With an Amazon Fire Tablet, on which I placed SkySafari Pro ($15), we can now get the OnStep mount at Hopewell Observatory to go to any target we want, without any wire connection needed at all. The ‘Smart’ Hand Controller is no longer a necessity, which is good, because it’s always been rather a PITA.
The SkySafari Pro interface is really nice and much more user-friendly than any other planetarium software I’ve tried so far. Among other things, you can use your fingers to pan around and zoom into the sky map display, and double tap on a target of interest. Once you’ve located your target on your screen, you can then press ‘GoTo’, and the scope will begin slewing to that target. While it’s doing so, you can watch where the telescope is currently pointing to on the screen’s display, kind of like those airplane icons on maps on some airline flights – only a lot more accurate and zoomable. BTW the connection is via WiFi.
Once the scope thinks it has arrived at the proper location, you can look through the eyepiece (or at a display screen) to see if it is properly centered. If not, then in order to center it, you simply tilt the tablet in the direction you want the scope to go! And changing the speed of such movement is really easy!
I have thanked Arlen for showing me this on his cell phone. I myself could never get it to work properly with my iphone, but after some time downloading the proper software onto the tablet and making the proper wifi connections with the proper IP address and port number, in a nice warm location here in town with at least a halfway decent WiFi connection, with a spare OnStep setup on the bench in front of me, then it was easy.
I demonstrate this with the following clumsy video.
BTW, SkySafari Pro works on Android and other tablets, on MacOS, Windows, and supposedly even on iPhones. You do need to pay for the Pro version, because the free version does not have telescope control capabilities.
So, for very little money, but a whole lot of work, we have 21st-century Wi-Fi control over a very fine telescope mount!
For the first time since Fall of 2019, the Hopewell Observatory is holding a free, public, night-time open house so you and your friends and family can get good looks at Saturn, Jupiter, the Moon, star clusters, galaxies, and nebulae, through our telescopes, and with your own eyes, rather than via photographs.
The date is Saturday, October 15, 2022, with a rain date of October 22. We suggest arriving near sundown, which will occur at about 6:30 on the 15th, and about 6:20 on the 22nd.
It’s about 45 minutes by car from where I-66 intersects I-495 by car. The last two miles of road are dirt and gravel, and you will need to walk about 300 yards from where you park. We do have electricity, and a heated cabin, but since we have no running water, we have an outhouse and hand sanitizer instead.
We are located about 30 miles west of the Beltway on Bull Run Mountain – a ridge that overlooks Haymarket VA from an elevation of 1100 feet, near the intersection of I-66 and US-15. Detailed directions are below.
Assuming good weather, you’ll also get to see the Milky Way itself, although not as well as in years past, because of ever-increasing light pollution.
If you like, you can bring a picnic dinner and a blanket or folding chairs, and/or your own telescope, if you own one and feel like carrying it. We have outside 120VAC power, if you need it for your telescope drive, but you will need your own extension cord and plug strip. If you want to camp out or otherwise stay until dawn, feel free!
If it gets cold, our Operations Building, about 40 meters north of the Observatory itself, is heated, and we will have the makings for tea, cocoa, and coffee.
Warning: While we do have bottled drinking water and electricity and we do have hand sanitizer, we do not have running water; and, our “toilet” is an outhouse of the composting variety. At this time of year, there are almost no insects of any kind, although it’s always wise to be safe and check yourself for ticks after you get home.
The road up here is partly paved, and partly gravel or dirt. It’s suitable for any car except those with really low clearance, so leave your fancy sports car (if any) at home. Consider car-pooling, because we don’t have huge parking lots. We will have signs up at various places along the way to help guide you, and will try to have parking spaces denoted.
Two of our telescope mounts are permanently installed in the observatory under a roll-off roof. We have others that we roll out onto the grass in our roughly one-seventh-acre field. We have two 14-inch scopes (one hand-made Dob and one Celestron SCT), and a 10” f/9 reflecting scope also made by hand. We are about to install a brand-new Astro-Physics GoTo computerized mount in addition to our sturdy, highly accurate, but 1970s Ealing mount. The entire observatory was hand-built, and is largely maintained, by the labor of its founders and current members. We also recently re-built the electronics and motors for the Ealing mount using stepper motors and an open-source system called OnStep.
The drive is about an hour from DC. After parking at a cell-phone tower installation, you will need to hike south about 300 yards to our observatory. Physically handicapped people, and any telescopes, can be dropped off at the observatory itself, and then the vehicle will need to go back to park near that tower. To look through some of the various telescopes you will need to climb some stairs or ladders, so keep that in mind when making your plans.
It’s not the inky-scary dark of the Chilean Atacama or the Rockies, but Hopewell Observatory is mostly surrounded by nature preserves maintained by the Bull Run Mountain Conservancy and other such agencies. Also, our Prince William and Fauquier neighbors and officials have done a pretty good job of insisting on smart lighting in the new developments around Haymarket and Gainesville, which benefits everybody. So, while there is a pretty bright eastern horizon because of DC and its VA suburbs, we can still see the Milky Way whenever it’s clear and moonless.
The easiest planets to find will be Jupiter and Saturn. Jupiter’s stripes, bands, and four large moons will be spectacular, as will be Saturn’s rings. We should also be able to view Mars, Uranus and Neptune, as well as many deep-sky objects such as galaxies, star clusters, and nebulae.
You can find detailed directions and a map to the observatory below:
DIRECTIONS TO HOPEWELL OBSERVATORY:
[Note: if you have a GPS navigation app, then you can simply ask it to take you to 3804 Bull Run Mountain Road, The Plains, VA. That will get you very close to step 6, below.]
(1) From the Beltway, take I-66 west about 25 miles to US 15 (Exit 40) at Haymarket. At the light at the end of the ramp, turn left/south onto US 15. (Exit is at approximately latitude 38°49’00″N, longitude 77°38’15″W.)
(2) Go 0.25 mi; at the second light turn right/west onto VA Rt. 55. There is a Sheetz gas station & convenience store at this intersection, along with a CVS, a McDonald’s, a Food Lion, and a Walmart-anchored shopping center on the NW corner that includes a number of fast- and slow-food restaurants, including a Starbucks.. This is a good place to stop for restrooms or supplies.
(3) After 0.7 mi on Va 55, turn right (north) onto Antioch Rd., Rt. 681. You will pass entrances for Boy Scouts’ Camp Snyder and the Winery at La Grange. (38°49’12″N, 77°39’29″W)
(4) Follow Antioch Rd. to its end (3.2 mi), then turn left (west) onto Waterfall Rd. (Rt. 601), which will become Hopewell Rd. (38°51’32″N, 77°41’10″W)
(5) After 1.0 mi, bear right onto Bull Run Mountain Rd., Rt. 629. This will be the third road on the right, after Mountain Rd. and Donna Marie Ct. (38°52’00″N, 77°42’08″W) Please note that Google Earth and Google Maps show a non-existent road, actually a power line, in between Donna Marie Ct. and Bull Run Mtn. Rd.
(6) In 0.9 mi, enter the driveway on the right, with the orange pipe gate. There is a locked stone and metal gate on the left, opposite our entrance, labeled 3804 Bull Run Mountain Road. Don’t take that road – it goes to an FAA radar dome. Instead, go to the right (east). We’ll have some signs up. This is a very sharp right hand turn. (38°52’36″N, 77°41’55″W)
(7) Follow the narrow paved road up the ridge to the cell phone tower station. You should park around the tower (any side is fine) or in the grassy area before the wooden sawhorse barrier. Then you should walk the remaining hundred meters to the observatory on foot. Be sure NOT to block the right-of-way for automobiles.
(8) If you are dropping off a scope or a handicapped person, move the wooden barrier out of the way temporarily, and drive along the grassy track to the right of the station, into the woods, continuing south, through (or around) a white metal bar gate. The few parking places among the trees near our operations cabin, the small house-like structure in the woods, are reserved for Observatory members. If you are dropping off a handicapped person or a telescope, please do so and then drive your car back and park near the cell phone tower.
Please watch out for pedestrians, especially children! The observatory itself is in the clearing a short distance ahead. We do not have streetlights, and there will not be any Moon to light your way, so a flashlight is a good idea. In the operations cabin we have a supply of red translucent plastic film and tape and rubber bands so that you can filter out everything but red wavelengths on your flashlight. This will help preserve everybody’s night vision. In the cabin we also have a visitor sign-in book; a supply of hot water; the makings of hot cocoa, tea, and instant coffee; hand sanitizer; as well as paper towels, plastic cups and spoons.
The location of the observatory is approximately latitude 38°52’12″N, longitude 77°41’54″W. The drive takes about 45 minutes from the Beltway. A map to the site follows. If you get lost, you can call me on my cell phone at 202 dash 262 dash 4274.
At long last, we have finally got the venerable, massive Ealing telescope mount at Hopewell Observatory working again, after nearly 9 months, with a totally different, modern, electronic stepper motor drive based on Arduino.
My first post to the OnStep group ( https://onstep.groups.io/g/main/message/37699 ) was on October 21, 2021, over eight months ago. In it, I wrote that I had decided to give up trying to fix the electro-mechanical synchronous drive and clutches on our Ealing-Byers mount at Hopewell Observatory, and asked the folks on the OnStep message boards for help in choosing the best OnStep combination to drive such a mount.
Since then, it’s been a very long and steep learning curve. We only fried a couple of little slip-stick drivers and maybe one MaxESP board. We got LOTS of help from the OnStep list (not that the posters all agreed with each other on everything)! We ran into a lot of mysteries, especially when we found, repeatedly, that configurations that worked just fine on our workbench wouldn’t work at all when the components were put into the mount!
But now it works.
Let me thank again in particular:
* Prasad Agrahar for giving me the OnStep idea in the first place by showing me a conversion he had done;
* Alan Tarica, a fellow ATMer, for cheerfully partnering and persevering with me in working on this project for the past 8 months in many, many ways;
* Ken Hunter for providing tons of basic and advanced advice and a lot of hardware, all for free;
* Robert Benward for extremely helpful advice and drawings;
* George Cushing for providing some of the original boards we used;
* Khalid Bahayeldin for lots and lots of OnStep design features;
* Howard Dutton for designing, implementing, and supporting this whole project in the first place; and
* Arlen Raasch for bringing his wealth of trouble-shooting experience and a lot of nice equipment up to Hopewell, spending full days up there, and saving our asses in figuring out the final mysteries. Among other things, he kluged (by the way, “kluge” is German for “clever”, not clumsy) a level shifter to make it so that the 3.3 volt signals from our MaxESP3 board would actually and reliably communicate with the higher-voltage external DM542T stepper drivers that controlled the very-high-torque NEMA23 steppers, rewiring some of the jumpers on our already-modified MaxESP boards, and making the wiring look professional, and other stuff as well, thus essentially pushing us over the finish line.
* All of the Hopewell members for supporting this project
* Bill Rohrer and Michael Chesnes who physically helped out with soldering and wiring work at the observatory.
I plan to write up a coherent narrative with a list of lessons learned, and perhaps I can help make some of the step-by-step directions in the OnStep wiki a bit clearer to the uninitiated. Obviously I’ll need to write a user guide for this mount for the other Hopewell members.
If Alan and I had gone straight to our final configuration, this project would have been quite a bit cheaper. In addition to what’s inside the mount and control box at the observatory, we now have on hand something like this list of surplus items:
* four MaxESP boards in various stages of construction and functionality;
* a dozen or more different slip stick stepper drivers we aren’t using;
* four or more external stepper drivers, mostly TB6600;
* five or more stepper motors of different sizes;
* a hand-held digital oscilloscope;
* lots and lots of wires of many types;
* lots of metal and plastic project boxes of various sizes;
* lots of tiny motherboards; and
* lots and lots of sets of various mechanical electrical connectors (many were used, later cut off, and then ended up in the trash).
Yes, one does need spares, and yes, lots of this stuff has multiple uses, but this has not been a ‘green’ project. On the third hand, it has been extremely interesting and fun to learn all these new skills.
The final substantive changes that got the Ealing mount up and running were made during the Fourth of July fireworks down in the valleys on each side of the ridge that our observatory sits on. What were the changes? (1) switching the black and white leads from the mains power leads (they original, scavenged, cord had the white lead as Hot!) and (2) reversing the Declination motor direction. It also helped that I was not zoned-out and punchy from lack of sleep, as we had been when Arlen and I had last worked on it.
On July 4th, it at long last worked properly!
This Ealing mount’s original, labeled, built-in manual RA and DEC setting circles make it quite easy to put the scope into Home position before you turn on the power. One just loosens the clutches and moves the axes to 6:00 hours exactly in Right Ascension and 90 degrees exactly in Declination. From there, I found the OnStep system behaves very nicely. It accurately slewed to a number of bright, obvious targets of various sorts on both sides of the meridian. However, when I tried to get it to aim that night at M13, it refused, sending an error message that it was too close to the zenith for safety. And it was (altitude 87 degrees)! Very impressive – a safety feature I hadn’t even known about!
None of the objects that I slewed to was far from the center of the field of view, even when the scope slewed across the meridian. I was using an old, 2-inch diameter 50 mm Kellner eyepiece on an f/12 six-inch aperture D&G refractor.
I found that the Android app to be **much** better for initial setup than the SHC. Arlen, Alan and I all found that setting the correct latitude, longitude, UTC offset and so on from the SHC was a real brain-twister because of its unfortunately not-very-friendly user interface. Using the OnStep app on a cheap, old Android tablet made the whole initialization process very much easier and faster, especially after I let the tablet discover what time it really was from my iPhone’s wireless HotSpot.
However, I found that the hand paddle is much better for fine-tuning of pointing and so on, because the bright display on an Android, no matter how dim one makes it, will destroy one’s night vision, and one cannot reliably feel where the directional buttons are on a flat screen while staring through an eyepiece. Obviously, one can feel the buttons on the SHC quite well, maybe even with gloves. A joy stick would be even better…
Alan and I and the other Hopewell members still have many more OnStep features to learn.
However: if I had known this project would take over eight months of hard work, I think I might have tried fiddling with the original Ealing clutches some more.
Oh well, we have a mount that has much more capabilities than it ever had, and Alan and I have learned quite a bit of electronics! I’m proud of what we did!
For many months, we members of The Hopewell Observatory have been doing our best to repair the 50 year-old clock drive on our university-grade Ealing telescope mount.
Yesterday, after a lot of help from others, I finally got it to work — at least in the day time. With no telescopes mounted on it. And 100% cloud cover. So I really don’t know for sure.
We still need to test it out on a clear night, to see how well it tracks and finds targets.
I think I will re-configure the wiring so that it fits in a box outside the mount, instead of using the weirdly-shaped compartments inside: one needs to do occasional maintenance on the OnStep hardware and software, and none of that is easy to access right now.
I think I have figured out what was going wrong with our OnStep build:
Our unmodified Arduino-based, green, MaxESP3.03 OnStep micro-controller unit board had two major errors: it didn’t put out any signal at all in the Enable channel in either Right Ascension or in Declination, and in Declination, the Step channel didn’t work either. (I can only guess what caused this, or when it happened, but these errors explain why we couldn’t get this particular board to work any more.)
We had the connecting wires between the two blue, modified boards of the same type and the external TB6600 stepper drivers in the wrong arrangement. We stumbled upon a better arrangement that Bob Benward had suggested, and indeed it worked!
I never would have figured this out without the nice hand-held digital oscilloscope belonging to Alan Tarica; his help and comittment to this project; advice from Ken Hunter that it was a bad idea to have the boards and stepper drivers connected, because the impedance of the motors makes the signal from the board too complicated, and also the signals to the motors themselves are extremely complex! Let me also thank Bob Benward for making beautiful and elegant schematics from the drawings I’m making with pencil and eraser on a couple of 11″x17″ sheets of stiff art paper and pointing out the anomalies between our (Ken’s? I thought I was faithfully copying his arrangements….) original wiring connections and what the manual recommends.
I’m puzzled that our earlier arrangement worked at all. Given that this oscilloscope sees extremely complex, though faint, voltage curves from my own body (anywhere!), I am guessing that electrical interference fooled the drivers into sending the correct commands to the stepper motors even though the STEP and the DIRECTION wires were crossed.
In any case, I attach tables summarizing what I found with the same oscilloscope I had in the previous post. I have highlighted parts that differ between the three boards. Boards “Oscar” and “Linda” are basically identical ones, both of them modified to bypass the location where small, internal stepper motor drivers (about the size of the last joint on your pinky finger) are normally held. Instead, these two boards, both blue in color, connect to two external black-and-green stepper drivers about the size of your hand.
Board “Nancy” differs from the other two in a number of ways: it’s green, which is not important for its function but makes it easier to distinguish. It is also an unmodified one, and it carries TMC5160 stepper driver chips pushed into two rails.
I used orange and green to highlight the differences in output.
With electronics: when it works, it’s amazing, but it is very, very fragile.
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Edit: It all works just fine on my desk. I hope it will also work once we put it into the telescope’s cavities and wire everything up!
We are still at work trying to debug our OnStep re-build of the venerable Ealing telescope drive system at Hopewell Observatory.
Without having a whole lot of experience with oscilloscopes, we used a brand-new OWON 200-series hand-held unit to measure the output of our various MaxESP3.03 boards towards the stepper motors. We don’t really understand what these waveforms actually mean, and a brief search of the OnStep wiki page does not immediately point me to screenshots of what the signals should look like under various conditions.
In any case, some of the waveforms we see look like simple square wave signals. Some look like weird semi-random combinations of square waves, and some look like just plain noise.
In this first video, we have an unmodified MaxESP3.03 board with TMC5160 drivers, not connected to any stepper motors. I attached the ground pin of the probe to one of the grounding grommets at a corner of the MaxESP board, and systematically probed the pins that come out towards the various windings on the stepper motor. We also pressed N, S, E, and W buttons to see what happened. Here goes:
Those of you who are experts on this: do these waveforms appear to be OK to you in this situation?
This next setup is different. It’s a MaxESP3.03 board that Ken Hunter has modified by adding or moving about ten jumpers on the underside of the board; it has no slip-stick drivers for RA or DEC mounted on the MaxESP board itself. Instead, each axis has three (not four) wires coming out of the same place that four wires generally come out to connect to your stepper motor; these three wires connect to four of the inputs on an external, and separately-powered TB6600 stepper driver, which then feeds four wires to the two coils on the stepper.
The arrangement we have now does seem to work, at least on our workbench at the ATM workshop in Chevy Chase Community Center in NW DC, as you can see and hear in this video, but, once again, neither Alan nor I have any idea if the waveforms are correct. Here is the video:
Again: experts — do you think those waveforms are correct?
We were surprised at how complex, and apparently noisy, are the signals on the Step and Dir lines from this modified MaxESP board to the green-and-black external TB6600 drivers. They don’t show up at all in these two previous videos, but they will show up in the next one, which I’m having a bit of trouble uploading at the moment.
In that video, I test both RA and DEC output.
In RA, pin #1 is Enable and is apparently not connected to anything. It produces a wave that looks like a crosscut saw seen from above that has teeth very widely spaced apart. That ENA signal doesn’t change no matter what buttons we push; we think the graph is merely showing interference from something or other.
Still in RA, pin #2 is the STEP pin, and it produces a nice square wave that changes dramatically in frequency when you press the E or W buttons on the SHC. We don’t really see the difference between the E or W graphs.
Still in RA, and in contrast, the graphs for both the Dir and GND pins seem to just look like noise. When one presses ‘E’ the noise graph from the Dir pin definitely changes voltage (it drops off the screen), but not when we press ‘W’. Nothing happens to the noise graph on the fourth pin (GND), no matter what we do.
On the DEC side, all pins seem to put out flat but noisy signals. The noise signal on Pin 2 (Step) moves dramatically but identically lower when you press either the North or South button on the SHC. The noise signal on Pin 3 (Dir) does not change when you press buttons, and neither does the noise signal on pin 4 (GND).
We are still trying to get our venerable, university-grade Ealing mount to work properly with its new OnStep motor drive system. We thought we had – at long last – everything set up perfectly and running correctly with the various components wired up properly but not yet pushed into place in the interior cavities of our mount. All seemed to be working well until we pushed the last components and wires inside, and then closed the hatches.
Then things stopped working.
We soon figured out that the force we had to use when moving all those items inside the mount had broken some of the leads. We found those broken leads and replaced them with shorter ones.
When we started it up again, we discovered that the mount would not ‘track’ to the west in right ascension — something that the software and hardware are programmed to do as soon as the system is turned on. In fact, I couldn’t slew it to the west either. Eastwards was no problem. Also, we could only slew southwards, not northwards.
We didn’t know what to do, so I emailed a followup question to the wonderful folks at the OnStep wiki. Several folks thought we had a balance issue or a limit switch issue, but I went up today to check on the balance — and concluded that’s not the problem. We have no limit switches yet either in hardware or in software. So that’s not it, either.
Wondering if we had somehow screwed up the MaxESP3 board that is the heart of the OnStep system, I unplugged the board (and all of its sub-boards, as a unit) we had been using last weekend, and plugged in a duplicate board, built by Ken Hunter and ‘flashed’ by him with the same Config.H file as the other one.
Listen to the screeching!
This weird behavior is not the same weird behavior we were getting with the other OnStep MaxESP3.03 board. What on earth is going on?
Another suggestion is that we may be creating ground loops by not connecting our wiring properly. I don’t know. I wish I had taken some electronics classes during my time in college. It would have come in handy here!
I’ve got the new stepper motors, and their drivers, and their power supplies, working away just fine on my desk, and I’m pretty excited and confident that we will have enough power and precision to drive and slew the Ealing properly!
Counter-clockwise from top: Plug strip; Android tablet; OnStep board in black box; 24VDC power supply; weather module; smart hand controller; NEMA23 steppers (2 of them) with connectors on top; two drivers for the steppers; another power supply.
These steppers are very strong: I am completely unable to stop the motors with my hands (bare or gloved) either when they are just tracking or when they are slewing at full speed or guiding at low speed, even with a fairly large fixture on the end of the shaft.
Without Ken Hunter’s expertise, there is no way I could have figured out how to get these particular steppers wired so that they would run, especially since they require those special, large, green and black drivers that you see in the photo above, which are about the size of the palm of your hand. Ken deserves a real round of applause, and more. (I have found that his advice on the OnStep wiki message board is much more accurate and friendlier than the advice of many others there.) In addition, he also repaired two boards that had been incorrectly soldered and assembled by someone else and which I and Alan Tarica purchased from that person, separately.
Before Ken’s intervention, the boards didn’t work. He found a number of assembly and soldering errors, and not only fixed them, but he also ‘flashed’ them with the latest OnStep software versions. At no cost! Now, they work very well.
I want to thank Prasad Agrahar again for his original inspiration and follow-through, and also Alan Tarica for his enthusiastic and knowledgeable assistance and advice (which I don’t always follow).
What’s more, as far as I can tell, this arrangement with super-duper steppers and drivers is unique in OnStep. Something like it clearly exists in some form in the professional or amateur CNC world, which is why we can purchase these insanely complex drivers for less than $9 apiece and the steppers for just $37 each, but to my knowledge nobody in the OnStep world has done this particular arrangement.
The old NEMA-23 steppers and these new ones have the exact same ‘form factor’ except that one can use larger bolts to fasten the new ones to the L-shaped brackets I already have installed.
The attached schematic diagram is a first draft of how the connections on the mount itself will be made. The wiring job is going to have a lot of parts, and lots of connections!
At the observatory, we won’t have those old military-grade, 14-connector cables any more, nor that very heavy old hand paddle whose cable we all used to trip over. Instead, I ordered 10 feet of 14-gauge, 4-conductor shielded, stranded cable that is highly rated for both high and low temperatures, in order to connect the DEC drive to the rest of the scope. It will need new strain-relief grommets. So will several other wires. I can re-use most of the existing holes in the cover plates for this mount, and will seal the rest of them to keep out insects. Wiring all of those new connections will take a while!
We will have a local wireless connection (with a small external antenna, like on a router, to make sure there is a good wireless signal), and a small (2x3x5 cm) dedicated basic weather monitor (very basic: just humidity, temp, etc) attached somewhere on the mount*. There will also be an emergency ‘Kill’ switch to allow one to stop the drive immediately if needed.
You can control the scope with a Smart Hand Controller that will be attached via a flexible ethernet-type cable, or, if you prefer, with an inexpensive Android cell phone or tablet that has the proper software installed. (We will leave a tablet up there, with its charging cord.) One won’t need to unclamp, slew, and re-clamp the RA and DEC axes any more in order to acquire a target. We will see how good the pointing accuracy and tracking are, once it’s all up and running.
Since we are using much stronger stepper motors than the ones had been suggested to me and that I had purchased earlier, and they needed a lot more current, we needed different drivers. As a result, most of the connections I had previously fabricated won’t be of much use for us anymore. Perhaps I can give them away to somebody else who is attempting an OnStep conversion on a telescope mount that weighs much less than this one.
Here is a little video of these things in action:
And here is my first draft of the schematics showing how these things all connect inside the scope as well as how we will connect them to the body of the mount itself. It’s crude, but I think it will be useful.
A 3-minute video of the results of our first-time installation of something called an OnStep conversion. We are replacing the telescope drive of a venerable but beautifully machined telescope mount, located at a small group-owned observatory called Hopewell, atop a ridge called Bull Run Mountain*.
It’s alive!
Sorry, it’s not the greatest or clearest video. Also, I mistakenly state at about 0:25 in the video that the right ascension axis was turning at 12 RPM, but it’s not: I should have said 5 RPM, or one revolution in 12 seconds.
You can hear some stuttering of one of the motors. You are right, that is not a good sound. We were able to get it to stop and start making that noise and motion by adjusting the precise positioning of some of the gears. It will take some time and experimentation to get that perfect.
Later on (not captured in this video), when I was trying to slew in the declination axis at the highest speed possible, the stepper motor once again screamed and halted. I’m hopeful that all of those problems can be fixed by doing one or more of these things:
1) adjusting the fit of all those gears;
(2) changing certain parameters of microstepping and current to the stepper motors in software; and/or
(3) increasing the voltage to the board from 18 VDC to 24 VDC.
I’ll need to test things out on my desk at home, using the same OnStep board, but without the gears and timing belt. (That stuff was a royal PITA to remove screw back into place, and none of us have any desire to take them back out again!) I have some identical extra stepper motors that I can test out, with gloved hands, to see if it is possible to stop the motors from turning. Right now, I still don’t think they are putting out the amount of torque needed.
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*Yes, that famous Bull Run of Civil War fame is not far away. However, our observatory is named after a different geological feature, namely the Hopewell Gap that cuts through the hard rock of Bull Run Mountain right about where where the creek called Little Bull Run begins.
If you are reading this, you probably know that serious amateur, and all professional, astronomical telescopes (except for Dobs) are generally driven by ‘clock drives’ so that the object one is viewing or photographing stays properly centered as the earth rotates imperceptibly beneath us. The original Ealing motor drive at Hopewell, while turning excellent Ed Byers gears, had been an intermittent problem ever since it was delivered to the University of Marylandabout 50 years ago. It was in fact not operational when they sold it to us for a pittance about 30 years ago. (If you go to the University of Maryland Observatory site I linked to, the scope we have now is the one in the center of the 1970s – era photo labeled ‘Figure 4’.)
Bob Bolster, one of the founding members of Hopewell observatory, disassembled the drive, modified it considerably, and got it working again, several years before I joined the group. The scope worked, off and on, with a very complex clutch system for ‘fast’ and ‘slow’ movement of the scope, for most of the rest of the last 25 or so years, except for occasional motor burnouts and clutch replacements. Also unfortunately, the optics on the original 12″ Ritchey-Chretien telescope, were not very good, so we removed them, had them in an attic for many years, re-tested them, and finally sold the glass and the holders, for a pittance, to someone in Italy who wanted to try to re-figure them.
This was originally a ‘push-to’ telescope, meaning that one loosened up two Byers clutches (one for each axis), located the desired target in the sky, tightened the two clutches, did some fine tuning with an electric hand paddle to center the target more precisely, and then allowed the telescope drive to then keep the object in the center of the eyepiece or camera field of view as long as one wanted. It originally came with metal setting circles (basically, finely-made protractors that showed where the scope is pointing vis-a-vis the polar and declination axes), which made finding targets possible, though not trivial!
About 15 years ago, Bolster (with some help from me) installed Digital Setting Circles, which used a rotary encoder on each axis, along with a small hand-held computer and screen display, to allow one to select a given target; the DSC hand paddle’s display then would indicate how far one should rotate the scope along those axes to find the desired celestial object; when it was in the field of your widest eyepiece, one used the hand paddle to center it more precisely.
Converting this scope to an OnStep drive will, I hope, make this a Go-To scope in which one can command the telescope to aim at whatever target one desires.
Unfortunately, right now, the fastest it seems to rotate in Declination, with no load whatsoever (all scopes have been removed, so no balance or inertia problems) is about one degree per second. So doing a 180-degree turn in a North-South direction would take a full three minutes. A 30-degree turn would take 30 seconds. Can we make this a bit faster? I hope so.
I wasn’t able to really slew in right ascension (East-West) because the counterweight box, even though empty, seems to require too much torque to rotate right now.
Bolster passed away a few years ago, and this summer, the moment I had been dreading finally arrived: the drive on the Ealing died again, and his amazing skills and tenacity in fixing such problems was gone with him. What’s more, in his final years, his incurable, chronic idiopathic neuropathy made it literally impossible for him to speak, and even typing email responses to the rest of us took a very long time. So most of his wealth of knowledge and experience died with him.
As indicated in my earlier posts (here, here, here, and here), with help from others, I was able to take the two motor setups for the two axes out from the mount and get them working again on my workbench in their original format. I was even able to order and install material for the clutches. However, I discovered that one needed to adjust the clutches very, very precisely, or else they wouldn’t work at all.
I couldn’t figure out how to do that.
And nobody else who belongs to our observatory volunteered to help out, except for removing the scopes and drives from their former positions inside the mount.
So I decided to convert to a totally different type of telescope drive, one inspired by the Arduino boards and 3-D printers. A group of really smart and resourceful hobbyists (engineers?) designed a system around the Arduino environment that uses inexpensive off-the-shelf printed circuits and complex sub-boards and components, used originally mostly in the 3-D printers that have become so popular, to drive at telescope just the way astronomers want them to be driven.
Apparently, there have been many, many OnStep successes, but what we are doing may be the largest and most massive mount to date that has done such a conversion.
I was warned that the entire process would take some months. Those warnings were correct. But that’s OK. I’m retired, I have time, and I have access to tools and people who are interested in helping. What’s more, I have learned a whole lot about modern electronics, and my soldering skills are much better than they ever were.
I’d again like to thank Alan Tarica (who’s physically helped a **tremendous** amount), Prasad Agrahar (who first showed me the OnStep conversions he had done on a much smaller equatorial mount), Howard Dutton (who first conceived and implemented OnStep), Ken Hunter (who made and **donated** to us a complete, functional OnStep board together with all sorts of accessories and walked me by phone and video through many of my fumbling first steps), Khalid Bahayeldin, George Cushing, and many others.
I have made a lot of progress over this winter break in converting the 50-year-old Ealing telescope mount at the Hopewell Observatory, as you can see in this video.
We are swapping out an electro-mechanical “dumb” drive that failed, in favor of a modern, solid-state one built in the Arduino environment. If it all works out as planned, this mount will be able to slew to any target and keep the target steady enough for astrophotograpy. I hope.
With a project like this, with delicate electronics that can easily get fried, I believe that having spare parts on hand is a good idea. The main board is pretty cheap: under $100, completely assembled, and the motors were about $30 each. We have spare stepper motors, spare stepper drivers, and a total of three main MaxESP OnStep boards.
Except that two of them (the ones we purchased from George C) don’t work at all, and I don’t know why. The one that Ken Hunter built and **donated** to us works just fine, after I did the required tweaking of various settings inside the Smart Hand Controller or SHC and inside a CONFIG.H file in the Arduino programming environment. And added the gears and belt.
I see almost no serious differences between George’s boards and Ken’s board. I am confident the problem is not my wiring or soldering, and it’s not the fact that George’s boards have RJ45 jacks, but what it is, I have no idea.
This is my second build of the connections between the stepper motor and the worm gear.
Without the help of Ken H, Howard Dutton, another Ken, Alan Tarica, Prasad Agrahar, and Khaled Bahayeldin, I never would have gotten this far. I am very appreciative of the amount of work that went into programming all of the many parts of the OnStep project as a whole. However, I found the OnStep Wiki rather confusing for beginners, and I hope to help them make it clearer in the future.
You can probably see that there is a good bit of wobble in the gears that involve the belts. That is probably because I failed to get the gears perfectly flush against the lathe chuck when I was enlarging their central holes from 5 mm to 1/4 inch despite using a dial indicator with a magnetic base to center it. I think I will need to order a new set of gears that have a 1/4″ axle hole already made at the factory. I don’t think I can do any better than I did, and that wasn’t good enough.
The reason for having the gears and belts is something to do with microstepping on the stepper motors that I really don’t understand. OnStep experts told me that the OnStep board, drivers, and steppers simply cannot handle gears that are 1 : 20 : 359. So we added a 3:1 toothed-gear-and-belt system so that the ratios are now 3 : 1 : 20 : 359. That set of ratios seems to make the steppers happy. (These motors have 200 steps per rotation, and are being currently driven at a rate of 1/16 of a step.) They don’t scream and stall any more, but the wobbly gears will probably translate into periodic error that one can see in the eyepiece or on long exposures with some kind of camera.
My next step is to take this entire apparatus up to the Hopewell Observatory itself and see what happens when I install them in the Right Ascension and Declination drives.
Then, we need to repair the electrical supply for the roll-off roof.
Then we have to put the telescopes back onto the mount.
Then, and only then, can we try having a “First Light” with the new motor pushing a very nice Ed Byers drive in an big, old, and very well-built university-grade telescope mount.
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