New Addition to the family


dvjbaja
 

Just added to the collection. 

Could be argued, the finest grab and go system known to humankind. 

-j


Eric Weiner
 

Which version did you buy, the 135 or 300? Did you get it new? I’d be curious to hear your thoughts in much greater detail on that mount. They are quite pricey for the claimed tracking accuracy imho, and I have only seen them claim a specific number for the 135E (+\- 2.5arcsec PE). If you’re willing, please submit some PHD tracking logs. I would really like to own something as portable as one of those, but for $6-8k I would personally need better than 2.5arcsec PE. Cough cough AP.... 


Jerome Allison
 

How do you like the T-Pod tripod?  I've been interested in the 110 model, but still on the fence.


Roland Christen
 

Strain wave gears are very light weight for their payload ability, that's why they are used in robots. They have inherent periodic error which is in the neighborhood of 90 arc seconds P-P with a triangular shape that produces a tracking change of approximately 0.5 arc seconds per second as each of the teeth engage and disengage. One can add an encoder ring on the output rotating portion of the gear, however there is a limitation. The output "shaft" oscillates back and forth slightly as it turns. The encoder ring follows that motion and the resultant runout produces an error in the encoder reading which limits the accuracy to around 5 arc seconds.

My own thoughts about a small mount is that we can build a worm wheel drive that doesn't weigh much more than the strain wave gear, but it needs a balanced load to be efficient (thus counterweights). Adding a similar encoder would result in sub-arc sec accuracy in tracking. Since Dec doesn't need to track, it could be made from a strain wave gear, and the result would be a hybrid. Having a worm drive in RA would eliminate the back drive issue.

Then the question becomes, does the market want a basic clutchless mount that always needs to be powered to move around the sky, or would a clutched mount be a more desirable item. A clutched mount can be moved around manually and then locked down for Go-To and imaging applications. It would be a more universal mount. In fact it can have dual absolute encoders so that it becomes pretty much transparent to even a beginner (like the Mach2).

Rolando



-----Original Message-----
From: Eric Weiner <weinere@...>
To: main@ap-ug.groups.io
Sent: Sat, Apr 24, 2021 2:51 am
Subject: Re: [ap-ug] New Addition to the family

Which version did you buy, the 135 or 300? Did you get it new? I’d be curious to hear your thoughts in much greater detail on that mount. They are quite pricey for the claimed tracking accuracy imho, and I have only seen them claim a specific number for the 135E (+\- 2.5arcsec PE). If you’re willing, please submit some PHD tracking logs. I would really like to own something as portable as one of those, but for $6-8k I would personally need better than 2.5arcsec PE. Cough cough AP.... 


James Stone
 

My own opinion, for what it may be worth, is that there is a market for these small mounts, despite their limitations. Though I have an AP1200 and 1100 hopefully arriving soon, I personally just acquired one of these strain wave gear mounts (RST-135) even given its limitations for the “grab and go” convenience of it. I would far prefer an ultralight AP “grab and go” if that were an option.

 

 

From: <main@ap-ug.groups.io> on behalf of "Roland Christen via groups.io" <chris1011@...>
Reply-To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Date: Saturday, April 24, 2021 at 12:42 PM
To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Subject: Re: [ap-ug] New Addition to the family

 

Strain wave gears are very light weight for their payload ability, that's why they are used in robots. They have inherent periodic error which is in the neighborhood of 90 arc seconds P-P with a triangular shape that produces a tracking change of approximately 0.5 arc seconds per second as each of the teeth engage and disengage. One can add an encoder ring on the output rotating portion of the gear, however there is a limitation. The output "shaft" oscillates back and forth slightly as it turns. The encoder ring follows that motion and the resultant runout produces an error in the encoder reading which limits the accuracy to around 5 arc seconds.

 

My own thoughts about a small mount is that we can build a worm wheel drive that doesn't weigh much more than the strain wave gear, but it needs a balanced load to be efficient (thus counterweights). Adding a similar encoder would result in sub-arc sec accuracy in tracking. Since Dec doesn't need to track, it could be made from a strain wave gear, and the result would be a hybrid. Having a worm drive in RA would eliminate the back drive issue.

 

Then the question becomes, does the market want a basic clutchless mount that always needs to be powered to move around the sky, or would a clutched mount be a more desirable item. A clutched mount can be moved around manually and then locked down for Go-To and imaging applications. It would be a more universal mount. In fact it can have dual absolute encoders so that it becomes pretty much transparent to even a beginner (like the Mach2).

 

Rolando

 

 

 

-----Original Message-----
From: Eric Weiner <weinere@...>
To: main@ap-ug.groups.io
Sent: Sat, Apr 24, 2021 2:51 am
Subject: Re: [ap-ug] New Addition to the family

Which version did you buy, the 135 or 300? Did you get it new? I’d be curious to hear your thoughts in much greater detail on that mount. They are quite pricey for the claimed tracking accuracy imho, and I have only seen them claim a specific number for the 135E (+\- 2.5arcsec PE). If you’re willing, please submit some PHD tracking logs. I would really like to own something as portable as one of those, but for $6-8k I would personally need better than 2.5arcsec PE. Cough cough AP.... 


Eric Weiner
 

Thanks for that info Rolando. Much appreciated. That explains the 5” pp for the 135E. 

 Then the question becomes, does the market want a basic clutchless mount that always needs to be powered to move around the sky, or would a clutched mount be a more desirable item.”

My vote would be for a clutched mount with encoders Rolando. I’m fairly certain you’d get enough early orders to make it a very profitable venture. I would be one, of many, willing to place that order the day AP announces it. 

Regards,
Eric 


dvjbaja
 

Ans: RST-135, new. Stowaway, new.  Mount cost not $6K-$8K.  It has the flexibility for alt-az and EQ operation and weighs nothing.  These models work great with multi-star PHD2 tracking set up.  I am only using this mount in alt-az for visual with the Stowaway 92 and a host of other small refractors including an FSQ EDX 4.  In alt-az,  3 star alignment is all you need and in 5 minutes you are off and running with great pointing accuracy.  So far, I have been very impressed.  Dampening time is nil. Slewing is fast and accurate.  Don't underestimate the joy of observing in alt-az. Great eyepiece position. No counterweight.  

Sold my 600 goto and beautiful Mach 1 a few years back. Wanted something small and premium for my lightsippers.  The RST-135 fit the requirements as my 1100 supports the big imaging gear. 

The Avalon 110 tripod is rock solid, but I wish it had fine leveling adjustment on the feet.  Still, very lightweight. And for travel, the RST goes on any camera tripod.  

Happy to read that AP may be considering a small, travel mount. It's a gap in their roadmap.  

BTW, that Stowaway?  Amazing optical and mechanical build quality. Well done. 

- jg


Eric Weiner
 

Congrats on the Stowaway. I apparently got back into this hobby much too late to have my name placed on any AP scope list. Green with envy when I read about folks getting their new 130s and 92s.


ROBERT WYNNE
 

I've wondered about the application of stepper motors and encoders as applied in CAT scanners. As I recall the worm drives were coupled to a "0" anti backlash screw head. The shaft fabricated with a quadruple helical thread ground on hardened 440 SS. This was years ago but the assembly did provide a stable set up for at least 3 years and then the bearing started to show wear. I recall having to reload all the ball bearings when accidently removing the shaft from the anti backlash screw head. Plus the entire set up was continually monitored by encoders to ensure precise slices. -Best, Robert

On 04/24/2021 9:42 AM Roland Christen via groups.io <chris1011@...> wrote:
 
 
St rain wave gears are very light weight for their payload ability, that's why they are used in robots. They have inherent periodic error which is in the neighborhood of 90 arc seconds P-P with a triangular shape that produces a tracking change of approximately 0.5 arc seconds per second as each of the teeth engage and disengage. One can add an encoder ring on the output rotating portion of the gear, however there is a limitation. The output "shaft" oscillates back and forth slightly as it turns. The encoder ring follows that motion and the resultant runout produces an error in the encoder reading which limits the accuracy to around 5 arc seconds.
 
My own thoughts about a small mount is that we can build a worm wheel drive that doesn't weigh much more than the strain wave gear, but it needs a balanced load to be efficient (thus counterweights). Adding a similar encoder would result in sub-arc sec accuracy in tracking. Since Dec doesn't need to track, it could be made from a strain wave gear, and the result would be a hybrid. Having a worm drive in RA would eliminate the back drive issue.
 
Then the question becomes, does the market want a basic clutchless mount that always needs to be powered to move around the sky, or would a clutched mount be a more desirable item. A clutched mount can be moved around manually and then locked down for Go-To and imaging applications. It would be a more universal mount. In fact it can have dual absolute encoders so that it becomes pretty much transparent to even a beginner (like the Mach2).
 
Rolando
 
 
 
-----Original Message-----
From: Eric Weiner <weinere@...>
To: main@ap-ug.groups.io
Sent: Sat, Apr 24, 2021 2:51 am
Subject: Re: [ap-ug] New Addition to the family

Which version did you buy, the 135 or 300? Did you get it new? I’d be curious to hear your thoughts in much greater detail on that mount. They are quite pricey for the claimed tracking accuracy imho, and I have only seen them claim a specific number for the 135E (+\- 2.5arcsec PE). If you’re willing, please submit some PHD tracking logs. I would really like to own something as portable as one of those, but for $6-8k I would personally need better than 2.5arcsec PE. Cough cough AP.... 


Roland Christen
 

There's a market for just about anything you can think up. However, there is also a limitation to what we can build. I also am hesitant to offer something that already exists and would rather produce a more accurate item, and something more universal.

Rolando



-----Original Message-----
From: James Stone <jrs7r@...>
To: main@ap-ug.groups.io <main@ap-ug.groups.io>
Sent: Sat, Apr 24, 2021 11:47 am
Subject: Re: [ap-ug] New Addition to the family

My own opinion, for what it may be worth, is that there is a market for these small mounts, despite their limitations. Though I have an AP1200 and 1100 hopefully arriving soon, I personally just acquired one of these strain wave gear mounts (RST-135) even given its limitations for the “grab and go” convenience of it. I would far prefer an ultralight AP “grab and go” if that were an option.
 
 
From: <main@ap-ug.groups.io> on behalf of "Roland Christen via groups.io" <chris1011@...>
Reply-To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Date: Saturday, April 24, 2021 at 12:42 PM
To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Subject: Re: [ap-ug] New Addition to the family
 
Strain wave gears are very light weight for their payload ability, that's why they are used in robots. They have inherent periodic error which is in the neighborhood of 90 arc seconds P-P with a triangular shape that produces a tracking change of approximately 0.5 arc seconds per second as each of the teeth engage and disengage. One can add an encoder ring on the output rotating portion of the gear, however there is a limitation. The output "shaft" oscillates back and forth slightly as it turns. The encoder ring follows that motion and the resultant runout produces an error in the encoder reading which limits the accuracy to around 5 arc seconds.
 
My own thoughts about a small mount is that we can build a worm wheel drive that doesn't weigh much more than the strain wave gear, but it needs a balanced load to be efficient (thus counterweights). Adding a similar encoder would result in sub-arc sec accuracy in tracking. Since Dec doesn't need to track, it could be made from a strain wave gear, and the result would be a hybrid. Having a worm drive in RA would eliminate the back drive issue.
 
Then the question becomes, does the market want a basic clutchless mount that always needs to be powered to move around the sky, or would a clutched mount be a more desirable item. A clutched mount can be moved around manually and then locked down for Go-To and imaging applications. It would be a more universal mount. In fact it can have dual absolute encoders so that it becomes pretty much transparent to even a beginner (like the Mach2).
 
Rolando
 
 
 
-----Original Message-----
From: Eric Weiner <weinere@...>
To: main@ap-ug.groups.io
Sent: Sat, Apr 24, 2021 2:51 am
Subject: Re: [ap-ug] New Addition to the family
Which version did you buy, the 135 or 300? Did you get it new? I’d be curious to hear your thoughts in much greater detail on that mount. They are quite pricey for the claimed tracking accuracy imho, and I have only seen them claim a specific number for the 135E (+\- 2.5arcsec PE). If you’re willing, please submit some PHD tracking logs. I would really like to own something as portable as one of those, but for $6-8k I would personally need better than 2.5arcsec PE. Cough cough AP.... 


James Stone
 

I guess a primary consideration is whether it is possible to embed the AP DNA in a very precise mount with a small, lightweight form factor that would approximate something like the footprint of the RST-135. If so, it seems like that could be a real differentiator from what currently exists. That said, I don’t know the first thing about what it takes to build a mount, much less operationalize an assembly for a run of mounts, and imagine this isn’t the first time this topic has been discussed both publicly and at AP. So I suspect there are probably some good reasons why this type of mount hasn’t made it into the AP product line.

 

 

From: <main@ap-ug.groups.io> on behalf of "Roland Christen via groups.io" <chris1011@...>
Reply-To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Date: Saturday, April 24, 2021 at 2:25 PM
To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Subject: Re: [ap-ug] New Addition to the family

 

There's a market for just about anything you can think up. However, there is also a limitation to what we can build. I also am hesitant to offer something that already exists and would rather produce a more accurate item, and something more universal.

 

Rolando

 

 

 

-----Original Message-----
From: James Stone <jrs7r@...>
To: main@ap-ug.groups.io <main@ap-ug.groups.io>
Sent: Sat, Apr 24, 2021 11:47 am
Subject: Re: [ap-ug] New Addition to the family

My own opinion, for what it may be worth, is that there is a market for these small mounts, despite their limitations. Though I have an AP1200 and 1100 hopefully arriving soon, I personally just acquired one of these strain wave gear mounts (RST-135) even given its limitations for the “grab and go” convenience of it. I would far prefer an ultralight AP “grab and go” if that were an option.

 

 

From: <main@ap-ug.groups.io> on behalf of "Roland Christen via groups.io" <chris1011@...>
Reply-To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Date: Saturday, April 24, 2021 at 12:42 PM
To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Subject: Re: [ap-ug] New Addition to the family

 

Strain wave gears are very light weight for their payload ability, that's why they are used in robots. They have inherent periodic error which is in the neighborhood of 90 arc seconds P-P with a triangular shape that produces a tracking change of approximately 0.5 arc seconds per second as each of the teeth engage and disengage. One can add an encoder ring on the output rotating portion of the gear, however there is a limitation. The output "shaft" oscillates back and forth slightly as it turns. The encoder ring follows that motion and the resultant runout produces an error in the encoder reading which limits the accuracy to around 5 arc seconds.

 

My own thoughts about a small mount is that we can build a worm wheel drive that doesn't weigh much more than the strain wave gear, but it needs a balanced load to be efficient (thus counterweights). Adding a similar encoder would result in sub-arc sec accuracy in tracking. Since Dec doesn't need to track, it could be made from a strain wave gear, and the result would be a hybrid. Having a worm drive in RA would eliminate the back drive issue.

 

Then the question becomes, does the market want a basic clutchless mount that always needs to be powered to move around the sky, or would a clutched mount be a more desirable item. A clutched mount can be moved around manually and then locked down for Go-To and imaging applications. It would be a more universal mount. In fact it can have dual absolute encoders so that it becomes pretty much transparent to even a beginner (like the Mach2).

 

Rolando

 

 

 

-----Original Message-----
From: Eric Weiner <weinere@...>
To: main@ap-ug.groups.io
Sent: Sat, Apr 24, 2021 2:51 am
Subject: Re: [ap-ug] New Addition to the family

Which version did you buy, the 135 or 300? Did you get it new? I’d be curious to hear your thoughts in much greater detail on that mount. They are quite pricey for the claimed tracking accuracy imho, and I have only seen them claim a specific number for the 135E (+\- 2.5arcsec PE). If you’re willing, please submit some PHD tracking logs. I would really like to own something as portable as one of those, but for $6-8k I would personally need better than 2.5arcsec PE. Cough cough AP.... 


ROBERT WYNNE
 

Here Here and hopefully more robust- Best, Robert

On 04/24/2021 11:25 AM Roland Christen via groups.io <chris1011@...> wrote:
 
 
There' s a market for just about anything you can think up. However, there is also a limitation to what we can build. I also am hesitant to offer something that already exists and would rather produce a more accurate item, and something more universal.
 
Rolando
 
 
 
-----Original Message-----
From: James Stone <jrs7r@...>
To: main@ap-ug.groups.io <main@ap-ug.groups.io>
Sent: Sat, Apr 24, 2021 11:47 am
Subject: Re: [ap-ug] New Addition to the family

My own opinion, for what it may be worth, is that there is a market for these small mounts, despite their limitations. Though I have an AP1200 and 1100 hopefully arriving soon, I personally just acquired one of these strain wave gear mounts (RST-135) even given its limitations for the “grab and go” convenience of it. I would far prefer an ultralight AP “grab and go” if that were an option.
 
 
From: <main@ap-ug.groups.io> on behalf of "Roland Christen via groups.io" <chris1011@...>
Reply-To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Date: Saturday, April 24, 2021 at 12:42 PM
To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Subject: Re: [ap-ug] New Addition to the family
 
Strain wave gears are very light weight for their payload ability, that's why they are used in robots. They have inherent periodic error which is in the neighborhood of 90 arc seconds P-P with a triangular shape that produces a tracking change of approximately 0.5 arc seconds per second as each of the teeth engage and disengage. One can add an encoder ring on the output rotating portion of the gear, however there is a limitation. The output "shaft" oscillates back and forth slightly as it turns. The encoder ring follows that motion and the resultant runout produces an error in the encoder reading which limits the accuracy to around 5 arc seconds.
 
My own thoughts about a small mount is that we can build a worm wheel drive that doesn't weigh much more than the strain wave gear, but it needs a balanced load to be efficient (thus counterweights). Adding a similar encoder would result in sub-arc sec accuracy in tracking. Since Dec doesn't need to track, it could be made from a strain wave gear, and the result would be a hybrid. Having a worm drive in RA would eliminate the back drive issue.
 
Then the question becomes, does the market want a basic clutchless mount that always needs to be powered to move around the sky, or would a clutched mount be a more desirable item. A clutched mount can be moved around manually and then locked down for Go-To and imaging applications. It would be a more universal mount. In fact it can have dual absolute encoders so that it becomes pretty much transparent to even a beginner (like the Mach2).
 
Rolando
 
 
 
-----Original Message-----
From: Eric Weiner <weinere@...>
To: main@ap-ug.groups.io
Sent: Sat, Apr 24, 2021 2:51 am
Subject: Re: [ap-ug] New Addition to the family
Which version did you buy, the 135 or 300? Did you get it new? I’d be curious to hear your thoughts in much greater detail on that mount. They are quite pricey for the claimed tracking accuracy imho, and I have only seen them claim a specific number for the 135E (+\- 2.5arcsec PE). If you’re willing, please submit some PHD tracking logs. I would really like to own something as portable as one of those, but for $6-8k I would personally need better than 2.5arcsec PE. Cough cough AP.... 
 
 


dvjbaja
 

In the meantime, I'm enjoying many blissful nights with the system shown.   The Stowaway is quite lovely and I am observing more than ever.  

 Cheers. 



Sent via the Samsung Galaxy Note9, an AT&T 5G Evolution capable smartphone


Bill Long
 

Still hoping for that 400AE. 👍


From: main@ap-ug.groups.io <main@ap-ug.groups.io> on behalf of Roland Christen via groups.io <chris1011@...>
Sent: Saturday, April 24, 2021 11:25 AM
To: main@ap-ug.groups.io <main@ap-ug.groups.io>
Subject: Re: [ap-ug] New Addition to the family
 
There's a market for just about anything you can think up. However, there is also a limitation to what we can build. I also am hesitant to offer something that already exists and would rather produce a more accurate item, and something more universal.

Rolando



-----Original Message-----
From: James Stone <jrs7r@...>
To: main@ap-ug.groups.io <main@ap-ug.groups.io>
Sent: Sat, Apr 24, 2021 11:47 am
Subject: Re: [ap-ug] New Addition to the family

My own opinion, for what it may be worth, is that there is a market for these small mounts, despite their limitations. Though I have an AP1200 and 1100 hopefully arriving soon, I personally just acquired one of these strain wave gear mounts (RST-135) even given its limitations for the “grab and go” convenience of it. I would far prefer an ultralight AP “grab and go” if that were an option.
 
 
From: <main@ap-ug.groups.io> on behalf of "Roland Christen via groups.io" <chris1011@...>
Reply-To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Date: Saturday, April 24, 2021 at 12:42 PM
To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Subject: Re: [ap-ug] New Addition to the family
 
Strain wave gears are very light weight for their payload ability, that's why they are used in robots. They have inherent periodic error which is in the neighborhood of 90 arc seconds P-P with a triangular shape that produces a tracking change of approximately 0.5 arc seconds per second as each of the teeth engage and disengage. One can add an encoder ring on the output rotating portion of the gear, however there is a limitation. The output "shaft" oscillates back and forth slightly as it turns. The encoder ring follows that motion and the resultant runout produces an error in the encoder reading which limits the accuracy to around 5 arc seconds.
 
My own thoughts about a small mount is that we can build a worm wheel drive that doesn't weigh much more than the strain wave gear, but it needs a balanced load to be efficient (thus counterweights). Adding a similar encoder would result in sub-arc sec accuracy in tracking. Since Dec doesn't need to track, it could be made from a strain wave gear, and the result would be a hybrid. Having a worm drive in RA would eliminate the back drive issue.
 
Then the question becomes, does the market want a basic clutchless mount that always needs to be powered to move around the sky, or would a clutched mount be a more desirable item. A clutched mount can be moved around manually and then locked down for Go-To and imaging applications. It would be a more universal mount. In fact it can have dual absolute encoders so that it becomes pretty much transparent to even a beginner (like the Mach2).
 
Rolando
 
 
 
-----Original Message-----
From: Eric Weiner <weinere@...>
To: main@ap-ug.groups.io
Sent: Sat, Apr 24, 2021 2:51 am
Subject: Re: [ap-ug] New Addition to the family
Which version did you buy, the 135 or 300? Did you get it new? I’d be curious to hear your thoughts in much greater detail on that mount. They are quite pricey for the claimed tracking accuracy imho, and I have only seen them claim a specific number for the 135E (+\- 2.5arcsec PE). If you’re willing, please submit some PHD tracking logs. I would really like to own something as portable as one of those, but for $6-8k I would personally need better than 2.5arcsec PE. Cough cough AP.... 


thefamily90 Phillips
 

An Alt/az mount that can track?



From: main@ap-ug.groups.io <main@ap-ug.groups.io> on behalf of Bill Long <bill@...>
Sent: Saturday, April 24, 2021 10:26:47 PM
To: main@ap-ug.groups.io <main@ap-ug.groups.io>
Subject: Re: [ap-ug] New Addition to the family
 
Still hoping for that 400AE. 👍


From: main@ap-ug.groups.io <main@ap-ug.groups.io> on behalf of Roland Christen via groups.io <chris1011@...>
Sent: Saturday, April 24, 2021 11:25 AM
To: main@ap-ug.groups.io <main@ap-ug.groups.io>
Subject: Re: [ap-ug] New Addition to the family
 
There's a market for just about anything you can think up. However, there is also a limitation to what we can build. I also am hesitant to offer something that already exists and would rather produce a more accurate item, and something more universal.

Rolando



-----Original Message-----
From: James Stone <jrs7r@...>
To: main@ap-ug.groups.io <main@ap-ug.groups.io>
Sent: Sat, Apr 24, 2021 11:47 am
Subject: Re: [ap-ug] New Addition to the family

My own opinion, for what it may be worth, is that there is a market for these small mounts, despite their limitations. Though I have an AP1200 and 1100 hopefully arriving soon, I personally just acquired one of these strain wave gear mounts (RST-135) even given its limitations for the “grab and go” convenience of it. I would far prefer an ultralight AP “grab and go” if that were an option.
 
 
From: <main@ap-ug.groups.io> on behalf of "Roland Christen via groups.io" <chris1011@...>
Reply-To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Date: Saturday, April 24, 2021 at 12:42 PM
To: "main@ap-ug.groups.io" <main@ap-ug.groups.io>
Subject: Re: [ap-ug] New Addition to the family
 
Strain wave gears are very light weight for their payload ability, that's why they are used in robots. They have inherent periodic error which is in the neighborhood of 90 arc seconds P-P with a triangular shape that produces a tracking change of approximately 0.5 arc seconds per second as each of the teeth engage and disengage. One can add an encoder ring on the output rotating portion of the gear, however there is a limitation. The output "shaft" oscillates back and forth slightly as it turns. The encoder ring follows that motion and the resultant runout produces an error in the encoder reading which limits the accuracy to around 5 arc seconds.
 
My own thoughts about a small mount is that we can build a worm wheel drive that doesn't weigh much more than the strain wave gear, but it needs a balanced load to be efficient (thus counterweights). Adding a similar encoder would result in sub-arc sec accuracy in tracking. Since Dec doesn't need to track, it could be made from a strain wave gear, and the result would be a hybrid. Having a worm drive in RA would eliminate the back drive issue.
 
Then the question becomes, does the market want a basic clutchless mount that always needs to be powered to move around the sky, or would a clutched mount be a more desirable item. A clutched mount can be moved around manually and then locked down for Go-To and imaging applications. It would be a more universal mount. In fact it can have dual absolute encoders so that it becomes pretty much transparent to even a beginner (like the Mach2).
 
Rolando
 
 
 
-----Original Message-----
From: Eric Weiner <weinere@...>
To: main@ap-ug.groups.io
Sent: Sat, Apr 24, 2021 2:51 am
Subject: Re: [ap-ug] New Addition to the family
Which version did you buy, the 135 or 300? Did you get it new? I’d be curious to hear your thoughts in much greater detail on that mount. They are quite pricey for the claimed tracking accuracy imho, and I have only seen them claim a specific number for the 135E (+\- 2.5arcsec PE). If you’re willing, please submit some PHD tracking logs. I would really like to own something as portable as one of those, but for $6-8k I would personally need better than 2.5arcsec PE. Cough cough AP.... 

--
Jim Phillips


albireo1313@...
 

Even a refresh of the AP400 would be awesome.