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Equipment Discussions >> Mounts

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bigj
member


Reged: 05/07/13

Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: Calypte]
      #5891707 - 05/30/13 01:56 AM

can you post the native PE date and photos when you get your mount

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bigj
member


Reged: 05/07/13

Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: Calypte]
      #5891727 - 05/30/13 02:17 AM

Cannot wait to see the Native PE and 15 minute sup from such an expensive mount. God I hope you do not put a small APO on this beast

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bigj
member


Reged: 05/07/13

Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: Calypte]
      #5891787 - 05/30/13 04:14 AM

Cannot wait for the raw data on the PE and photos

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frolinmod
Carpal Tunnel


Reged: 08/06/10

Loc: Southern California
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: wolfman_4_ever]
      #5892463 - 05/30/13 01:39 PM

Which mount did you decide to purchase?

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wolfman_4_ever
Pooh-Bah


Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: bigj]
      #5908570 - 06/07/13 07:00 PM

Quote:

can you post the native PE date and photos when you get your mount




Yes


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wolfman_4_ever
Pooh-Bah


Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: bigj]
      #5908572 - 06/07/13 07:01 PM

Quote:

God I hope you do not put a small APO on this beast




No..


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wolfman_4_ever
Pooh-Bah


Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: frolinmod]
      #5909156 - 06/08/13 03:00 AM

Quote:

Which mount did you decide to purchase?





AP1600 with encoders.


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dawziecat
Carpal Tunnel
*****

Reged: 10/20/10

Loc: Rural Nova Scotia
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: wolfman_4_ever]
      #5909357 - 06/08/13 08:38 AM

Quote:

AP1600 with encoders.





This post is NOT meant to be combative as when it comes to battle over the benefit to cost ratio for encoders, I am an unarmed man trying to find his way.

I have read the feature list for encoders. I have seen the A-P Sky and Tel NEAF 2013 video.

But I still don't see what these encoders offer as anything other than insanely little for their daunting cost. Most of what they address is handled by guiding.

Not having to home, reduced PE, reduced dec backlash. All very nice of course. But the cost is $7480 for the 1600.

I have to ask myself if this makes sense and I have worries about the longevity of these little slectronic gizmos too.

I am waiting for the AP1100. I don't plan on the encoder option. I am still unsure of what I will really be missing other than the above I mentioned.

I am assuming the 1100 will use the same encoders, at the same cost, as the 1600. So, they're a $7,480 "option" on an $8,800 mount.

So, Dave, what is it that made you decide to spring for the encoders?


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David PavlichAdministrator
Transmographied
*****

Reged: 05/18/05

Loc: Mandeville, LA USA
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: dawziecat]
      #5909444 - 06/08/13 09:49 AM

Quote:

Quote:

AP1600 with encoders.





This post is NOT meant to be combative as when it comes to battle over the benefit to cost ratio for encoders, I am an unarmed man trying to find his way.

I have read the feature list for encoders. I have seen the A-P Sky and Tel NEAF 2013 video.

But I still don't see what these encoders offer as anything other than insanely little for their daunting cost. Most of what they address is handled by guiding.

Not having to home, reduced PE, reduced dec backlash. All very nice of course. But the cost is $7480 for the 1600.

I have to ask myself if this makes sense and I have worries about the longevity of these little slectronic gizmos too.

I am waiting for the AP1100. I don't plan on the encoder option. I am still unsure of what I will really be missing other than the above I mentioned.

I am assuming the 1100 will use the same encoders, at the same cost, as the 1600. So, they're a $7,480 "option" on an $8,800 mount.

So, Dave, what is it that made you decide to spring for the encoders?




Read through this thread and you'll see why encoders are so much desired. 20 minutes unguided at a 2400mm focal length is pretty impressive. Is it worth $7400? If it's in the budget, then yes!

David


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Alph
Carpal Tunnel


Reged: 11/23/06

Loc: Melmac
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: David Pavlich]
      #5909680 - 06/08/13 12:36 PM

Quote:

Read through this thread and you'll see why encoders are so much desired. 20 minutes unguided at a 2400mm focal length is pretty impressive. Is it worth $7400? If it's in the budget, then yes!



If that's the goal then Telescope Drive Master will do for much less.


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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]
      #5909742 - 06/08/13 01:16 PM

Quote:

Quote:

Read through this thread and you'll see why encoders are so much desired. 20 minutes unguided at a 2400mm focal length is pretty impressive. Is it worth $7400? If it's in the budget, then yes!



If that's the goal then Telescope Drive Master will do for much less.




Maybe, but only in one axis.


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dawziecat
Carpal Tunnel
*****

Reged: 10/20/10

Loc: Rural Nova Scotia
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: EFT]
      #5909791 - 06/08/13 01:39 PM

Quote:

Maybe, but only in one axis.




I don't understand the function of an encoder on the dec axis at all for AP.
Forget whether it can or can not "eliminate" dec backlash. I gather that is a controversial claim.

The guider must still send corrections to the mount for errors in dec. What does the encoder do then? It must assume perfect alignment and no movement in dec at all, does it not? And the guider is trying to move the dec axis because alignment is never perfect? What happens? Who wins this tug of war, guider or encoder? The guider must, so why have the dec encoder at all? I am confused. I am also talking only about encoder use in AP. Not concerned with the mount never being "lost in space."

The unguided images taken by encoder-equipped mounts are pretty impressive though.

I am asking out of serious interest. If I were to be convinced these things really would make a huge difference, I just might (gulp!) reconsider buying my AP1100 with them.


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Mike7Mak
Pooh-Bah
*****

Reged: 12/07/11

Loc: New York
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: dawziecat]
      #5909976 - 06/08/13 03:43 PM

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.

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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: dawziecat]
      #5910040 - 06/08/13 04:21 PM

Quote:

Quote:

Maybe, but only in one axis.




I don't understand the function of an encoder on the dec axis at all for AP.
Forget whether it can or can not "eliminate" dec backlash. I gather that is a controversial claim.

The guider must still send corrections to the mount for errors in dec. What does the encoder do then? It must assume perfect alignment and no movement in dec at all, does it not? And the guider is trying to move the dec axis because alignment is never perfect? What happens? Who wins this tug of war, guider or encoder? The guider must, so why have the dec encoder at all? I am confused. I am also talking only about encoder use in AP. Not concerned with the mount never being "lost in space."

The unguided images taken by encoder-equipped mounts are pretty impressive though.

I am asking out of serious interest. If I were to be convinced these things really would make a huge difference, I just might (gulp!) reconsider buying my AP1100 with them.




First and foremost is the often sought goal of unguided imaging. Double absolute encoder systems allow for highly accurate tracking with less reliance on polar alignment. The availability of double absolute encoder systems is really in answer to the never ending goal of many astro imagers to achieve the unguided AP nirvana that so many seek.

In regards to guiding, the mounts can still be guided when the target so requires it, but guiding adjustments can be taken to their absolute minimum and are made in both axes. The encoders resolve the vast majority of the mechanical errors of the mount (which all mounts have) leaving the guiding to deal mostly with any flexure and refraction issues that remain with the imaging system and the sky.

Dual absolute encoder systems also allow for building of highly accurate and stable pointing models. Such models are of particular interest those people conducting imaging (especially remote imaging) of multiple targets or fast survey work like supernova searches.

Finally, dual absolute encoder systems can be run at much higher speeds than autoguided systems making them suitable for observation and imaging of fast moving objects like asteroids and satellites.

While similar performance can be obtained through the use of a direct drive mount, those mounts remain extremely expensive and uncommon at this point and have a tendency to be either very large or small and less robust than some of these higher-end worm drive systems.

Does everyone need such as system? No. A lot can be done with very well guided mounts that do not have absolute encoders. But dual absolute encoder systems remove the mount from the guiding challenge almost completely as is the goal of direct drive mounts. For those and need it and can afford it, it's the way to go.


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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: Mike7Mak]
      #5910046 - 06/08/13 04:25 PM

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.


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dawziecat
Carpal Tunnel
*****

Reged: 10/20/10

Loc: Rural Nova Scotia
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: EFT]
      #5910181 - 06/08/13 06:01 PM

I still don't see it. Help me please.
The encoders do not "see" the star the way a guider does. In fact they will happily track all night under thick cloud . . . or during day, pointed at a clear blue sky, for that matter. They "track" only the angular rotation of the axis.
When imaging, the dec axis is not supposed to have any angular rotation at all!
So, when imaging, what is the function of the encoder on the dec axis? The dec axis is not supposed to move at all, assuming perfect alignment. Yet, when connected to an autoguider, the guider will certainly send orders to move the dec axis.
How does the dec encoder respond to that?

Unguided images are not an especial goal of mine, and not at an extremely high cost. Perfectly tracked images are my goal. I expect I will have to OAG to get that, encoder equipped or not.

There is an example alluded to in the thread of a 20 minute unguided sub at 2400mm IIRC. Impressive for sure. But surely an extremely accurate polar alignment is essential to achieve that . . . far more accurate than I ever see myself having in my mobile rig.

Edited by dawziecat (06/08/13 06:01 PM)


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Mike7Mak
Pooh-Bah
*****

Reged: 12/07/11

Loc: New York
Re: Mount Upgrade Time! AP, SB, 10Micron, etc new [Re: EFT]
      #5910195 - 06/08/13 06:10 PM

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.


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Mount Upgrade Time! AP, SB, 10Micron, etc [Re: dawziecat]
      #5910305 - 06/08/13 08:02 PM

Quote:

I still don't see it. Help me please.
The encoders do not "see" the star the way a guider does. In fact they will happily track all night under thick cloud . . . or during day, pointed at a clear blue sky, for that matter. They "track" only the angular rotation of the axis.
When imaging, the dec axis is not supposed to have any angular rotation at all!
So, when imaging, what is the function of the encoder on the dec axis? The dec axis is not supposed to move at all, assuming perfect alignment. Yet, when connected to an autoguider, the guider will certainly send orders to move the dec axis.
How does the dec encoder respond to that?

Unguided images are not an especial goal of mine, and not at an extremely high cost. Perfectly tracked images are my goal. I expect I will have to OAG to get that, encoder equipped or not.

There is an example alluded to in the thread of a 20 minute unguided sub at 2400mm IIRC. Impressive for sure. But surely an extremely accurate polar alignment is essential to achieve that . . . far more accurate than I ever see myself having in my mobile rig.




"Assuming perfect [polar] alignment." That is part of it right there. What this type of system relies on is a very accurate model over a very accurate polar alignment. In essence, the mount can be set up, a roughly polar aligned and a group of modeling stars quickly centered and off you go. Polar alignment does not have to be perfect, nor is it necessary to rely completely on a guider to tell the DEC axis to move one way or another, which it may or may not do depending on stiction, backlash, etc.

You can find many mounts where it is obvious that the DEC axis is considered unimportant and is less well built than the RA axis as a result. In a perfect world with perfect polar alignment, that would be fine, but this is not a perfect world. With careful drift alignment you can certainly get close, but never perfect (someone who deals with large professional observatories would have to tell you how procession is ultimately dealt with in those systems).

I don't write the software that these systems use so I can't tell you how they prioritize movement between the encoders and a guider.

Whether or not you want or need unguided imaging or even imaging up to these standards is entirely up to you (and your pocketbook). A lot can be done with less certainly. Does everyone need to go out and spend this kind of money on a mount just to do any level of AP? No. But all you have to do is look around on the forums to see how many people struggle to do unguided AP on mounts that are simply incapable of it. For those that really want to do that, double absolute encoder systems are a way it may be accomplished, but it simply can't be done cheaply.

Should you spend as much to add on encoders as you spend on the mount? Again, that's up to you. The difference isn't that much in some systems while it may be in other systems. Should you spend as much or more on an encoder system as you spend on your mount to try to improve a lesser quality mount? There are arguments both ways on that as well.

Besides the ability of these systems to track non-sidereal objects and be up and running quickly at mobile sites, something else they excel at is remote imaging. Power loss is not a problem because as long as the mount knows the date time and location, it knows exactly where it is pointing, period. Wind gusts (or even bumping into the OTA) don't matter because the mounts can almost instantaneously correct for such movements.

When it comes down to it, the relatively recent rise of these double absolute encoder systems is a purely market driven phenomenon. It would be great if it were cheaper and we would all have them in that case. But at this point there is no way to do this on the cheap so you have to decide whether it is worth it to you or not. If not, I wouldn't agonize over it.


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Mount Upgrade Time! AP, SB, 10Micron, etc [Re: Mike7Mak]
      #5910311 - 06/08/13 08:08 PM

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.


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Mike7Mak
Pooh-Bah
*****

Reged: 12/07/11

Loc: New York
Re: Mount Upgrade Time! AP, SB, 10Micron, etc [Re: EFT]
      #5910332 - 06/08/13 08:22 PM

No problem Ed, I was just observing that the tech to read data off a circular disc exists in dirt cheap consumer disc players. Seems like it could be applied to some sort of basic drive rate control system.

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