tonyowens_uk

Nice piece of imaging Oskari. As these were taken well into the morning, i can see that altitude of both Mars and Jupiter was decently high for you - above 32 degrees! You obviously have excellent optics in your Newt to be turning in this level of detail from a 10" aperture, and you managed the focusing very well. As you mention, no contrast issues from the condensation on the diagonal, and nicely processed. Bravo!

My thoughts: At the very least, this instrument and its accessories should be offered to the UK Science Museum in Kensington (complete with installation support). If not, perhaps the Dublin Institute of Advanced Studies in Ireland might be interested in hosting it at Dunsink observatory. Dublin was the original home of Grubb & Son, predecessor of Grubb Parsons of Newcastle, the last great instrument builder of the UK with whom David Sinden was associated for a good part of his career.

You saw that patent too, good Andy! That, together with the motion control strategy and Dave Rowe's sky pointing modelling code have given 10Micron a huge pricing advantage in the market for professional-oriented mounts. But there are other routes to 23-24 bit angle encoding. I was an early user of Netzer Precision's capacitive encoder technology for precision automated assembly machines using a servo-controlled 'dial plate' and found their encoder easy to install without the ultra-precision positioning of read-head and engraved ring that optical encoders impose on assembly. Some of these capacitive, magnetic or inductive options offer high resolution 'on paper', even high repeatability, but it is hard to find non-optical techologies that offer actual accuracy anywhere near 23 bits. The Netzer encoders I believe they go to 21 bits repeatability, perhaps 22 bits (i.e., not enough), but the actual quoted accuracy was closer to 18 bits. Pricing per axis was comparable to your modular Heidenhains. There are other options from the UK and China that also are worth exploring, particularly Chinese options. I have a mount upgrade project starting soon that is likely to involve this FWIW.

Hi James. The home sensors for each axis have nothing to do with the encoders. Homing is done using optical gap sensors, and they are not vulnerable to dust or moisture ingress if this happens. These mounts have not been vulnerable to a mild amount of airborne dust and pollen since the 'Freedom Find' encoders Stuart1971 refers to were deleted with the updated EQ8-R and EQ8-Rh models. Tony

About Onstep I entirely agree Orlando. I once saw Onstep as a way of making precision imaging mounts for a variety of purposes without being locked into a commercial ecosystem such as Synscan, or Scitech which I have no influence on. While I love the fact that some ESP32-based printer controllers can be turned into 4-axis motion controllers for a telescope, I prefer to stick with traditional motion control architecture that uses separate motor drives and a step/direction interface. This should in principle make integration of closed loop steppers (integrated stepper/encoder/drive packs) or any other suitable motor technology possible, without need to refine the Onstep firmware. But it isnt clear to me, from the Onstep forum posts I have looked at, how to put together an Onstep firmware/hardware/ALPACA driver configuration that can do this. And why am I interested in doing this? For low friction mount types e.g. roller-drive friction mounts or staged or differential timing belt designs, microstepped steppers that can exploit the vast low cost industrial base of stepper-based motion will deliver excellent open-loop telescope pointing, with OK high speed dynamics (for most use-cases), provided autoguiding is being used for position loop closure. But for high friction mount types e.g. worm gearing, closed-loop axis control is required to consistently build a mount that will deliver RMS tracking good enough so that autoguiding is unnecessary. Given that no Onstep platform I am aware of currently supports at least two high-speed BISS interfaces that would support high resolution axis encoders, the only current way to provide closed loop motion with Onstep would be by using the step/direction interface and using a separate motor drive that has such an encoder interface. Or using integrated motors, as I mentioned. Or am I missing something?

The image attached of a remote imaging observatory in Norway shows what I mean. This total payload is 90Kg. The main saddle supports a 16" RC imager, with a 6" APO plus 22 Kg of trim weight on the auxiliary saddle. The canted pier eliminates possibility of a pier strike (always a risk with bulky payloads) regardless of sky pointing angle or image rotator position angle. This particular system isnt normally used visually. Backlash is negligible and autoguided tracking error is under 0.3 arcsecs in good seeing. This system is based on a humble EQ8-R. There is plenty of scope for adding more optical systems to the second saddle in due course!

Balancing that lot will need big weights. The mount will take the weight but there will be lots of complications. Starting with how that can all be attached to the standard saddle without a lot of flexure. It would obviously be far better to split the payload between two saddles but converting an EQ8 to have a second saddle in place of a counterweight bar is not cheap.

Of course they do, just think of Crayford's friction focuser and Dobson scopes of all sorts. But it seems to me that the majority of the equipment that is mass-produced is either durable memes (German equatorial mount, solid cylindrical-tubed OTA's, four-vaned spider designs, RC catadiioptrics, exquisitely detailed small APO's) or fast fashion (harmonic drive-based portable mounts, integrated camera-telescope products, carbon-fibre tripods etc). And that is unfortunate. Given the nature of the people involved in this hobby/business/profession, I would expect to see much more innovation that we do at present. For a while Astrosurf in France had a thing going where collaborating engineers basically developed various non-commercial devices that that collective felt would be useful, and in so doing they greatly pushed along the standards of equipment in Francophone amateur astronomy. Remote-controlled Ethernet switches. the MCMT stepper-driven GoTo mount, large lightweight Dob engineering, Shack-Hartmann testing on a budget, the Roddier test and so on all were developed by members of this collective, some of whose personal webpages were goldmines of information. While all these people were 'amateurs', the great majority were software or mechanical engineers, machinists, astrophysicists etc - and this was reflected in the quality of much of their projects. Then, lets not forget the greatest amateur of all, whose ideas had significant impact on the design and execution of the Palomar 200" scope which pushed the limits of technology of the 1930-1950 period. Russell W Porter!

I think there is a balance of rights Chris. The issues I raised are whether a manufacturer has a duty of care towards the owner of a 10-20 year old piece of equipment, whether he has a duty of disclosure of the knowledge that goes into its design and manufacture, whether it is sensible to encourage a person without relevant training and experience to try and "calibrate" it, and what value to assign to the design opinions of a person who was not a part of the product development process. From my own professional background I know that multistage friction mounts are not simple to make or to set up so that they run without swash, without roller tracking problems, and without bending the capstan rollers. Attempting to do this without access to the work instructions and necessary fixtures and gauges isnt sensible. Thats my opinion FWIW. Panagiotis is perfectly free to do whatever he wants with his mount. I hope he learns from the experience of dismembering it, much as I learned about engines when I was a teenager by dismembering my poor father's lawn mower, and later his car's engine! Haynes Manuals were in part a response the need to prevent monopoly of product repairs by manufacturers and their franchised service networks, as was harmonised OBD diagnostics and various pieces of legislation in trade blocs around the world. Anything that allows repair and reuse of a product is good, but the exercise needs to be balanced against the rights of the manufacturer to make a living and those of society to be safe from dangerous products and imaginary thinking. I dont know anything about Mr Mesu's "history" nor do I want to. I understand that his mounts have excellent functionality, and are reliable unless damaged or overloaded. And I commend any engineer who has the drive to commercialise a fundamentally better drive principle such as friction drive, though I recognise that they also have weaknesses which limit their use. Peace Tony Owens

With respect Panagiotis, you dont sound like you are equipped or informed to be reverse-engineering this mount, which you do on an internet forum. What is your objective in doing this? Why do you think that Mesu owes you something when you acquire a old mount far out of warranty, and proceed to dismantle it without factory support or training? Your views about the design decisions made by its developer, and how to track the rollers are your own. Have a bit of sense and find an affordable way to get your mount back to the man who developed it, and ask him to refurbish it.

This is an old thread. But... As a fellow engineer, I am a huge admirer of Mesu's friction drive technology, which is the core of the mount. Not everybody realises how much effort and cost goes into perfecting a transmission with so little error, then working out how to make it at a price point that a niche target market is able to pay. The electrical components fitted to the mount will evolve as the Chinese manufacturing and engineering powerhouse commercialises affordable absolute 26bit shaft encoders and integrated motor/drive packs that undercut the price/performance of Swiss/German manufacturers of skewed winding motor loveliness. Graphical motion language (GML) will reappear in the form of fashionable low-code multithreaded microcontroller-based motion app development. And these mounts will soldier on, with new more cost-effective brains and muscles. Obsolescence isnt a well-founded risk for modern classic designs.

Taken by a friend 10 miles up the road from here, 30 mins ago. Not seen anything like this at our latitudes, ever.

Perhaps someone has a source of industrial quality USB cables they can pass along? Specifically I'm looking for USB 3 Type A to Type B plug cabling designed for industrial environments. This is the opposite of consumer and office-grade cabling. So I need either silicone or polyurethane (not PVC) sheaths, either flat or circular section, gold plated contacts, 3-5m length, choice of straight or right-angled plugs. This is for permanent outdoor use hooking up imaging equipment in Wicklow's cold wet windy climate. Many thanks Tony Owens

Graeme if you are still interested contact me off list to discuss or speak with Grant or Rob at FLO about the EQ8 modernisation service. It’s not a kit BTW. The service is collect and return as the modifications require a tool room or R&D lab to perform properly. Tony Owens

Thanks Dave, thats a good thought. Tony

Does anyone know whether Philip Keller the optical design engineer and supplier of professional Wynne correctors is still in business? If anyone has contact information for Hr Keller or his business I'd appreciate a referral, thanks. Tony Owens

No. Dignify the discussion by reading my essay. All that to try make a case for: more thoughtfulness about terms like quality in highly engineered systems the avoidance of loose language and the lazy equation of cost with quality and to discourage the casual dissing of the work products of other people (e.g. Onstep) without evidence! Best Tony Owens

Hi newbie! I dont think its meaningful to speak of the quality of a motor or any other technical component in the abstract. A 200 step/rev hybrid stepper motor cant be compared to a brushed DC servomotor without looking at the context. If that is running an axis of a telescope mount, we are looking at torque vs speed characteristics, electrical efficiency, noise emission, 'cogging' behaviour, spindle positioning elasticity (drive stiffness), robustness, wear life, ease of packaging, ease of commissioning and reliability. And in this application no meaningful comparison is possible without also including the motor drive electronics, cabling, connectors and firmware. On one side we have Maxon/Scitech and industrial sealed connectors and screened cabling. On the other, we might have a Chinese generic 400 step/rev NEMA17 hybrid stepper driven by a Trinamics TMC2209 driver and commanded by Onstep running on a modern ESP32 embedded controller, with unshielded and unsealed motor wiring. Or it might be a similar controller board operating a Clearpath SDSK stepper-servo with 6400 tic embedded encoder via Onstep's step/direction interface, and wired with silicone-sheathed shielded cable and metal IP65-rated M12 multipole connectors. In terms of measured following error during tracking (motion quality), the difference between these three solutions may well be negligible. Autoguiding compensates perfectly for the lack of a high-resolution axis encoder on all of these solutions. The torque capacity superiority of the stepper solutions is irrelevant as input torque capacity of Mesu's friction drive will limit how much motor torque can be delivered. The speed advantages of the servo are irrelevant as the steppers can 'pull' higher overall transmission gearing if necessary. As the friction transmission is (as I understand) backdriveable, the efficiency of the stepper-based drivetrain may be more efficient if the mount spends significant periods held stationary. Or not, as the case may be. There will be no difference in noise emission when tracking between these mounts except for the servo's faint 20 kHz commutation whine. None of these systems will exhibit cogging behavior visible in images (provided the servo is properly tuned with a small 'deadband' of about +/- 2 encoder counts and provided the Trinamics driver running the simple stepper has plenty of drive current available). One big difference between the simple stepper system and the other two (servo and servo-stepper) might be drive (motor rotor) positioning stiffness. Whether far superior rotor stiffness of the latter solutions provides any benefit will depend on the amount of friction in the Mesu's transmission. As this is far lower than worm drive mounts, for example, it may well be that there is no perceptible difference. But in a worm drive mount, especially of the antibacklash type where drag friction is significant, a difference is likely to be apparent in rms guiding error. Another difference emerges when looking at ease of commissioning. The Scitech servo system needs careful tuning to obtain stability without micro-oscillation at tracking speed or sluggish response to positioning moves, which makes building the systems more involved. None of these systems (so far as i'm aware?) employ speed reduction gearheads so all should be equally reliable. The only one that is environmentally-sealed to normal industrial standards for outdoor use (advisable for remote-controlled observatories for example) would be the servo-stepper one I mentioned with waterproof connectors. So there you have it. There is a very big difference between the cost of these three systems, the Scitech one being most costly by far. This is easily explained by: the manufacturing economics of the relevant component suppliers the avoidance of the need to recoup very substantial R&D costs on the Onstep system which is a GPL development that is designed to run on COTS hardware the fact that there are multiple parties involved in the supply chain for Scitech which leads to greater margin-taking For many end-users, performance differences between these systems will not be apparent, meaning that there is no perceptible diffrence in 'quality'. For a minority of users who need the greater simplicity of repairs and maintenance of the stepper system e.g. remote controlled imagers, that might be a better choice for them. For another minority who are interested in remote satellite tracking and orbital parameter calculations and need high dynamics, a servo-stepper system might be their choice. And perhaps a few (like me) admire the form and finish and heritage of historical highly-engineered assets - for us, the existing Maxon/Scitech solution is also appealing. Tony Owens

Quality of a motor or a motion controller has little to do with its cost. Stepper motor and servo motor drive systems have their own strengths and weaknesses, and in some applications the motor technologies can be blended (servo-stepper). What matters is the motion quality delivered, and the reliability and maintenance requirements. There is no reason I can think of why a microstepped Mesu friction mount should not track as well as the Maxon skewed-rotor/Scitech model, particularly if closed-loop steppers (servo-stepper technology with embedded encoder) are chosen. You seem to suggest that the Onstep control software is inferior to Scitech's. Do you have evidence for this?

The owner of the Skywatcher brand, and Celestron Corp and various other entities, and of the patent portfolio underpinning Skywatcher gear and manufacturing processes is Nantong Schmidt. David Chen is still executive chairman. I toured the manufacturing and engineering facilities in Dec 2018 and they looked healthy and financially successful to me. Tony Owens

Hi Mike. I agree with you about combining PPEC with properly-refined autoguiding - I've never seen a clear benefit myself in the case of EQ8's. What works for me extemely well (using the original motor board/motors used in the original EQ8 and antibacklasg gears) is very frequent small corrections, with a predictive guiding algo from PHD2. With the much improved motor board that appeared with the mount refresh, the picture is likely to be different because of the more refined microstepping behaviour, and I havent investigated that yet. Re references to the 'under the hood' EQ8-specific investigations and improvements built into GSS, I suggest you search for contributions from Andrew Johansen in particular. cheers Tony Owens

Hi Mike, Three examples of differences in favour of GSS v. EQMOD are: 1. If you use the integral PPEC on the EQ8 or EQ8R, I believe that incoming autoguider move commands that coincide with a PPEC 'bin' transition are ignored, which negatively affects guiding accuracy. This happens with EQMOD controlling EQ8, due to a design flaw in the EQ8's firmware design. My understanding is that this also happens with the newer EQ8 firmware versions (cross-compiled for the STM32 that runs the EQ8 motion controller). In GSS there is a workaround. 2. Very short autoguide corrections sent to either EQ8 or EQ8R are executed very rapidly in GSS using GoTo moves. EQMOD has nothing comparable. 3. EQMOD is not in active development. GSS has at least three intermittently active developers and a growing user base You can read about the first two of these issues on the GSS forum I hotlinked in my earlier post, if interested. Best Tony Owens

Nigella if you have not already looked at GSS as an alternative to EQMOD for controlling your new EQ8R, it would be worthwhile. There is a discussion list for GSS here: https://gss.groups.io/g/main GSS is in active development (it was originally developed to work around some of the EQ8's limitations, which it does rather well) with meaningful new functionality still appearing. You will no doubt have a large list of issues to work through with your 12" imaging Newt on your new EQ8R to get it operating reliably at the expected performance level, but when you get that under control, best have a look at GSS. Tony

Most pro-sumer mounts use stepper motors driven in microstepping mode. In the case of the older Skywatcher models, e.g. EQ8, there is a definite motor torque benefit to using the highest drive voltage possible. For safety, a regulated power supply set to 15Vdc maximum with at least 5A capacity and preferably 10A is my recommendation. Use sensibly short cabling from the supply to the mount, with 16AWG stranded wire, or more. That will hold cable loss to 0.3V or so. The reason for maximising torque is that in tracking mode when microstepping is active, significant friction arises in properly set up worm gear drives. This causes a 'following error' to arise - a lag beween the commanded stepper motor shaft position and the actual position, to the detriment of tracking accuracy. Fortunately the effect is small, but it is there. Boosting torque reduces following error. Tony Owens

I need to qualify my comment Ken. The comparison would be against quality antibacklash worm gears, not fixed-centre gears. Remember that many traditional mounts have neither ground worm gears, nor precision-grade worm bearings, nor antibacklash provisions. And in some cases not even proper environmental sealing of the oily bits. There is a huge quality spread across the hundreds of models of worm geared mounts available. Tony