tonyowens_uk
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Posts posted by tonyowens_uk
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Hi Goran. Your point about the original EQ8 and the quality of guiding it provides is well made. I have modernised or refurbished a number of them and all provides around 0.5 arcsec RMS following error on each axis when they left.
Neither revised nor original EQ8 offer antibacklash gearing. Also, the original EQ8 used a badly designed clutch that directly caused minute deformations of the mount that manifested as image shifts and (for Declination axis) binding and run-out. The Declination shaft bearings can make this problem worse, as can other constructional details. But all of this is soluble, and if done properly the mount is very dependable.
The Freedom Find encoders were a piece of whimsy I believe. They can't be used during precision pointing such as imaging, and were aimed at casual visual users with a product mentality who stick with the Synscan control paddle. Those encoders never protected against pier crashes and contributed nothing to accuracy. Which given their tendency to deteriorate with moisture ingress into the Declination worm wheel shroud, was just as well!With proper sealing, updated clutches, steel shafts, precision bearings and an antibacklash Declination gear, an EQ8 controlled using Green Swamp server, (a modern alternative to EQMOD) will point and autoguide a 35 kg imaging payload for years, with excellent reliability.
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For those who have bought one of these but are not instrument design engineers, here are my thoughts. I happen to have designed and built very high resolution traction drives for special machines with similar accuracy requirements, though not for telescopes.
In friction mounts the weaknesses are:1. susceptibility to moisture and dust (affects the reduction ratio of the friction final drive
2. low output torque (this is limited by the maximum safe contact pressure at the friction final drive that does not result in indentation - I note the reference to ceramic material which is interesting). There is an implication for maximum out-of-balance torque that the instrument payload can present to the mount.
3. the 'biggie' is usually what happens when an overload occurs, e.g., bumping into the scope. Unless a very reliable overload clutch is incorporated into the drivetrain, the friction wheel and pinion will slip, creating a flat spot on the pinion and introducing periodic error.
4. if absolute encoders are used that are not on the axis of the instrument, then position accuracy will be good for short goto moves but there will be inaccuracy over long moves due to slip at the traction drive. So plate-solving and syncing may be required, adding to move time in application involving lots of point-to-point moves.
The norm when buying a costly and complex instrument from a new supplier is to review the proposed design in detail before commissioning the project to proceed. In this case, as can be seen by scrutinising the various stages of mechanical R&D in phill76's post, all of these issues appear to have been visited.
The concerns I would have are:1. whether the promoter had any real knowledge and experience of friction mounts at the point when he started commercialising his project, and perhaps more importantly, is he now an expert and a 'safe pair of hands' in the art of friction mounts?
2. what performance and specification does the current incarnation of this mount offer? What is the proposed maximum payload? What is the lowest natural frequency of vibration under that payload, when mounted as recommended? Are there provisions to wipe the surfaces of the contacting friction components to remove wear detritus? How effective is the sealing? What are the overload clutch arrangements? What is the max slewing speed, and worst-case following error? How much backlash is there on each axis? (the motors use high reduction gearheads - what is their spec?) Is the mount documented? Does it come with the servomotors tuned?
3. what sort of ongoing maintenance is needed? How is that to be delivered? What are the warranty terms? For how long are custom parts going to be available as spares (e.g. pinions and wheels)?
If I was in the market for one of these, I would be looking for a free evaluation unit (sale or return) so I could evaluate the answers to some of these questions - which I would be fairly confident are not currently available from the promoter.
As for Louis Mesu and his designs - I have the impression that his mounts reflect a lifetime of obsessive development of friction mounts and precision instruments, not just for astronomers but also for large engineering businesses in NL. He is arguably the definitive 'safe pair of hands'.Tony Owens
14 hours ago, phill76 said:Hi all.
I have been watching this thread for some time now and due to my involvement i have tried to keep quiet and not upset the apple cart.
Newbie alert was talking about me when he says he has a mate that had paid in full for its a very very long story and 63 emails later i still don't have my mount.
In all fairness to Mark. i completely understand his issues and i have spoken with him on the phone about this whole saga and also what's been said in here and a few other places and he is aware and trying to do something about it.
So way back in March, i saw this mount on their website and thought i like the looks of this, all looked great. I first did some googling,found a few concerning posts/threads, like this one and i decided to email JTW and we started discussing the mount (OGEM) it was called back then. We spoke about these forum posts and i was reassured that the mount was all go and in production and he sent me a load of images of the parts etc.
Now i am a spur of the moment guy, i see something and if i want it then i want it and then my mind is set, i was convinced it was all good. I had a few issues with cash and i wanted so i decided to just go WTH and stuck it on my credit card. (oh dear i hear you all say)
i though thats fine i will just pay that off over a year and its not that bad. Anyways, Paid. i think £3900 and was told delivery just after ATT which was May 17th i think. well that date rolled by and i started thinking wheres my mount and i had a lot of thoughts of what to do, i emailed, got no response for ages until i sent a strongly worded email and was then told another date in July and on it went. I ended up completely loosing my temper at Mark and lots of emails back and forth and he explained all the issues they were having and i explained the complete lack of communication was abysmal and i was at a point of wanting my cash back.
Mark kindly agreed to fully upgrade "my" mount for free as i had only paid for the basic one, That's all i could afford. My argument was that he had sold me a mount that was as i suspected from the start as still in development and i was basically an early bird adopter that had paid full price . . He added me to the general mailing list for the "early birds" and in fairness to him, the communication got much better. there was times where we went 2 months with no updates and again he got a crappy email from me detailing my displeasure and in the end we had a phonecall and i will get to the end of this soon.
I personally think that Mark should never have taken my money when he did almost 1yr ago to the day and just said that the early birds are all sold out and i would have to wait. I can see why he did and he kinda took a gamble rather than loose a customer. his gamble was that he thought the OGEM was almost ready when truth be told as soon as they started testing they came upon massive problems and their own cost which has most likely put massive strain on him and his team for cashflow and upholding their promises to the early birds and ME, their first actual paying customer of this mount.
i see lots of negative comments in here and at the end of the day, the only people that really and truthfully have the right to complain are those of us that have parted cash and i don't think there is one in this whole thread until now that has stood up.
I think Mark and his team are doing a great job in bringing a new mount to our community that can only help drive prices down for all. It's unfortunate all the time and miscomunications , some might say lies but i think put yourselves in his shoes and then mine. I paid 4k on a credit card, i am still paying it off now so its over 5k easily it's cost me and yes i could have just got a Mesu for that but i am just thankful that it is coming to an end and i will finally get to enjoy my mount.
So i had an email yesterday. The mounts are coming to completion and i will post the whole email under this to show.
Greetings everyone!
Ok here goes…
It’s finally done!
Glad that’s out the way but seriously this one, after some final touches, is leaving on Friday to be installed. I'll send you pictures once it's installed with all the accompanying tracking graphs, pictures of the night sky and star shapes from 1800s subs etc. Suffice to say it works and tracks like a dream.
This was what you all purchased way back in the distant past, if your memories can stretch back that long -
This is where we are now, yes you may have invested in an OGEM but this is about as far removed from an OGEM as chalk and cheese. I am not going to bore you with the bumpy road we've all had to get to this point, as we all are painfully aware of the timescales and bruises we carry.
Once this mount is installed and I have done as I said above, I will begin shipping
As much as I have kept you waiting when it arrives and your happy please please post pictures of the mount and images you take as this project has nearly killed me to get to this stage and although some of you are paved your help once you are happy would be much appreciated.
Humble thanks
MarkI have been told that i am not getting this version but the full on production version and he has sent me an image but also asked me not to share it about just yet so i feel that my patience will be paid off.
This is my first post in here, I have long been a member of this forum but i don't normally get involved except this project affected me quite a lot and although i have held back a few times from posting my frustration and now feel that it was the right time to say something.
I honestly feel that JTW are really on to something here and they like any developer have had to spend the time to get it right. yes their reputation may be tarnished by all these delays but once the mounts start getting turned out and the reports come back good ( because they have spent the time ironing issues out) that their reputation will soon be turned around and it may make other crazy expensive manufacturers start to look at their prices.
The only thing they really did wrong was sell a mount to me ( i dont know is they have sold any others like me) because the rest were early birds paying a far cheaper price and knowingly getting involved in pretty much a "kickstarter" campaign so with them you pay, and you wait.
Im sure this post will spark many debate but i had to come and tell you of my sometimes really annoying year but also the good that should come of it.
Kind regards
Phill
http://www.facebook.com/buck1andAstro/
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FWIW I'll add my own experience of getting stuck in the firmware update loop with an AZGTi and how it was resolved. My unit was on firmware rev. 3.12 and never updated. After a rebuild I tried to flash it to the current non-EQ version, which is 3.20, using the Synscan Pro app on an iPhone, across the wifi link to the AZGTi. The flash failed part-way through, and foolishly I cycled the power as instructed by the MCU update app, and tried again. The AZGTi would now only broadcast the ID "ESP_xxxxxx" instead of the ID "Synscan_5227" I had previously seen from my unit. The LED was cycling through three quick flashes, i.e., the MCU was still in update mode. I couldn't connect and further power cycling made no difference.
I tried connecting using PC Direct Mode with my Synscan V4 handpad, but did not have either an RJ12 to RJ45 adapter or the time to make one up. So I bought the Skywatcher Wifi Adapter kit, which has one of these.
After this arrived, I put the AZGTi on a 12VDC feed, connected the new wifi adapter using Skywatcher's RJ12 to RJ45 adapter and looked for a new Wifi connection. The only one available was still the one being broadcast be the AZGTi's MCU, i.e., ESP_xxxxxx. The Skywatcher wifi adapter was clearly getting power from the AZGTi but there was no 'heatbeat' LED.So I gave up on the new wifi adapter and just used the RJ12 to RJ45 adapter cable to connect my Synscan paddle to the AZGTi serial port, connected the paddle to a laptop using a serial-to-USB adapter (with FTDI chip), setup PC Direct Mode on the Synscan paddle, and tried to connect from the PC to the MCU using Skywatcher's MCFirmwareLoader.exe v 1.74_nonwifi. I selected PC Direct Mode on the app and manually selected the correct COM port to use on the PC. No dice. The app could not find an MCU.
Finally, expecting to have to replace the AZGTi MCU with a new one, I decided to give the Skywatcher Synscan Relay Mode v4 a try. This turns the paddle into a simple transciever between an RS232 connection to a PC and the TTL level serial comms to the AZGTi MCU across its Hand Paddle port. So I first flashed my V4 paddle with SynscanRelay_V4_4.2 firmware, which was uneventful, then cycled the power on the mount (and thus the paddle) to boot up the transciever firmware. On trying to connect to the AZGTi with the MCU update app, the currently-loaded firmware could not be read, as before. But I linked the v3.20 firmware, and tried to update the MCU anyway. I was surprised to see this now went smoothly, and after power cycling the AZGTi on completion, restored to me a working mount.
As a final step I re-flashed the paddle to the current version of Synscan firmware. I very rarely use the paddle for mount control but find it occasionally useful for verifying reliable comms to Skywatcher mounts where I doubt the health of the MCU board.
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Hi Andy and thanks for your most interesting post. Your Astro-related activity level over your life as you describe it is actually very typical for a professional person!
The overall impression I got from your post was: ‘here is a chap who wants to “boil the ocean”, but do I really believe that is necessary? Ummm - no!’
ASCOM modularity allows even simple amateur telescope and instrument control to be simplified and maintained more easily. As TCS’s have bloated in the last two decades this modularity and ability to keep the bits that work and in which people have invested learning time is important.My suggestion would be to first look hard at what is wrong with other more developed telescope mount controller products and open source projects before doing anything more. I’d be particularly critical about conflating cost-driven Reprap technology from 3D printing with performance driven tech as needed in credible imaging mounts to be used in cold damp environments by elderly people of widely varying abilities! Cast a cold, critical eye on what you see.
Some practical points:
1. You would be very brave to take this on, alone. But some of the finest engineers on this planet are involved with Open source astro engineering projects and getting their assistance would be wise
2. Be careful about stepper motor technology in telescope tracking applications where both position and rate control are critical. In the real world, microstepping a common bipolar step motor does not increase the positioning resolution of a motion system by anything like x256 times, due to low rotor stiffness, constructional and phase current tolerances, resonant effects and load torque variations. Trinamics impressive driver technology is great but won’t change the laws of physics. I recommend looking hard at low cost closed loop stepper-based motor/driver units from Chinese firms like Leadshine. They blur the distinctions between brushless servo and stepper technology very nicely, offering ‘real’ x64 microstepping capability out of 100 pole motor construction and smooth loop closure with step/dir interface.
On the motion controller side, dont neglect the most recent Duet 3D print boards being introduced. These are provoking interest in the professional CNC world due to the safety engineering, embedded RTOS, and open source code base, and work well with a RPi front end.
Another consideration is the emulation of common mounts. There is a huge installed base of Skywatcher/Orion amateur mounts globally, for example, but only one TCS project (EQDrive out of Ukraine) I’ve seen that exploits that ecosystem by adopting the SW mount controller command set (perhaps with extensions). By adopting a de facto standard like this, your users benefit from existing investments they’ve made in Skywatcher mounts and accessories. I’ve also found Skywatchrt Engineering to be professional and accommodating of people who can customise or extend their platforms.
I hope my remarks don’t discourage you Andy. My experience over two decades has been that Astro engineering helped transform my professional engineering career from a stepping stone to boring old programme management and power politics to a far more satisfying one in technology consulting. I hope you are seeing that too!
Tony Owens
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The whole area of heat flows in gas expansion is messy Vlad. First decide whether you want a practical engineering approach to refrigeration-in-a-box or a romp around the relevant thermodynamics. In my practice, the latter follows the former, not the reverse.
Joule-Thompson cooling does not work with near-ideal gas mixtures except in close proximity to the discharging jet - where significant but very localised chilling is obtained. There are lots of other similar options to look at, one of which is the Rank-Hilsch vortex tube. They are actually used occasionally in controls enclosure cooling. Use of a low cost phase changing material e.g. propane/butane mix (AP30 aerosol propellant) is another possibility. But the cooling power of a discharging liquid AP30 jet which flashes from liquid to vapour during passage through a nozzle from 3 bar gauge to ambient is not a lot. And bloody dangerous if there are ignition sources around. There is steam jet refrigeration, possible using water/steam as a refrigerant too, and employing a steam-jet ejector to create near vacuum pressure to evaporate and chill a mass of liquid water. Lots of possibilities. But compressed air, in itself, isnt a good place to start when trying to create useful cooling within a fridge-sized enclosure!
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I think your design and design approach are fantastic Chris!
Like you I had to change my whole thinking about pathways to structural stiffness as a result of commissioning 'cheap plastic' prototypes in SLS or FDM from service bureaus. The apparent stiffness and damping with the parts perplexed me until I discovered the routine use of low density infill to cut material use. Hey presto, cellular lightweight plastic 'castings', with resonant frequencies comparable to homogenous metal parts!. My emerging practice now is to use like you a mixture of materials and processes in which FDM and SLS fit. Where ultra-stable 'mechanical grounding' of parts in the face of temperature humudty and load variations is required (as in some optics and some grinding operations) I specify waterjetted granite or moulded polymer concrete. For thermal stability but lower stability requirements I use steel or Permali Wood. For general structures and parts without any special strength or stability aluminium in all its forms was what I used.There has been a developing problem over the last 25 years with the gradual disappearance of jobbing machine shops in Anglo countries, presumably linked to the financialisation of their economies and a wholesale shift to Asian sourcing for consumer goods. This has made both my professional and 'hobby' work more difficult. I have responded by investing in basic machining and printing capability. I'm seeing a gradual substitution of SLS and FDM printed parts, with critical surfaces machined if necessary. I also source gravity and pressure die casting parts from India and mouldings from many sources including Poland and Spain, where previously I would have turned to UK and German firms.
The main reason I posted details of my 14" planetary Newt concept (I havent had time to start building one!) was to offer you a quantitative datapoint about gravitational sags and frequencies in a similar truss-type telescope structure for high resolution use. My concept used machined and extruded aluminium for most of the structure. I am not judging your structural concept about which I know little. FWIW given the cellular parts and super-light weight at the secondary end, I would be surprised if you were troubled by structural issues.
There are some unique advantages that apply to 3D printed parts for telescopes too. One of those, is high levels of insulation. For things that are within or close to the optical beamline, where metal parts like tubes and spiders if made of metal tend to sub-cool during clear nights, there is far less of an issue if cellular dimensionally-stable resins are used. Another is relative freedom from the need for coatings and finishes. Finally there is the ease of incorpating things like brackets, reinforcements, pneumatics and wiring. As you say, our profession is having to reinvent again all the established design techniques, in a world where the West now struggles to manufacture things profitably and where additive technology is finally becoming reliable and good enough for first-class products.
I'd be very interested in your progress on the Gregorian once the secondary is polished!
Good luck with your endeavours!Tony Owens
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Hi Chris and my compliments on your unorthodox monorail Gregorian. This style of 'monorail' tubeless scope reminds me of the late Horace Dall's planetary Dall-Kirkham.
I had a crack at designing a 14" F4 planetary prime focus Newt a couple of years ago. At the prime focus I could interchange various coma correctors, cameras and filters. I used ITEM alloy extrusions with screwed and epoxy-bonded joints and waterjet-cut pieces of 4mm and 10mm alloy plate to construct a goniometric primary mirror mount and various reinforcements to get the gravitational sag under control.
For a Newt the max tolerable decentration of the 'true' axis of the primary mirror from the eyepiece or camera to maintain no more than a 0.20 drop in Strehl is given approx by DeC = 0.005 . FR^3 [mm]. For my optic I therefore needed to assure no more than around 0.32 mm decentration of the primary from the camera, for all possible poses of the OTA and for the heaviest imaging train payload at the prime focus. This number is somewhat simplistic and debatable and little more than a guideline for acceptable structural sags, but as a target it was fine. In designing a structure I actually worked to around 25% of this target and aimed for a lowest natural frequency of around 20Hz. The thinking here was that the EQ8 mount I was planning to mount this on is marginally capable of supporting a 20Kg payload/counterweight combination with a natural frequency of around this. The natural frequency not just of the mount but of the entire scope/camera system needs to be as high as possible to allow a good percentage of quality frames when lucky imaging Moon and Jupiter at 120 Hz especially with some wind.
Here is what I ended up with:
I used a CFRP flat plate secondary single-stalk design which is magnetically fixed to the OTA using a kinematic mount for interchangeability. The mirror is contained in a lightweight shroud.
The structural deflections due to gravity (linear and tilt displacements) of the OTA at zenith pointing looked good.
This was Horizon Pointing showing less than 100um of linear sag of the prime focus group:
This was Zenith Pointing. Note how tilts of Primary and primae focus group matched:
This was another Horizon Pointing scenario with the OTA rolled through 90 degrees w.r.t. the gravitation direction. It proved to be the worst case but still the linear sags fell not too far outside my target:
This pic shows the lowest natural frequency of the OTA assuming a rigid circular saddle support of diameter 160mm is used. I call this 'Nodding Duck'. The frequency is 34 Hz which is perfectly acceptable:
This is the second lowest vibration mode, at 38 Hz. I call this 'Secondary Stalk Waggle':
Finally, this is the third lowest vibration mode which I named 'Primary Waggle'. It appears at 42 Hz so is not a concern:
My experience was that structural FEA was of tremendous help in arriving at something that almost met my stiffness requriements under all possible poses and imaging payload configurations. It never occurred to me to 3D print structural parts in something like PET-G using lightweight cellular infill at that time because to be honest I did not take FDM printing seriously. I since revised that silly opinion and am now gradually learning the practice of large 3D printing with a large printer. I am very encouraged to see your project and hope your practical findings about collimation stability show my own analysis to be too conservative!
best
Tony Owens
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What I'm looking for doesnt exist yet! I want a mount that has no meridian flips, no worm gears (despite all my work on refining EQ8's) no microstepped stepper motors, has a weight and size low enough to be airline cabin baggage, maintenance-free, cable-free, backlash-free, counterweight-free, capable of being rained-on without ill effects, and with at least a 20 Kg imaging payload. Perhaps combine the wireless servo controls and GUI of the AZGTi, provide differential timing belt transmissions, reinforced phenolic casework, wire race bearings and a single arm fork design... Or maybe something with delta 3d printer kinematics plus a 4th axis for image derotation?
One of the best resolved commercial designs I've seen recently is the Panther line of Goto mounts. Despite the counterweights!
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A good gloss of that period of hope and belief in the power of technology to effect change for the better. Spoiled a bit by the creaky voice (vocal fry) now fashionable among yuppie American women.
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All worm gear mounts of this class are pretty similar and better than 5 arcsecs peak-to-peak periodic error is typical. It doesn't make any real difference what the exact figure is, provided sensibly tuned autoguiding is being used. All will be reduced to 0.5" RMS on RA and a bit less on Dec, provided backlash is controlled. The EC mounts are a different animal, and essentially offer more linear RA or RA/Dec motion. But this is not a useful advance on open-loop tracking (no encoder/s) unless unguided imaging is a requirement and some mount modelling can be considered.
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It doesn't really matter which of the three you mention you choose, if performance is your major requirement. All are good solid mounts, all autoguide well. The 2015-on EQ8's/HD110's are better than the early mounts due to lower Dec backlash. The CEM ad AP mounts have spring loaded gears unlike the EQ8 which helps worm gear mesh clearance (i.e. backlash) control between summer and winter temperatures.
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3 hours ago, wimvb said:
Welcome to the wonderful world of kstars, Gina. I've been running my setup this way for more than a year now, and had no real problems this past season. As a matter of fact, when a friend's laptop broke down, we switched to an old RPi I had lying around, and were up and running in no time.
As you probably are aware of, I use Rock64 sbc's which has usb3, more memory (1, 2 or 4 GB), and supports both eMMC and larger SD cards than the Pi3. A larger SD comes in handy if you need to download astrometry index files and store your images locally during capture.
If you update your system to the latest stable versions of INDI and ekos/kstars, you'll find that offline astrometry is fully integrated. You only have to install the appropriate index files. This is a simple matter of clicking the files in kstars.
Btw, I'd recommend you test kstars on the Pi, and not on Mac/Windows. Just use RDP to connect to the Pi. Install xrdp on the Pi, and use Microsoft rdp on windows or Mac.
Good luck
Wim i'm interested in your Linux setup due to the USB3. In principle I should be developing my high resolution planetary imaging, but keep getting distracted onto other pursuits! What had stumped me in putting together a good fast planetary imager was the 2-3 metre length limitation of a ZWO planetary cams like the ASI174, when running flat out. The best resolution appeared to be a USB3-capable SBC mounted on the OTA or mount saddle plate, then off via hard Ethernet or WiFi to a server. But Intel NUC's are a bit pricey and delicate for that sort of outdoor exposure. Something else was required...
My understanding of USB3 on SBC's around 1 year ago was that basically very few exist and none are reliable. What has been your experience?
cheers
Tony Owens
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Sounds good Gina. That will get the scope back running by the shortest route.
Best Tony
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3 minutes ago, Gina said:
I'm having a problem understanding this. The screws I can't undo are the ones holding the lens cell in the tube. The ones holding the ring in the cell came undone easily.
OK. I was talking about how to remove and refurbish the entire cell complete with optics as a unit. Can you mark and extract the optics from the cell/tube assembly and get them out of harms way? If so, provided you photograph and carefully replace any lateral and axial shims used to centre the corrector, you could of course just decide to leave the cell alone. It would not be my choice (I dont take any nonsense from mechanical assemblies) but you could do that, and just clean the optical elements and replace them in the cell.
Otherwise, with the optics out, you can warm and extract the frozen screws as I've described. How many of these radial screws are being obstinate? Do you reckon they've been threadlocked in place? If so, the usual method of removing fasteners bonded with acrylic glues is to carefully heat the joint to 200C which softens the glue enough to break out the screw. A flame cannot be used due to the tube paint. But a soldering iron on the screw head might do the trick...
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2 minutes ago, Stub Mandrel said:
Phew, only just seen this thread - like reading a thriller! Let's hope the wonder fluid is suitably wondrous!
Accpording to teh web it's called 'Optical Wonder'
The MSDS says:
"2. COMPOSITION/INFORMATION ON INGREDIENTS
Chemical nature : (Preparation)
Description : Solution of the following substances with harmless additives.
Components CAS-No. EC-No. Symbol R phrase(s)
Concentration
Ethanol 64-17-5 200-578-6 F R11 25%
Propan-1-ol 71-23-8 200-746-9 F, Xi R11, R41, R67 35%
For the full text of the R phrases mentioned in this Section, see Section 16."Presumably the harmless additives are a tiny amount of surfactant?
Not sure. But washing broadband multicoated lenses is not rocket science and is low risk. There are not many moisture sensitive glasses used in astro correctors and eyepieces that are not BBAR coated and therefore quite cleaning-resistant. You need both organic and inorganic solvents to wash the lens then lots of DI water to flush. Mechanical cleaning by wiping with soft wetted tissue is a good idea provided scratching is minimised. Do the work in a plastic bowl and warm the diluent water. Whatever about high priced wonder fluid, there is nothing wrong with good old screen wash concentrate, diluted down with clean water. This contains alcohol/s plus a little acetone, in an aqueous base. Plus cool looking blue dye. Very important to flush several times with DI water. Car accessory shops will have this too! Dry by arranging in a rack (dishwasher drawer?) and gently using clean compressed air to blow off the drops. Not rocket science...
Tony
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Gina I have a couple of Intes-Micro Mak-Newts so I've experienced your issues. If you have time to do the job properly I'd follow Peter's advice and remove the cell and service the corrector and secondary properly. Marking the joints between every part with a small permanent Sharpie pen beforehand. Change the fasteners for stainless ones and either use silicone grease on the threads or seal them with a low strength loctite retainer. RS and Farnell have this. Warm the cell laid flat on a sheet of clean tissue in your domestic fan oven to 60 degrees, then remove and use good quality hex wrenches on the screws and they should release. If you manage to ream the head of one, carefully drill the head off using a Dremel and remove it that way. There are various ways to extract the remains, once the precious corrector and folding mirror are out of the picture.
Cleaned, reassembled and collimated it should be as good as new or better. If not, we have a high resolution Shack Hartmann analyser and a certified 1/10th wave autocollimation flat big enough, over here. I'd be happy to sort out any alignment problems you encounter FOC.
Tony Owens
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This is a different animal than a 'hypertune' or even an aftermarket worm. There are fundamental problems with the design of clutches and choice of worm and shaft bearings in the EQ8 which were addressed to some extent by the manufacturer after a mixed reception to the original product. I was one of the victims in fact...
The eventual result of my efforts was a new form of antibacklash worm gearing that also includes constrained layer damping to lower the meshing noise 'floor'. Also a redesigned clutch that can be tightened without imposing radial load on the shaft and inducing backlash and an image shift. Improved environmental sealing and a precision transfer timing belt drive to RA and many other improvements are there too. In combination with some other changes it amounts to a modernisation not an overhaul. A UK patent application on the gearing was filed at the end of 2018.
The effect is that there is no significant backlash on either axis, regardless of axis position, ambient temperature or wear. Nothing to fiddle with - the mount 'just works', as it should have done back in 2014 when I bought mine!
Tony
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3 minutes ago, StarDodger said:
Have you got any pictures of the mounts after the mod.. ? I would like to see how it looks..
and what exactly does the mod involve.. to eliminate the issues that comes with these mounts...
i Just got hold of a secondhand d EQ8 for a very very good price, under £1200 and it’s mint (well after swapping all the bolts for stainless steel ones anyway) and one of the later ones it’s 3 years old..
There will be a website at some point but finding time is an issue for me.
There is a special interest Yahoo Group about EQ8's here that includes various contributions from me about the project here: https://groups.yahoo.com/neo/groups/SkywatcherEQ8/info
Pictures of the mount and our shipping crate for couriered collection and return:
Picture of before and after polar plots (5 test points, equally-spaced around each axis) showing the effect of the new gearing on backlash as benchtested:
Dec Backlash as tested on the sky with PHD2 and a 1180mm EFL 20 Kg autoguiding payload:
The autoguiding performance has been tested and shows around 4" pk-pk periodic error for the new RA gearing, which corrects down to 0.40" RMS on RA and 0.35" RMS on Dec with careful tuning of settings on PHD2. There is some work still ongoing on improved autoguiding involving different motor firmware and a new ASCOM server which offers certain advantages over EQMOD in principle, and perhaps also in practice. We shall have to see!
Tony Owens
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Welcome David!
Tony
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I'm late coming to this discussion - apologies. One potentially interesting avenue to consider, against the CEM120 and upcoming centre-mount competitor model from Skywatcher, is an upgraded EQ8. I need to disclose that I make these so have a vested interest. But ignoring that for a minute. Some of my spare time over the last few years has gone into sorting out the limitations of this mount and this has been quite successful. Imaging load capacity, and guiding responsiveness and accuracy are significantly improved due to use of stiffer ground steel shafts in place of the aluminium originals combined with different worm bearings, damped, diamond-lapped antibacklash gears and now a new ASCOM server named Green Swamp, specifically designed for this mount. Through-the mount cabling is relatively trivial to implement if needed as the axes are hollow. Custom saddle plates for larger instruments and cranked piers for eliminating meridian flips are straightforward too.
This route makes sense for those more interested in functionality than 'bling'. Specifically, for people who:
1. already own early EQ8's with large Dec backlash issues which make good imaging difficult
2. need a reliable, economical, heavy imaging mount/s for remote use, and are unconvinced of the superiority or practicality of unguided encoder mounts
3. are willing to consider buying a cheap used EQ8 as a basis for upgrade
The cost of our modernisation runs 1200-2000 euros plus VAT where applicable, depending on spec.
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12 hours ago, cotak said:
I for one am glad there's little nationalistic politics here. I found that stuff on the other forum unpalatable.
It is a good thing that more manufacturers are at a state where quality can be produced at reasonable price. IMHO the quality gap was always more about perception than performance...
The Skywatcher brand is about cost leadership not innovation. But the engineering is pretty solid. They aren’t the most popular brand for nothing.
That said there is plenty of scope to improve many of their products and performance improvements are sometimes embarrassingly easy to effect.
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You're a brave chap Gordon.
I'm most impressed at your project planning - critical people like neighbours and planners squared off in advance!I think your farmer neighbour's kids ad their friends will need to be shown the sights when the scopes and cameras are installed and the warm room running. That was a dodgy-looking tractor and I can imagine stress levels were high during those lifts!
Bravo!
Tony Owens
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12 minutes ago, Gina said:
Just tried to separate the casing parts at the flange and it's stuck solid most of the way round. So much so that the casing has broken trying to prise it apart!! OTOH the seal for the USB cable, also apparently well sealed with lots of sealant is leaking profusely. Looks like I need to change the design completely.
Have you a lathe Gina?
If so you could consider printing the mating flange surfaces with loads of skin thickness and then face the flanges and machine a 2mm deep x 3.2mm wide O-ring groove into one, for a BS1806 2.62mm cord dia O-ring in whatever ID you need.
Bit too lush maybe?Tony
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Is that transparent dome polycarbonate or PMMA or glass Gina?
And are you binning the images?
EQ8 DEC backlash question..
in Discussions - Mounts
Posted
I'm sure Bog Snorkelling is an important formative experience for Irish undergraduates:
As for Green Swamp server (GSS) its been around for a while. Unlike EQMOD its in active development. Initially the target mount was just EQ8/HDI 110 but it now includes other Nantong Schmidt EQ mounts.
There are several controls which extract better performance from EQ8's when autoguiding than EQMOD does. One, is homing that is far more reliable. But the key ones for imagers are motor current doubling during tracking and autoguiding, (which doubles stepper motor torque in small corrective moves to reduce following error) and use of short range GoTo commands while autoguiding using pulse guiding. These improve corrective move accuracy, reducing control loop dither around the target position. It is necessary to download a bugfix version for the EQ8 firmware to access the full feature set. There is a discussion groups here: groups.io/GSS/
Tony