess up, how long I have to do it over again.

Paul


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Alph
Carpal Tunnel


Reged: 11/23/06

Loc: Melmac
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: Per Frejvall]
      #5914798 - 06/11/13 10:40 AM

Quote:

T-point may model the sky perfectly (and I think it probably does) but it cannot read any positional feedback from the mount axis and thus can only apply corrections on a blind basis. 10Micron has the absolute encoders connected in the feedback control loop (along with the less accurate motor encoders) and produce a much tighter control pattern.



According to SB, the Paramount mounts can achieve all-sky pointing accuracy of 10 arc-seconds which is pretty close to your result of 6 arc-seconds that is not all-sky anyway. The Paramount ME II with hi-res on-axis encoders can achieve 5 arc-second all-sky pointing accuracy. The point being, the paramount mounts without hi-res encoders are very accurate yet they can't get PA under one arc-minute with a 15 point TPoint model.


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Per Frejvall
sage


Reged: 09/28/12

Loc: Saltsjöbaden, Sweden
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: Alph]
      #5914999 - 06/11/13 12:38 PM

I really suggest reading the document at http://10micron.de/informations/differences-between-mount-drives/?lang=en as it explains quite a bit about encoder technology.

As for the accuracy... If the scope is without irregular flexure and the pier or tripod steady, and I run a 100-star model, I can refine it down to 3" by loosing some of the worst points.

Now, the thing for me is not pointing accuracy at all, but rather tracking accuracy, and this is where 10Micron's products truly excel. We all plate solve anyway so pointing is not that key. With the encoders in the control loop all is well.

I think Bisque will have encoders ready late 2013 at the price of $3000 per axis. Luckily they state that the encoders will have to be installed at the factory, this in contrast to other mount manufacturers who state that they can be field installed. The latter I don't believe. Given the Bisque mounts excellent track record, I am sure that they will get this right. The mount is kind of exensive, though, at $16,500 (but with an impressive payload!).

I truly do not understand why hey can't get decent polar alignment though. Both my 10Micron mounts are easy to get sub-minute.

/p


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: Per Frejvall]
      #5915072 - 06/11/13 01:30 PM

Quote:

I really suggest reading the document at http://10micron.de/informations/differences-between-mount-drives/?lang=en as it explains quite a bit about encoder technology.

As for the accuracy... If the scope is without irregular flexure and the pier or tripod steady, and I run a 100-star model, I can refine it down to 3" by loosing some of the worst points.

Now, the thing for me is not pointing accuracy at all, but rather tracking accuracy, and this is where 10Micron's products truly excel. We all plate solve anyway so pointing is not that key. With the encoders in the control loop all is well.

I think Bisque will have encoders ready late 2013 at the price of $3000 per axis. Luckily they state that the encoders will have to be installed at the factory, this in contrast to other mount manufacturers who state that they can be field installed. The latter I don't believe. Given the Bisque mounts excellent track record, I am sure that they will get this right. The mount is kind of exensive, though, at $16,500 (but with an impressive payload!).

I truly do not understand why hey can't get decent polar alignment though. Both my 10Micron mounts are easy to get sub-minute.

/p




Installation at the factory is not at all surprising due to the precision requirements for these systems. I'm not sure what systems are field-installable other than the one add-on system out there and the adapters for that system are $400 which is not surprising considering the necessary level of precision. Increasing levels of precision is what you are paying for in all of these mounts, with and without absolute encoders. What is amazing is the professional level of precision that is now becoming available in amateur mounts now. Truly amazing.


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frolinmod
Carpal Tunnel


Reged: 08/06/10

Loc: Southern California
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: EFT]
      #5915268 - 06/11/13 03:26 PM

With Tpoint I always do a plate solved sync then at least 42 plate solved samples followed by a supermodel. I do not trust polar alignment reports done with fewer samples or without doing a supermodel.

It's certainly possible to get within one arc minute after the first adjustment (especially if you use CCD/video feedback while turning the altitude axis knob). But with only 15 samples it would be pure luck and more importantly perhaps not 100% accurate for lack of sufficient sampling.

Gather more samples well distributed over the sky and Tpoint will find all sorts of flexures and harmonic terms that cause it to produce a different polar alignment report. Perhaps one that shows that with these in mind that you're actually more than an arc minute off after all...


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coz
sage


Reged: 08/25/10

Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: frolinmod]
      #5915368 - 06/11/13 04:13 PM

AP says you can install yourself for the precision encoders.

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Alph
Carpal Tunnel


Reged: 11/23/06

Loc: Melmac
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: Per Frejvall]
      #5915419 - 06/11/13 04:48 PM

Quote:

As for the accuracy... If the scope is without irregular flexure and the pier or tripod steady, and I run a 100-star model, I can refine it down to 3" by loosing some of the worst points.



I think you are blindly trusting a tool that has no established record from a company that is afraid to publish the user manual.


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Per Frejvall
sage


Reged: 09/28/12

Loc: Saltsjöbaden, Sweden
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: coz]
      #5915435 - 06/11/13 04:56 PM

Coz,

Yes, AP was in my head when I wrote that but I didn't want to stir up any feelings

Absolute encoders need to be modeled themselves using even better and bigger encoders. At least that is what 10Micron, and I suspect Bisque, does. The encoder is put in place with rediculous precision and then the whole assembly is modeled with an even more rediculously accurate encoder thingy. The parameters for the encoder is then stored permanently in the mount. The results are staggering.

Frolinmod,

I am not familiar with the terms used by T-point, but I am certain that the mathematics are impeccable. As for number of samples needed for a reasonable polar alignment, I am not sure more is necessarily better.

If I run a 15 point and then adjust, clear the mount and run a 100 point model the result is always quite good with a low polar error. 10Micron uses complex model terms in their modeling algorithm and the more you get the better. A model usually results in 9 to 22 complex model terms and there is not a fixed correlation to the number of points. I visualize it as similar to a polynomial curve fitting, meaning the model won't actually hold corrections for different positions. Instead it holds the complex model terms that seamlessly warp the sky.

The 10Micron model computations yield polar error as well as orthogonal error and flexure. What it cannot do is model random flexure. It doesn't have to model harmonics as these eliminated already in the servo control loop. Given that, I guess the T-point algorithms are more advanced as they are used to correct harmonics as well.

Off to bed

/per


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: Alph]
      #5915453 - 06/11/13 05:06 PM

Quote:

I think you are blindly trusting a tool that has no established record from a company that is afraid to publish the user manual.




I guess I have to post this again for you. The manuals are here:

GM1000HPS

GM2000HPS

GM4000HPS

Sorry to burst your conspiracy bubble. No fear at all, it's just that some markets want different information than other markets. Seems to me that 10 years is at least a reasonable track record for a relatively new high-end mount company. You seem to be grasping at straws and name calling as usual.

If you have specific questions that don't involve company design secrets, then let's hear them so that they can be addressed. If you simply won't believe anything you read or are told, then please go design your own equipment and prove everyone wrong.

As for Per's software (which you seem to be alluding to), he will have to explain that, but other than not believing his results, you haven't presented anything to prove his software unsuitable or his methods wrong.


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Per Frejvall
sage


Reged: 09/28/12

Loc: Saltsjöbaden, Sweden
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: EFT]
      #5915466 - 06/11/13 05:12 PM

Quote:

Quote:

Quote:

Quote:

I don't get why encoder systems are so expensive. Seems to me you could whip one up with the guts of a dvd player. Once you've got the optical reader mechanics the rest is programming and control boards. I replaced a motor encoder on my LX200gps for less than 50 bucks IIRC.




Mike,

We're not talking about 4000 or even 10000 tic encoders with relative positioning here. We are talking about 10 million tic encoders with absolute positioning (i.e., they always know exactly where they are pointing in their rotation). These things are darned expensive. When you are looking for sub-arc.sec. tracking and pointing accuracy, 10000 tic encoders won't do the trick.



So you're saying you can't get 10 million optical ticks on the circumference of a dvd? What is the spacing of the 1s and 0s on a data disc? Maybe I'm just misunderstanding how data discs work.




I see what you are saying now, but I can't really answer that question since I don't make the things. Obviously, the large the encoder disk, the easier you can make more tics in it, so a lot of this has to do with miniaturization and accuracy along with the absolute position systems in the encoders which add another layer of complexity over the simple straight line tics that can be seen on the average 256 count optical encoder. Beyond that you would have to talk with someone who makes them, uses them in the equipment they manufacture or programs for them.




You cannot compare a CD player as it has the bits passing underneath it all the time but only gets the absolute position of the track very seldom. Besides, the absolute position comes serially which means it takes up a bunch of ticks in itself. Not doable.

A high resolution encoder needs to use some kind of pattern that increases the resolution. It also needs some mean of becoming absolute. A number of encoders are absolute only to a certain extent and rely on a small calibration at start up.

You can picture a hi res encoder as having a pattern with nine ticks per unit of distance on one "channel" and ten on another. When you interpolate the two you get a resolution that is higher than ten per unit. Exactly the same way callipers work actually.

Now transform the principle up to 12 million points to a revolution on a four inch wheel's circumference. Imagine the problem of making each interpolated tick absolute with its own value. You would probaly opt for a solution that has an absolute address available every 1000 interpolated steps or so and rely on the fact that you pass an address ever so often and then count your way from there. On startup the system would move the axis just a little bit back and forth in order to pick up the actual position on the "wheel", and then move back to where it was, now knowing exactly where it is. And it can go back to exactly where it was as it is recording what is happening with the ticks during the calibration.

Simple analogies but I believe they drive the point through. If you want to look at expensive and good encoders, then check out Renishaw.

Incidently, when I power either of my 10Micron mounts up it will do a very quick and hardly noticeable dance on each axis

/per


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: Per Frejvall]
      #5915491 - 06/11/13 05:22 PM

Quote:

Absolute encoders need to be modeled themselves using even better and bigger encoders. At least that is what 10Micron, and I suspect Bisque, does. The encoder is put in place with ridiculous precision and then the whole assembly is modeled with an even more ridiculously accurate encoder thingy. The parameters for the encoder is then stored permanently in the mount. The results are staggering.




This is my understanding of the process as well. Just look over at Orly's thread where he has been trying to make a homemade encoder system and the problems with machining and mounting accuracy become obvious. You can buy a high accuracy absolute encoder, but that doesn't mean you can slap it on something and make it work. Nothing is perfect so to increase the accuracy of a measuring system, the measuring system itself must be measured and adjusted for it's inherent inaccuracies. It all comes down to cost. The more accurate, the more expensive. When the cost comes down on one system, then a new even more accurate system arises and the cost cycle begins again.


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frolinmod
Carpal Tunnel


Reged: 08/06/10

Loc: Southern California
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: EFT]
      #5915526 - 06/11/13 05:37 PM

Quote:

It doesn't have to model harmonics as these eliminated already in the servo control loop.



Good point.


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psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: Per Frejvall]
      #5915535 - 06/11/13 05:40 PM

I don't know, after all the complicated gobbledegook (including the fact that Per's mount does some kind of dance, but not which dance - hopefully not Gangnam Style, or I'd have to pass on that mount), it really does turn out to be quite simple:

Guided or unguided - do you get nice small round stars? Any rotation? Trailing? Etc.? If you get great stars, then it works. The longer the subs, the better. If you don't get great stars, it doesn't work.

People can declaim "something is impossible because I say it's impossible," but if you throw up a pre-post picture and the stars look great, those people are just plain wrong. Seriously - if someone says they get 30 minute unguided and there's a picture with nice round tight stars doing that, and they never throw out subs...there is no debate.

So, really: do you get great stars? If you do, then it works, no matter what anyone who doesn't have the mount, never seen the mount says. If you don't, then the mount's not up to spec.

There, simple. Do you get great stars?

At least that's how I pick my mounts,

Paul


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Per Frejvall
sage


Reged: 09/28/12

Loc: Saltsjöbaden, Sweden
Re: Mount Upgrade Time! AP, SB, 10Micron, etc [Re: Alph]
      #5915550 - 06/11/13 05:50 PM

Quote:

Quote:

As for the accuracy... If the scope is without irregular flexure and the pier or tripod steady, and I run a 100-star model, I can refine it down to 3" by loosing some of the worst points.



I think you are blindly trusting a tool that has no established record from a company that is afraid to publish the user manual.




Oh, well... I guess 10Micron hasn't been peer-reviewed but which mount has?

The company has 35 years of precision mechanics experience of which 15 in the mounts division. The encoder design was developed in cooperation with Baader Planetarium, another company with an outstanding record.

Apparently the user manual is openly available.

Now, what was the point of your comment? I don't get it.


/per


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psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Mount Upgrade Time! AP, SB, 10Micron, etc [Re: Per Frejvall]
      #5915553 - 06/11/13 05:53 PM

Quote:

Now, what was the point of your comment? I don't get it.





I think it's Precision Mount Envy....


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