Date   

Re: Recent encoder discussion on CN

Roland Christen
 


So when I am moving the mount it will never be perfectly balanced.
No need to perfectly balance an 1100 mount.  5 lb out? Pfffft. 10 lb out, well that may require a bit of balancing.

Rolando


-----Original Message-----
From: Andrew Jones <andjones132@...>
To: main@ap-gto.groups.io
Sent: Fri, Feb 26, 2021 10:54 am
Subject: Re: [ap-gto] Recent encoder discussion on CN

On Fri, Feb 26, 2021 at 08:37 AM, Roland Christen wrote:
"Why would you ever release the lever to reposition the mount in the first place? Do you have a permanent setup such as a remote observatory system? In that case I cannot ever see why the mount would be moved manually. Do you have a temporary setup which you tear down after every session? In that case why would you care about knowing absolutely where the axes are pointed, since you will be starting off fresh anyway? Just loosen the clutches and place the mount in a known park position and start the session from there."
 
Rolando

Hi Roland.

Yes, my Mach1 is on a permanent pier in an Explora-Dome in my backyard. I have it setup so that I can image from the house and almost never have to go to the dome when imaging, However, I have a lot of other stuff one the mount like, focus controllers, dew heater controllers, USB hubs, etc. which I am always trying to refine the setup. When I am working on stuff during the day I will often reposition the scope so I can reach certain things easier. As you know with refractors, they will never be in balance unless they are in their imaging configuration with the focuser set to close to focus and the dew shield out. I don't put everything out in it's imaging configuration if I am just working on the mount or switching out other components. So when I am moving the mount it will never be perfectly balanced. I try to have a good hold on the OTA before I release the gearbox levers, but it can still move a bit. 
 

--
Roland Christen
Astro-Physics


Re: Small mount was Recent encoder discussion on CN

Roland Christen
 

I'm thinking more along the lines of older people who can't lift 40lb of mount any more, but could set up a smaller mount that weighs between 10 and 20 lb. The idea of the encoders was to eliminate doing PE correction. With a high resolution small scope and the tiny pixel cameras that can record 1.5 arc sec stars, the last thing you want is to have tracking variations over short time periods that measure 10 to 20 arc seconds. Yes, you could guide at rapid fire rates, but that's just more gear to take along.

As an example, last night I shot a huge number of 30, 60, 90, 120  second exposures of the core of M42 with the Mach2 encoder mount. I did not guide or model, simply let it gather data over a 4 hour period. The mount was just polar aligned with my usual techniques. The average FWHM of the stars was between 1.5 and 1.8 arc seconds. Total drift was around 30 arc seconds for the entire period ( 0.13 arc sec per minute). Although I used my CCD camera, a modern CMOS camera with a 120 second exposure can capture a lot of data. Perfect for a fun weekend camping trip where you set up the scope, let it do its thing while you enjoy friends around a campfire.

Rolando

-----Original Message-----
From: Bill Long <bill@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Fri, Feb 26, 2021 9:47 am
Subject: Re: [ap-gto] Small mount was Recent encoder discussion on CN

For visual use, wouldn't encoders be way overkill? 

For imaging mobile space is a serious concern, especially if you have a smaller car or when it is a family outing as well. Mount, counterweights, tripod, camera, wheel, guide accessories, imaging computer, cabling, backup supplies, tools, etc. Making the mount smaller and lighter helps a lot. Smaller and lighter tripod helps as well.

Taking imaging gear on a plane isn't really a need for me now, which is why the RST135 isn't in my gear herd yet. The AP400AE would be awesome and would work with all of my scopes except for the two big iDK scopes which I wouldn't likely take on a road trip anyhow.

For solo trips where the space is all mine to use, then my other mounts are fine. But boy would a nice light more compact mint be wonderful to have!


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Elenillor <elenillor@...>
Sent: Friday, February 26, 2021 5:38 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Small mount was Recent encoder discussion on CN
 
I will put in my 2 cents on this. Back in the day I put my name on the list for a 400 as I wanted a smaller mount to go with the 600E. I wound up with a Mach1 as the 400 was superseded by the larger mount and very glad I have it.
 
Still in the search for a smaller option I got a DM6 shortly after they were introduced. It was rarely used, and I eventually sold it.
 
The DM6 excursion taught me that the mount head is only a small part of the 'kit' that needs to be transported for portable observing. Having a small head really made no difference in ease of transport, setup or takedown. I am only visual, photographers have another whole set of 'kit' to deal with that is independent of the mount head. As a result I see no reason to make any tradeoff for a small head.
 
I assume an updated encodered 400 would be only a little less cost than and a Mach2. Would they sell in numbers big enough to justify it's development is a good question. That was apparently answered when the 400 was discontinued.
 
As an aside for grab and go I have a TEC110 F5.6 on a gear headed tripod. I take it in an out of the house almost daily for quick solar or night time viewing.  Also a SKY90 with a smaller tripod for suitcase travel.

John

On Thu, Feb 25, 2021 at 08:16 PM, Roland Christen wrote:
If we ever decide to design a smaller portable mount, what would be most desirable? What's missing in the panoply of mounts today? Before you answer, I have in my right hand a 400 mount that weighs 12lb without the base. It has a precision gear set and can be fitted with absolute encoders that would allow it to track at sub-arc sec levels. I daresay that this mount can easily swing a C11 or a 140 refractor. Is there a reason for such an animal?
 
Rolando

--
Roland Christen
Astro-Physics


Re: Recent encoder discussion on CN

Andrew Jones
 

On Fri, Feb 26, 2021 at 08:37 AM, Roland Christen wrote:
"Why would you ever release the lever to reposition the mount in the first place? Do you have a permanent setup such as a remote observatory system? In that case I cannot ever see why the mount would be moved manually. Do you have a temporary setup which you tear down after every session? In that case why would you care about knowing absolutely where the axes are pointed, since you will be starting off fresh anyway? Just loosen the clutches and place the mount in a known park position and start the session from there."
 
Rolando

Hi Roland.

Yes, my Mach1 is on a permanent pier in an Explora-Dome in my backyard. I have it setup so that I can image from the house and almost never have to go to the dome when imaging, However, I have a lot of other stuff one the mount like, focus controllers, dew heater controllers, USB hubs, etc. which I am always trying to refine the setup. When I am working on stuff during the day I will often reposition the scope so I can reach certain things easier. As you know with refractors, they will never be in balance unless they are in their imaging configuration with the focuser set to close to focus and the dew shield out. I don't put everything out in it's imaging configuration if I am just working on the mount or switching out other components. So when I am moving the mount it will never be perfectly balanced. I try to have a good hold on the OTA before I release the gearbox levers, but it can still move a bit. 
 


Re: Small mount was Recent encoder discussion on CN

Dale Ghent
 

On Feb 26, 2021, at 09:46, Frost David <frosty5@gmail.com> wrote:

I would love a smaller mount of this size and quality. It was what I wanted when I signed up for the Mach2 honestly. Something lighter and portable but still with great accuracy and same APCC/CP4 or 5 functionality.

This is why I recently purchased a Rainbow Astro 135. It weighs around 7 pounds and can easily be lifted out and setup on my tripod fully assembled in two minutes. For quick solar and nighttime use for those of us that do portable imaging, it’s fantastic. But the accuracy is nowhere near that of an AP mount. It physically can’t be. But for short focal lengths it works.
Yeah, I bought an RST-135 for mobile imaging on weekend trips and plane ride. I put a CFF 92mm f/6 frac on the top of it and it works exceedingly well, with the main parts of the setup split between a Nanuck roll-aboard hard case and ThinkTank Photo Shapeshifter backpack. On planes, the hard case with scope and imaging stuff goes in the overhead, the RST, laptop, and cables in the backpack go under the seat in front of me, and the tripod and power supply is in checked baggage. I haven't yet travelled to a place where there's no AC power for it and covid has nix'd travel for now, so I have some time to figure out a LiFePO4-based portable battery system that doesn't bust the airline rules regarding lithium batteries. The limit is watt-hours per battery, per person. It's me, my wife, and kid, so I can max out the usage by allotting everyone their own battery.

The thing that makes the RST-135 such a killer travel-friendly scope is its harmonic drive which obviates the need for counterweights for reasonable loads. As we know, counterweights can be half the mount's weight, or even more, so removing them from the picture makes airline transport such an easier task to contemplate.

So far I've taken the ensemble on 1 international flight (to central Mexico) and 1 US destination (SF bay area). The customs folks at QRO airport in Mexico were curious and amused by the gear, but I'm used to the exercise with customs officers having carried a lot of photo gear around the world.


Re: Recent encoder discussion on CN

Andrew Jones
 

Hi Bill.

Thanks for the feedback. That is basically what I have been doing. I currently have a TEC 140 on my Mach1 and I try to balance the OTA with the focuser racked close to where it should be in focus. However, as soon as I move the focuser with a fairly heavy camera and FW attached, then it will immediately be out of balance. I always rack the focuser all the way and pull in the dew shield in when I am not planning on using the mount so that OTA is shorter and I can cover the scope easier for storage. In this configuration the mount will always be out of balance. Based on what I read the other day, I thought that Roland was recommending to use the clutches to reposition the mount when it is not fully balanced in order to minimize the risk of damaging the worm gear. For the Mach1, this seems to make sense as it does not have encoders and as long as I unpark the mount from a known park position then the mount will not get lost. What is not clear to me now, is when I get the 1100 with AEL encoders here in a couple months, should I be using the clutches when repositioning the mount in order to avoid having the mount get lost. Maybe I am misunderstanding, but Roland's post here seemed to indicate that using the gearbox levers is the preferred method for repositioning a mount with encoders. 

Of course, I can still use the clutches with the 1100 and do the same thing as I do with the Mach1 and just unpark from a known park position, but then it would seem I am defeating the point of having the encoders and having the mount always know where it is pointing. The post from the other day seem to indicate that using the clutches is always the best way to reposition the mount unless I need to do find balance. This discussion seem to recommend the opposite when using a mount with encoders. I just want to make sure I fully understand the difference between the two methods of repositioning the mount and the pros and cons of each method. If I am using a refractor the mount will only be in balance when the focuser is set to near the the focus position and the dew shield is out. If I am just working on the scope when I am not imaging I normally don't set it to its imaging configuration so it will always be out of balance when I am just working on the mount during the daytime. I actually think I may have damaged the worm gear on my Mach1 as I am having difficulty guiding on the DEC Axis and considering sending it into AP to get it inspected. I want to make sure I am 100% clear on this topic so I don't damage the 1100 with encoders while at the same time taking full advantage of having a mount with encoders that never gets lost. 


Re: Recent encoder discussion on CN

Roland Christen
 


Do you recommend using the gearbox release lever to reposition the mount if your mount has encoders?
The question was "does the ENCODER mount lose position when you move the mount manually?" The answer is YES, if you use the clutches, NO if you use the gearbox lever. Locking the clutches and using the gearbox lever makes the mount similar to a Paramount - in other words it becomes a clutchless mount. This would be the way to make a permanent remote observatory system where you always want to know where the axes are pointed.

Why would you ever release the lever to reposition the mount in the first place? Do you have a permanent setup such as a remote observatory system? In that case I cannot ever see why the mount would be moved manually. Do you have a temporary setup which you tear down after every session? In that case why would you care about knowing absolutely where the axes are pointed, since you will be starting off fresh anyway? Just loosen the clutches and place the mount in a known park position and start the session from there.

Rolando


-----Original Message-----
From: Andrew Jones <andjones132@...>
To: main@ap-gto.groups.io
Sent: Fri, Feb 26, 2021 9:44 am
Subject: Re: [ap-gto] Recent encoder discussion on CN

Hi Roland.
 
Thanks for this explanation. However, I am now a bit confused again. This discussion would seem to recommend using the gearbox release levers when repositioning the mount. However, I took away from the below response to my question the other day related to using clutches vs the gearbox release that I should almost never use the gearbox release except for fine balancing in order to not risk damaging the worm teeth on the mount. This post now seems to indicate that if you don’t want your mount to get lost that you should use the gearbox release if your mount has encoders. So now I am confused again. Do you recommend using the gearbox release lever to reposition the mount if your mount has encoders? Maybe I am making this more complicated then it needs to be…
 
 
“Use the clutches when you want to manually move the scope around the sky (example: for visual sweeping of the Milky way). Use the clutches for placing the mount manually to one of the park positions during startup if you have moved the mount from a previous setup. use the clutches to get a rough balance in the two axes….”
 
“Loosen the Gearbox Release Levers only with the scope in Park3 positions. Releasing them in any other position could cause the gear teeth to rake across each other and possibly damage the worm teeth. The result will be poor guiding. Damaged teeth are expensive to fix. Use this method only for fine balance. If you don't need to do fine balance, don't release the lever.”

--
Roland Christen
Astro-Physics


Re: Encoders in the Mach2 vs 1100

Roland Christen
 

The error in an encoder mount is not periodic, so there is no real "periodic" error. The error tends to be a single smooth sine wave over a 24 hour period.

Rolando



-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Fri, Feb 26, 2021 8:22 am
Subject: Re: [ap-gto] Encoders in the Mach2 vs 1100

Thanks for the explanations Rolando. That clears it up a bit. Indeed resolution and accuracy are two different beasts...

What I was missing is the fact that the accuracy spec is for an entire revolution of the ring. I also had a somewhat hard time wrapping my head around the fact that the pitch of the ticks (or barcodes) is the same for any ring size (at 30 microns) and that its not giving any benefits in actual resolution (ticks per arc-sec). But reading further, I understood that the output resolution is not solely dependant on the mechanical aspect, but also on the encoding protocol used. 

So my understanding at this point is that even if the pitch is the same for every size of ring, hence giving more "barcodes" on larger rings, the readhead is nonetheless outputting a value that is limited by the characteristics of the serial protocol used (26 bits for the Mach 2, as you stated). 

I also understand that these figures of 0.16 and 0.12 arc-sec accuracy are theoretical and achievable only under hypothetical ideal conditions. 

From all this, should I also understand that the Mach2's stated native periodic error of 0.25 arc-sec (peak-to-peak) is also a per-hour figure or am I still missing some parts of the puzzle ? (Is periodic error the same as accuracy in this context with encoders ?)

Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Roland Christen via groups.io <chris1011@...>
Envoyé : 24 février 2021 19:41
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Encoders in the Mach2 vs 1100
 

I would have thought that a bigger ring gives more space to mark a higher number of "ticks", hence giving higher resolution and so accuracy...
Resolution is not the same as accuracy.

There are 2^26 individual addresses (67,108,864) that can be accessed in the RESA encoder, whether it is 75mm or 100mm. Therefore the resolution is the same for both rings.

The stated accuracy is a measure of how accurate the encoder is over a 24 hour period of revolution (360 degree total angle of rotation). For the 75mm ring, accuracy would be approximately +-3.82arcsec/24hr or 0.16 arc sec per hour of tracking. For the 100mm ring it would be 0.12 arc sec. per hour.

In reality one can never get the ring to have zero runout, so the practical accuracy will come in at perhaps +-0.5 arc sec per hour, more or less. So whether you have a 100mm ring or a 75mm ring, it makes no practical difference. Star motion due to atmospheric refraction will be an order of magnitude higher if you are anywhere but at the exact zenith.

The way the RESA works is not like any other encoder system. It does not read "ticks" the way an ordinary encoder does. It reads a barcode that is imprinted on the steel ring. The barcode is read over a fairly large circumference angle. The readhead is a miniature camera, not a photodiode that registers black and white tick marks. It's really quite revolutionary how it works, and it does work splendidly for telescope mounts.

Rolando




-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Wed, Feb 24, 2021 4:40 pm
Subject: Re: [ap-gto] Encoders in the Mach2 vs 1100

Hello Roland,

Your post made me take a quick look at Renishaw's spec for the Resolute extended temp encoder and I found two interesting observations (not related to the low temp version) which made me realize I'm probably missing something in my understanding of how the encoders actually works...

First, when we look at the following table, the "system accuracy" is increasing with the diameter of the ring (kind of opposite of what you stated earlier), which made sense to me since I would have thought that a bigger ring gives more space to mark a higher number of "ticks", hence giving higher resolution and so accuracy... So I assume the "system accuracy" of the encoder (which is defined as graduation + SDE by Renishaw) doesn't directly translate into the "tracking accuracy" of the mount.



Second observation, still looking at that table, the order of magnitude of that system accuracy seems to be more than ten-fold lower in comparison to the spec'ed tracking accuracy of the mount (+/- 3.82 arc-sec "system accuracy" for the 75 mm ring vs +/- 0.25 arc-sec "tracking accuracy" of the Mach2).

To explain these differences, my guess would be that some (gear/pulley) ratio somewhere does indeed make the tracking accuracy similar throughout the mount models and while at the same time increasing it by a factor of about 10X relative to the Renishaw's specs, but I wondered if there was more to it...

Am I lost in space ? 

Regards,
Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Roland Christen via groups.io <chris1011@...>
Envoyé : 24 février 2021 11:48
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : [ap-gto] Encoders in the Mach2 vs 1100
 
Hello Astronuts,

To clear up any confusion about mount encoders, both Mach2 and 1100/1600 use the same Renishaw RESA high resolution encoders. The main difference is that the ring diameter of the 1100/1600 mounts is 100mm, the Mach2 uses a 75mm ring. Resolution and accuracy is the same for all. The readheads are the same RESA readheads, except that they are matched to their respective diameters, so that the 75mm readheads cannot be used on the 100mm rings and vice versa.

Roland Christen
Astro-Physics Inc.

--
Roland Christen
Astro-Physics

--
Roland Christen
Astro-Physics

--
Roland Christen
Astro-Physics


Re: Recent encoder discussion on CN

dvjbaja
 

Some thoughts on small, portable mounts.  The ultimate in portability and load carrying capability is the Rainbow Astro RST-135.  Not inexpensive, but innovative with lots of potential.  For short focus telescopes the odd periodic error curve from the harmonic drive is correctable with a small, separate guidescope.  Can be run in EQ, or Alt-az configurations.  I love alt-az for the convenience of operation, eyepiece placement, and the lack of the dreaded mount flip. It would carry a Stowaway with little effort and most likely a 130 f/6.  Another to consider is Rowan Astronomy Atl-az, which has all the machinist qualities of an Astro-Physics Mach 1, but in an Alt-az package for visual.  Soon to be motorized! It's actually about the size of an AP 400.   I love my AP gear, but look around, there are some very high quality products out there as alternatives as Roland and company consider their next offering.  

 BTW, as an American, I absolutely hate the flood of cheap Chinese mounts, telescopes, and CMOS astro-cameras on the US market.  They are good mounts and cameras overall plus very affordable for folks getting started. It would seem our American companies have had to counter the flood and go the high end premium route to maintain market share and profitability. As someone who has managed a $6B portfolio of desktop PC's across all price points, I understand this well.  It's a complex world.  

-jg


On Fri, Feb 26, 2021 at 5:34 AM weihaowang <whwang@...> wrote:
On Fri, Feb 26, 2021 at 11:16 AM, Roland Christen wrote:
If we ever decide to design a smaller portable mount, what would be most desirable? What's missing in the panoply of mounts today? Before you answer, I have in my right hand a 400 mount that weighs 12lb without the base. It has a precision gear set and can be fitted with absolute encoders that would allow it to track at sub-arc sec levels. I daresay that this mount can easily swing a C11 or a 140 refractor. Is there a reason for such an animal?

I love to see a portable mount from Astro-Physics. However, before you go ahead and design one, you may want to ask what kind of portability you are aiming at.

Portable with a car? Then I think Mach2 fits it nicely. Mach1 is even better I suppose, but there is a tradeoff in payload.

Portable for air travel? Then Mach2 is too heavy for that for most people. Even Mach1 may be too heavy. I think a compact design with 20lb of weight (including base and counterweight shaft) would be desirable for this. It will need a light-weight dovetail system.  The counterweight shaft needs to be thinner, and longer too, so people don't need to bring many heavy counterweights to the plane.  

For those who do this kind of portable imaging, do they need high-prevision absolute encoders?  I am not sure.  At least for me, I don't need.  A smooth PE curve with less than +/- 4" of amplitude will be sufficient for me (good enough for 5 minutes of exposures on 300mm lenses).  Even +/-8" would be acceptable if there is good permanent PEC.  The mount has to be rigid, in case the places we travel to is windy, but I think AP mounts are all good for this.  The polar scope may need some rethinking.  The current RAPAS may be a bit too bulky for such a small mount.  Finally, its power consumption needs to be as small as possible.

That's my wishlist for an air-portable mount.

Cheers,
Wei-Hao

--

Homepage:

http://www.asiaa.sinica.edu.tw/~whwang/

Astrobin gallery:
http://www.astrobin.com/users/whwang/


Re: Recent encoder discussion on CN

alan.dang@...
 

Sign me up and take my money.  Sounds like Bill would be #1 on the list and I would be #2. :)

1) although there are other mounts with similar carrying capacity, made outside the US, that are popular, as you have pointed out in another post, tracking at sidereal isn’t enough for perfection.  You also need modeling.  Having something that stops at 20kg carrying capacity works for someone who has scaled down their OTAs as well.  But really, it is being able to take advantage of the premium software and reliable electronics.

2) My assumption is that encoders are expensive but adding another product line will give you more negotiating power to get better individual unit pricing.  This can benefit AP profit margins across the entire encoder-enabled product line. 

Of course, there is a big backlog of Mach2 orders, so I guess you would have to imagine this new mount as the Stowaway which hopefully would be easier to manufacture compared to the Mach2.  Perhaps metal 3D printing for components that typically require complex machining is an option?  (I can actually help with that).

3) As a personal story, after 8 years on the list for the 130, I got the call for this current round last year.  I put my deposit down but with COVID, I later asked to be put back at the end of the line and to let someone else get their scope new and to get a refund.  We all know that AP130’s can resell for above purchase price - but I thought it was important to honor the intent of the notification list and spirit behind it.  A friend with multiple AP optics offered to sell his EDF6 to me.  I took his offer up, knowing that I was giving up QuadTCC upgradability and has to find a “leftover” flattener in Poland.

Since then, there is now talk of recreating flatteners for other 130EDF6 owners given the difference in imaging today versus when the 130EDF was current.  Now, there is now talk of even a QuadTCC compatible with the original EDF6.

This story highlights your customer service at AP.  Buying into this new mount means that we are also buying into this ecosystem and culture of quality and community.

4) The Harmonic drive mounts are coming in at $4k for 13.5 kg carrying capacity and $8500 for 30kg capacity.  These have poor tracking performance but good guiding performance.  But they are lightweight.  

They are unique products, but they’re not 100% reliable and there are design choices like upward facing electrical ports that are at risk for dew damage.  

People are willing to pay a price premium over other 13-30kg capacity mounts and deal with poor tracking because it is convenient with counterweight free options.

The theoretical 20kg capacity puts you in between that price point and in between in price.  Like the Harmonic Drives, you are paying extra compared to others.

Instead of extra convenient as the rationale for the price premium, the rationale for this mount is extra reliability (as you mention being able to hot plug cables without damage) and AP feature set for the software and proven on-going customer focused policies and support. 


Re: Small mount was Recent encoder discussion on CN

Bill Long
 

A 400AE mount would be incredible for use with the Stowaway and GTX. I'd be all over that and that would make driving over Snoqualmie Pass to get to better skies a much less labor intensive packing job!


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of W Hilmo <y.groups@...>
Sent: Friday, February 26, 2021 7:40 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Small mount was Recent encoder discussion on CN
 

I would be interested in a smaller Astro-Physics mount.

 

In terms of size, I would want to be able to carry my 130 GTX for imaging.  That would allow me to leave my big Astro-Physics mount at home when I travel to dark sky sites 4 or 5 times per year.  The smaller the mount, the better, as long as it meets this performance criteria.

 

In terms of price, I would want to see the mount, equipped for use with counterweights, pier, dovetail plates, etc., come in somewhere below a similarly equipped MyT.

 

In terms of features, I would love to have a baby Mach2, with identical features.  I just don’t think that’s possible at the price target above, due to the encoders, but I think that’s OK.  If you could build a 40lb capacity version of the Mach1, with performance to match the Mach1, I think that would be a sweet mount.  It would also be a logical entry for folks looking to step up into a premium mount.  I know that I’d be all over it.

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Frost David
Sent: Friday, February 26, 2021 6:46 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Small mount was Recent encoder discussion on CN

 

I would love a smaller mount of this size and quality.  It was what I wanted when I signed up for the Mach2 honestly.  Something lighter and portable but still with great accuracy and same APCC/CP4 or 5 functionality.

 

This is why I recently purchased a Rainbow Astro 135.  It weighs around 7 pounds and can easily be lifted out and setup on my tripod fully assembled in two minutes.  For quick solar and nighttime use for those of us that do portable imaging, it’s fantastic.  But the accuracy is nowhere near that of an AP mount.  It physically can’t be.  But for short focal lengths it works.

 

A small lightweight AP mount like this with encoders that could carry a C11 would track great and be a game changer for small lightweight portable mounts.  150lbs of gear for the Mach2 (mount, counterweight, CW bar, pier, etc) is not exactly as portable though it does fit fine in a car.  If a 10-12lb mount could do the same job of carrying a 140mm refractor or a C11 just as accurately, that would be killer.  Just miniaturize the Mach2.

 

David

 



On Feb 26, 2021, at 7:38 AM, Elenillor <elenillor@...> wrote:



I will put in my 2 cents on this. Back in the day I put my name on the list for a 400 as I wanted a smaller mount to go with the 600E. I wound up with a Mach1 as the 400 was superseded by the larger mount and very glad I have it.

 

Still in the search for a smaller option I got a DM6 shortly after they were introduced. It was rarely used, and I eventually sold it.

 

The DM6 excursion taught me that the mount head is only a small part of the 'kit' that needs to be transported for portable observing. Having a small head really made no difference in ease of transport, setup or takedown. I am only visual, photographers have another whole set of 'kit' to deal with that is independent of the mount head. As a result I see no reason to make any tradeoff for a small head.

 

I assume an updated encodered 400 would be only a little less cost than and a Mach2. Would they sell in numbers big enough to justify it's development is a good question. That was apparently answered when the 400 was discontinued.

 

As an aside for grab and go I have a TEC110 F5.6 on a gear headed tripod. I take it in an out of the house almost daily for quick solar or night time viewing.  Also a SKY90 with a smaller tripod for suitcase travel.

John

On Thu, Feb 25, 2021 at 08:16 PM, Roland Christen wrote:

If we ever decide to design a smaller portable mount, what would be most desirable? What's missing in the panoply of mounts today? Before you answer, I have in my right hand a 400 mount that weighs 12lb without the base. It has a precision gear set and can be fitted with absolute encoders that would allow it to track at sub-arc sec levels. I daresay that this mount can easily swing a C11 or a 140 refractor. Is there a reason for such an animal?

 

Rolando


Re: Recent encoder discussion on CN

Bill Long
 

If you've balanced the mount properly then there shouldn't be any risk with the gearbox lever. 


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Andrew Jones <andjones132@...>
Sent: Friday, February 26, 2021 7:44 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Recent encoder discussion on CN
 

Hi Roland.

 

Thanks for this explanation. However, I am now a bit confused again. This discussion would seem to recommend using the gearbox release levers when repositioning the mount. However, I took away from the below response to my question the other day related to using clutches vs the gearbox release that I should almost never use the gearbox release except for fine balancing in order to not risk damaging the worm teeth on the mount. This post now seems to indicate that if you don’t want your mount to get lost that you should use the gearbox release if your mount has encoders. So now I am confused again. Do you recommend using the gearbox release lever to reposition the mount if your mount has encoders? Maybe I am making this more complicated then it needs to be…

 

 

“Use the clutches when you want to manually move the scope around the sky (example: for visual sweeping of the Milky way). Use the clutches for placing the mount manually to one of the park positions during startup if you have moved the mount from a previous setup. use the clutches to get a rough balance in the two axes….”

 

“Loosen the Gearbox Release Levers only with the scope in Park3 positions. Releasing them in any other position could cause the gear teeth to rake across each other and possibly damage the worm teeth. The result will be poor guiding. Damaged teeth are expensive to fix. Use this method only for fine balance. If you don't need to do fine balance, don't release the lever.”


Re: Small mount was Recent encoder discussion on CN

Bill Long
 

For visual use, wouldn't encoders be way overkill? 

For imaging mobile space is a serious concern, especially if you have a smaller car or when it is a family outing as well. Mount, counterweights, tripod, camera, wheel, guide accessories, imaging computer, cabling, backup supplies, tools, etc. Making the mount smaller and lighter helps a lot. Smaller and lighter tripod helps as well.

Taking imaging gear on a plane isn't really a need for me now, which is why the RST135 isn't in my gear herd yet. The AP400AE would be awesome and would work with all of my scopes except for the two big iDK scopes which I wouldn't likely take on a road trip anyhow.

For solo trips where the space is all mine to use, then my other mounts are fine. But boy would a nice light more compact mint be wonderful to have!


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Elenillor <elenillor@...>
Sent: Friday, February 26, 2021 5:38 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Small mount was Recent encoder discussion on CN
 

I will put in my 2 cents on this. Back in the day I put my name on the list for a 400 as I wanted a smaller mount to go with the 600E. I wound up with a Mach1 as the 400 was superseded by the larger mount and very glad I have it.

 

Still in the search for a smaller option I got a DM6 shortly after they were introduced. It was rarely used, and I eventually sold it.

 

The DM6 excursion taught me that the mount head is only a small part of the 'kit' that needs to be transported for portable observing. Having a small head really made no difference in ease of transport, setup or takedown. I am only visual, photographers have another whole set of 'kit' to deal with that is independent of the mount head. As a result I see no reason to make any tradeoff for a small head.

 

I assume an updated encodered 400 would be only a little less cost than and a Mach2. Would they sell in numbers big enough to justify it's development is a good question. That was apparently answered when the 400 was discontinued.

 

As an aside for grab and go I have a TEC110 F5.6 on a gear headed tripod. I take it in an out of the house almost daily for quick solar or night time viewing.  Also a SKY90 with a smaller tripod for suitcase travel.

John

On Thu, Feb 25, 2021 at 08:16 PM, Roland Christen wrote:
If we ever decide to design a smaller portable mount, what would be most desirable? What's missing in the panoply of mounts today? Before you answer, I have in my right hand a 400 mount that weighs 12lb without the base. It has a precision gear set and can be fitted with absolute encoders that would allow it to track at sub-arc sec levels. I daresay that this mount can easily swing a C11 or a 140 refractor. Is there a reason for such an animal?
 
Rolando


Re: Recent encoder discussion on CN

Andrew Jones
 

Hi Roland.

 

Thanks for this explanation. However, I am now a bit confused again. This discussion would seem to recommend using the gearbox release levers when repositioning the mount. However, I took away from the below response to my question the other day related to using clutches vs the gearbox release that I should almost never use the gearbox release except for fine balancing in order to not risk damaging the worm teeth on the mount. This post now seems to indicate that if you don’t want your mount to get lost that you should use the gearbox release if your mount has encoders. So now I am confused again. Do you recommend using the gearbox release lever to reposition the mount if your mount has encoders? Maybe I am making this more complicated then it needs to be…

 

 

“Use the clutches when you want to manually move the scope around the sky (example: for visual sweeping of the Milky way). Use the clutches for placing the mount manually to one of the park positions during startup if you have moved the mount from a previous setup. use the clutches to get a rough balance in the two axes….”

 

“Loosen the Gearbox Release Levers only with the scope in Park3 positions. Releasing them in any other position could cause the gear teeth to rake across each other and possibly damage the worm teeth. The result will be poor guiding. Damaged teeth are expensive to fix. Use this method only for fine balance. If you don't need to do fine balance, don't release the lever.”


Re: GTOCP4 Control Box

Seb@stro
 

That's a nice compact obs you have there, Tom. 

Would be interested seeing the inside as well... What NUC model do you use ? Is it a rugged type ? I like your idea of the goldenrod heaters. I suppose once the NUC has warmed up and booted, it pretty-much self-heats for the rest of the night. Have you tested at -20 Celsius and the like? Maybe a bit off-topic here, sorry about that...

At my location (about 15 km North of Quebec City, in the mountains) I pretty much get temps of -15 to -25C all winter long (Brrr). But when the sky clears, I feel like I'm floating in space, which obviously I am on that little rock called Earth... 🤓

Clear skies!
Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Tom Blahovici <tom.va2fsq@...>
Envoyé : 24 février 2021 20:45
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] GTOCP4 Control Box
 
Hi Donald,
This is my setup.  Since you have a ROR setup you have a lot more space than me.
My mount is still an older AP600 but it has the latest CP4 controller. If you look at the picture of my "observatory",  you will see a little box to the left of the observatory under the wood platform.  In there is a 12V power supply, an Ethernet hub, and an IOT power bar.
The Ethernet hub connects to an I5, Intel NUC running Windows 10 Pro and is accessible via Remote Desktop. The NUC has a few USB ports and one connects to a hub mounted on the telescope itself.  The hub provides connectivity to an ASI6200mm, filter wheel, an ASI290mm off axis guider, and a Moonlight Nitecrawler focuser.
The CP4 itself uses an ethernet connection from the hub.  The NUC is very versatile and also has a Thunder bolt interface.  I use that with a Thunderbolt to 10G ethernet adapter.  Gives me 10 times the throughput of a standard gigabit Ethernet connection.  Pretty useful with the 125Mbyte images of the ASI6200.
The NUC is really good.  Will last a long time.
My observing session goes like this:  I turn on the computer and equipment remotely using my IOT phone app to let it warm up and get ready. This connection also has a couple of heaters (Golden Rod heaters to keep the "observatory" warm. These are then turned off).  I go outside, unlock the cover to my Observatory and lift off the cover.  It is made of foam and aluminum angle strips and weights 15 pounds. It is covered in Dacron, and filler (same material used for aircraft wings) and is super durable (6 years and counting with Montreal weather).  I then go inside, connect to the NUC with Windows remote desktop, Open APCC, connect to the mount, and start Voyager.
Running in 5 minutes.  Can't wait until it's housing an Ap 1100
Tom


Re: Small mount was Recent encoder discussion on CN

W Hilmo
 

I would be interested in a smaller Astro-Physics mount.

 

In terms of size, I would want to be able to carry my 130 GTX for imaging.  That would allow me to leave my big Astro-Physics mount at home when I travel to dark sky sites 4 or 5 times per year.  The smaller the mount, the better, as long as it meets this performance criteria.

 

In terms of price, I would want to see the mount, equipped for use with counterweights, pier, dovetail plates, etc., come in somewhere below a similarly equipped MyT.

 

In terms of features, I would love to have a baby Mach2, with identical features.  I just don’t think that’s possible at the price target above, due to the encoders, but I think that’s OK.  If you could build a 40lb capacity version of the Mach1, with performance to match the Mach1, I think that would be a sweet mount.  It would also be a logical entry for folks looking to step up into a premium mount.  I know that I’d be all over it.

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Frost David
Sent: Friday, February 26, 2021 6:46 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Small mount was Recent encoder discussion on CN

 

I would love a smaller mount of this size and quality.  It was what I wanted when I signed up for the Mach2 honestly.  Something lighter and portable but still with great accuracy and same APCC/CP4 or 5 functionality.

 

This is why I recently purchased a Rainbow Astro 135.  It weighs around 7 pounds and can easily be lifted out and setup on my tripod fully assembled in two minutes.  For quick solar and nighttime use for those of us that do portable imaging, it’s fantastic.  But the accuracy is nowhere near that of an AP mount.  It physically can’t be.  But for short focal lengths it works.

 

A small lightweight AP mount like this with encoders that could carry a C11 would track great and be a game changer for small lightweight portable mounts.  150lbs of gear for the Mach2 (mount, counterweight, CW bar, pier, etc) is not exactly as portable though it does fit fine in a car.  If a 10-12lb mount could do the same job of carrying a 140mm refractor or a C11 just as accurately, that would be killer.  Just miniaturize the Mach2.

 

David

 



On Feb 26, 2021, at 7:38 AM, Elenillor <elenillor@...> wrote:



I will put in my 2 cents on this. Back in the day I put my name on the list for a 400 as I wanted a smaller mount to go with the 600E. I wound up with a Mach1 as the 400 was superseded by the larger mount and very glad I have it.

 

Still in the search for a smaller option I got a DM6 shortly after they were introduced. It was rarely used, and I eventually sold it.

 

The DM6 excursion taught me that the mount head is only a small part of the 'kit' that needs to be transported for portable observing. Having a small head really made no difference in ease of transport, setup or takedown. I am only visual, photographers have another whole set of 'kit' to deal with that is independent of the mount head. As a result I see no reason to make any tradeoff for a small head.

 

I assume an updated encodered 400 would be only a little less cost than and a Mach2. Would they sell in numbers big enough to justify it's development is a good question. That was apparently answered when the 400 was discontinued.

 

As an aside for grab and go I have a TEC110 F5.6 on a gear headed tripod. I take it in an out of the house almost daily for quick solar or night time viewing.  Also a SKY90 with a smaller tripod for suitcase travel.

John

On Thu, Feb 25, 2021 at 08:16 PM, Roland Christen wrote:

If we ever decide to design a smaller portable mount, what would be most desirable? What's missing in the panoply of mounts today? Before you answer, I have in my right hand a 400 mount that weighs 12lb without the base. It has a precision gear set and can be fitted with absolute encoders that would allow it to track at sub-arc sec levels. I daresay that this mount can easily swing a C11 or a 140 refractor. Is there a reason for such an animal?

 

Rolando


Re: Small mount was Recent encoder discussion on CN

DFisch
 

Rolando, when you get those encoders to put on the 400 mount I have one that I would love to retrofit.  it is such a delight to use on small set ups and enables carefree observation Tom fischer INDY

On Fri, Feb 26, 2021 at 08:38 Elenillor <elenillor@...> wrote:

I will put in my 2 cents on this. Back in the day I put my name on the list for a 400 as I wanted a smaller mount to go with the 600E. I wound up with a Mach1 as the 400 was superseded by the larger mount and very glad I have it.

 

Still in the search for a smaller option I got a DM6 shortly after they were introduced. It was rarely used, and I eventually sold it.

 

The DM6 excursion taught me that the mount head is only a small part of the 'kit' that needs to be transported for portable observing. Having a small head really made no difference in ease of transport, setup or takedown. I am only visual, photographers have another whole set of 'kit' to deal with that is independent of the mount head. As a result I see no reason to make any tradeoff for a small head.

 

I assume an updated encodered 400 would be only a little less cost than and a Mach2. Would they sell in numbers big enough to justify it's development is a good question. That was apparently answered when the 400 was discontinued.

 

As an aside for grab and go I have a TEC110 F5.6 on a gear headed tripod. I take it in an out of the house almost daily for quick solar or night time viewing.  Also a SKY90 with a smaller tripod for suitcase travel.

John

On Thu, Feb 25, 2021 at 08:16 PM, Roland Christen wrote:
If we ever decide to design a smaller portable mount, what would be most desirable? What's missing in the panoply of mounts today? Before you answer, I have in my right hand a 400 mount that weighs 12lb without the base. It has a precision gear set and can be fitted with absolute encoders that would allow it to track at sub-arc sec levels. I daresay that this mount can easily swing a C11 or a 140 refractor. Is there a reason for such an animal?
 
Rolando

--
TJF MOBILE


Re: Small mount was Recent encoder discussion on CN

Bill Long
 

The RST135 really fits the airplane carry on portable need well. The revived 400AE mount would be really great for trips where space is at a premium in your vehicle. You really want that performance and precision, and you're heading out with your 5" refractor but you don't want the whole vehicle filled with big cases, large tripod, etc. You also want to take other humans with you. Maybe a dog as well. They like food, clothes, and their own stuff too. Once you're there you find a really great spot to set up, but you'll need to hike a mild amount to get there. The size, weight, and capacity enable that scenario well. 


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Frost David <frosty5@...>
Sent: Friday, February 26, 2021 6:46 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Small mount was Recent encoder discussion on CN
 
I would love a smaller mount of this size and quality.  It was what I wanted when I signed up for the Mach2 honestly.  Something lighter and portable but still with great accuracy and same APCC/CP4 or 5 functionality.

This is why I recently purchased a Rainbow Astro 135.  It weighs around 7 pounds and can easily be lifted out and setup on my tripod fully assembled in two minutes.  For quick solar and nighttime use for those of us that do portable imaging, it’s fantastic.  But the accuracy is nowhere near that of an AP mount.  It physically can’t be.  But for short focal lengths it works.

A small lightweight AP mount like this with encoders that could carry a C11 would track great and be a game changer for small lightweight portable mounts.  150lbs of gear for the Mach2 (mount, counterweight, CW bar, pier, etc) is not exactly as portable though it does fit fine in a car.  If a 10-12lb mount could do the same job of carrying a 140mm refractor or a C11 just as accurately, that would be killer.  Just miniaturize the Mach2.

David


On Feb 26, 2021, at 7:38 AM, Elenillor <elenillor@...> wrote:



I will put in my 2 cents on this. Back in the day I put my name on the list for a 400 as I wanted a smaller mount to go with the 600E. I wound up with a Mach1 as the 400 was superseded by the larger mount and very glad I have it.

 

Still in the search for a smaller option I got a DM6 shortly after they were introduced. It was rarely used, and I eventually sold it.

 

The DM6 excursion taught me that the mount head is only a small part of the 'kit' that needs to be transported for portable observing. Having a small head really made no difference in ease of transport, setup or takedown. I am only visual, photographers have another whole set of 'kit' to deal with that is independent of the mount head. As a result I see no reason to make any tradeoff for a small head.

 

I assume an updated encodered 400 would be only a little less cost than and a Mach2. Would they sell in numbers big enough to justify it's development is a good question. That was apparently answered when the 400 was discontinued.

 

As an aside for grab and go I have a TEC110 F5.6 on a gear headed tripod. I take it in an out of the house almost daily for quick solar or night time viewing.  Also a SKY90 with a smaller tripod for suitcase travel.

John

On Thu, Feb 25, 2021 at 08:16 PM, Roland Christen wrote:
If we ever decide to design a smaller portable mount, what would be most desirable? What's missing in the panoply of mounts today? Before you answer, I have in my right hand a 400 mount that weighs 12lb without the base. It has a precision gear set and can be fitted with absolute encoders that would allow it to track at sub-arc sec levels. I daresay that this mount can easily swing a C11 or a 140 refractor. Is there a reason for such an animal?
 
Rolando


Re: Small mount was Recent encoder discussion on CN

Frost David
 

I would love a smaller mount of this size and quality.  It was what I wanted when I signed up for the Mach2 honestly.  Something lighter and portable but still with great accuracy and same APCC/CP4 or 5 functionality.

This is why I recently purchased a Rainbow Astro 135.  It weighs around 7 pounds and can easily be lifted out and setup on my tripod fully assembled in two minutes.  For quick solar and nighttime use for those of us that do portable imaging, it’s fantastic.  But the accuracy is nowhere near that of an AP mount.  It physically can’t be.  But for short focal lengths it works.

A small lightweight AP mount like this with encoders that could carry a C11 would track great and be a game changer for small lightweight portable mounts.  150lbs of gear for the Mach2 (mount, counterweight, CW bar, pier, etc) is not exactly as portable though it does fit fine in a car.  If a 10-12lb mount could do the same job of carrying a 140mm refractor or a C11 just as accurately, that would be killer.  Just miniaturize the Mach2.

David


On Feb 26, 2021, at 7:38 AM, Elenillor <elenillor@...> wrote:



I will put in my 2 cents on this. Back in the day I put my name on the list for a 400 as I wanted a smaller mount to go with the 600E. I wound up with a Mach1 as the 400 was superseded by the larger mount and very glad I have it.

 

Still in the search for a smaller option I got a DM6 shortly after they were introduced. It was rarely used, and I eventually sold it.

 

The DM6 excursion taught me that the mount head is only a small part of the 'kit' that needs to be transported for portable observing. Having a small head really made no difference in ease of transport, setup or takedown. I am only visual, photographers have another whole set of 'kit' to deal with that is independent of the mount head. As a result I see no reason to make any tradeoff for a small head.

 

I assume an updated encodered 400 would be only a little less cost than and a Mach2. Would they sell in numbers big enough to justify it's development is a good question. That was apparently answered when the 400 was discontinued.

 

As an aside for grab and go I have a TEC110 F5.6 on a gear headed tripod. I take it in an out of the house almost daily for quick solar or night time viewing.  Also a SKY90 with a smaller tripod for suitcase travel.

John

On Thu, Feb 25, 2021 at 08:16 PM, Roland Christen wrote:
If we ever decide to design a smaller portable mount, what would be most desirable? What's missing in the panoply of mounts today? Before you answer, I have in my right hand a 400 mount that weighs 12lb without the base. It has a precision gear set and can be fitted with absolute encoders that would allow it to track at sub-arc sec levels. I daresay that this mount can easily swing a C11 or a 140 refractor. Is there a reason for such an animal?
 
Rolando


Re: Encoders in the Mach2 vs 1100

Seb@stro
 

Thanks for the explanations Rolando. That clears it up a bit. Indeed resolution and accuracy are two different beasts...

What I was missing is the fact that the accuracy spec is for an entire revolution of the ring. I also had a somewhat hard time wrapping my head around the fact that the pitch of the ticks (or barcodes) is the same for any ring size (at 30 microns) and that its not giving any benefits in actual resolution (ticks per arc-sec). But reading further, I understood that the output resolution is not solely dependant on the mechanical aspect, but also on the encoding protocol used. 

So my understanding at this point is that even if the pitch is the same for every size of ring, hence giving more "barcodes" on larger rings, the readhead is nonetheless outputting a value that is limited by the characteristics of the serial protocol used (26 bits for the Mach 2, as you stated). 

I also understand that these figures of 0.16 and 0.12 arc-sec accuracy are theoretical and achievable only under hypothetical ideal conditions. 

From all this, should I also understand that the Mach2's stated native periodic error of 0.25 arc-sec (peak-to-peak) is also a per-hour figure or am I still missing some parts of the puzzle ? (Is periodic error the same as accuracy in this context with encoders ?)

Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Roland Christen via groups.io <chris1011@...>
Envoyé : 24 février 2021 19:41
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Encoders in the Mach2 vs 1100
 

I would have thought that a bigger ring gives more space to mark a higher number of "ticks", hence giving higher resolution and so accuracy...
Resolution is not the same as accuracy.

There are 2^26 individual addresses (67,108,864) that can be accessed in the RESA encoder, whether it is 75mm or 100mm. Therefore the resolution is the same for both rings.

The stated accuracy is a measure of how accurate the encoder is over a 24 hour period of revolution (360 degree total angle of rotation). For the 75mm ring, accuracy would be approximately +-3.82arcsec/24hr or 0.16 arc sec per hour of tracking. For the 100mm ring it would be 0.12 arc sec. per hour.

In reality one can never get the ring to have zero runout, so the practical accuracy will come in at perhaps +-0.5 arc sec per hour, more or less. So whether you have a 100mm ring or a 75mm ring, it makes no practical difference. Star motion due to atmospheric refraction will be an order of magnitude higher if you are anywhere but at the exact zenith.

The way the RESA works is not like any other encoder system. It does not read "ticks" the way an ordinary encoder does. It reads a barcode that is imprinted on the steel ring. The barcode is read over a fairly large circumference angle. The readhead is a miniature camera, not a photodiode that registers black and white tick marks. It's really quite revolutionary how it works, and it does work splendidly for telescope mounts.

Rolando




-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Wed, Feb 24, 2021 4:40 pm
Subject: Re: [ap-gto] Encoders in the Mach2 vs 1100

Hello Roland,

Your post made me take a quick look at Renishaw's spec for the Resolute extended temp encoder and I found two interesting observations (not related to the low temp version) which made me realize I'm probably missing something in my understanding of how the encoders actually works...

First, when we look at the following table, the "system accuracy" is increasing with the diameter of the ring (kind of opposite of what you stated earlier), which made sense to me since I would have thought that a bigger ring gives more space to mark a higher number of "ticks", hence giving higher resolution and so accuracy... So I assume the "system accuracy" of the encoder (which is defined as graduation + SDE by Renishaw) doesn't directly translate into the "tracking accuracy" of the mount.



Second observation, still looking at that table, the order of magnitude of that system accuracy seems to be more than ten-fold lower in comparison to the spec'ed tracking accuracy of the mount (+/- 3.82 arc-sec "system accuracy" for the 75 mm ring vs +/- 0.25 arc-sec "tracking accuracy" of the Mach2).

To explain these differences, my guess would be that some (gear/pulley) ratio somewhere does indeed make the tracking accuracy similar throughout the mount models and while at the same time increasing it by a factor of about 10X relative to the Renishaw's specs, but I wondered if there was more to it...

Am I lost in space ? 

Regards,
Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Roland Christen via groups.io <chris1011@...>
Envoyé : 24 février 2021 11:48
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : [ap-gto] Encoders in the Mach2 vs 1100
 
Hello Astronuts,

To clear up any confusion about mount encoders, both Mach2 and 1100/1600 use the same Renishaw RESA high resolution encoders. The main difference is that the ring diameter of the 1100/1600 mounts is 100mm, the Mach2 uses a 75mm ring. Resolution and accuracy is the same for all. The readheads are the same RESA readheads, except that they are matched to their respective diameters, so that the 75mm readheads cannot be used on the 100mm rings and vice versa.

Roland Christen
Astro-Physics Inc.

--
Roland Christen
Astro-Physics

--
Roland Christen
Astro-Physics


Re: Small mount was Recent encoder discussion on CN

Elenillor
 

I will put in my 2 cents on this. Back in the day I put my name on the list for a 400 as I wanted a smaller mount to go with the 600E. I wound up with a Mach1 as the 400 was superseded by the larger mount and very glad I have it.

 

Still in the search for a smaller option I got a DM6 shortly after they were introduced. It was rarely used, and I eventually sold it.

 

The DM6 excursion taught me that the mount head is only a small part of the 'kit' that needs to be transported for portable observing. Having a small head really made no difference in ease of transport, setup or takedown. I am only visual, photographers have another whole set of 'kit' to deal with that is independent of the mount head. As a result I see no reason to make any tradeoff for a small head.

 

I assume an updated encodered 400 would be only a little less cost than and a Mach2. Would they sell in numbers big enough to justify it's development is a good question. That was apparently answered when the 400 was discontinued.

 

As an aside for grab and go I have a TEC110 F5.6 on a gear headed tripod. I take it in an out of the house almost daily for quick solar or night time viewing.  Also a SKY90 with a smaller tripod for suitcase travel.

John


On Thu, Feb 25, 2021 at 08:16 PM, Roland Christen wrote:
If we ever decide to design a smaller portable mount, what would be most desirable? What's missing in the panoply of mounts today? Before you answer, I have in my right hand a 400 mount that weighs 12lb without the base. It has a precision gear set and can be fitted with absolute encoders that would allow it to track at sub-arc sec levels. I daresay that this mount can easily swing a C11 or a 140 refractor. Is there a reason for such an animal?
 
Rolando

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