A decade or so ago, I bought a brand-new Personal Solar Telescope from Hands On Optics. It was great! Not only could you see sunspots safely, but you could also make out prominences around the circumference of the sun, and if sky conditions were OK, you could make out plages, striations, and all sorts of other features on the Sun’s surface. If you were patient, you could tune the filters so that with the Doppler effect and the fact that many of the filaments and prominences are moving very quickly, you could make them appear and disappear as you changed the H-alpha frequency ever so slightly to one end of the spectrum to the other.
However, as the years went on, the Sun’s image got harder and harder to see. Finally I couldn’t see anything at all. And the Sun got quiet, so my PST just sat in its case, unused, for over a year. I was hoping it wasn’t my eyes!
I later found some information at Starry Nights on fixing the problem: one of the several filters (a ‘blocking’ or ‘ITF’ filter) not far in front of the eyepiece tends to get oxidized, and hence, opaque. I ordered a replacement from Meier at about $80, but was frankly rather apprehensive about figuring out how to do the actual deed. (Unfortunately they are now out of stock: https://maierphotonics.com/656bandpassfilter-1.aspx )
I finally found some threads on Starry Nights that explained more clearly what one was supposed to do ( https://www.cloudynights.com/topic/530890-newbie-trouble-with-coronado-pst/page-4 ) and with a pair of taped-up channel lock pliers and an old 3/4″ chisel that I ground down so that it would turn the threads on the retaining ring, I was able to remove the old filter and put in the new one. Here is a photo of the old filter (to the right, yellowish – blue) and the new one, which is so reflective you can see my red-and-blue cell phone with a fuzzy shiny Apple logo in the middle.
This afternoon, since for a change it wasn’t raining, I got to take it out and use it.
Two days ago, Joe Spencer had first light with the 6″ f/8 Dobsonian he built in the DC-area amateur telescope workshop. He worked hard on this project over more than a year, including grinding, polishing and figuring his mirror, and it seems to work very well.
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!
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.
I think I have succeeded in getting our OnStep build to work properly. Previously, whenever I asked the drive to slew to an new location, the stepper motors would build up to a certain speed and then stop rotating while they screamed, seemingly in protest. It’s called stalling.
With the help of several of the principal leaders in the OnStep project (Howard Dutton, Ken Hunter, Khalid Bahayeldin) and Alan Tarica and Prasad Agrahar, I think I may have finally got the settings set properly. The final secret was to reduce the slewing speed in the smart hand controller to the lowest setting.
This does make slewing rather slow, however. To go from the location of Jupiter to Capella tonight, which is a pretty long distance across the sky, took nearly eight minutes. Watch the video.
About a week week ago, the right ascension (or RA) drive on a vintage mount at the Hopewell Observatory stopped working. Instead of its usual hum, it began making scraping noises, and then ground to a halt. (This drive is the one that allows one to track the stars perfectly as the earth slowly rotates.)
Another member and I carefully removed the drive mechanism, and I took it home. At first, I thought it was the motor itself, but after examining it carefully, I noticed that some clutch pads inside the gearbox had come unglued, causing the clutch plates to be cockeyed. The motor itself worked just fine when disconnected from the gear box.
I recalled that the pads and the clutch had been very problematic, and that our resident but now-deceased electro-mechanical-optical wizard Bob Bolster had had to modify the gearbox quite a bit. I carefully disassembled the gearbox and used acetone to remove all the old glue that he had used to glue the pads on. After doing some research to find some equivalent pad material, I yesterday ordered some new gasket material with adhesive backing from McMaster-Carr. Lo and behold, I received it TODAY! Wow!
I cut out new pads, re-assembled everything, and the gears and worm drive work just fine. Not only that: there were no screws or nuts left over!
In addition, I now see how we can replace the extremely complicated partially-analog clutch-and-drive mechanism, in both RA and in Declination with a much simpler stepper-motor system using something called OnStep.
Here is a photo of the some of the innards of the scope:
A bit complicated, no?
In the next photo, my pencil is pointing to the clutch pads inside the gear box that had come loose, causing the clutch plates to become cockeyed, jamming the gears. The clutch is so that the observer can ever-so-slightly tweak the telescope forward or backwards in RA, in order to center the target. There is another gearbox for the declination, but it’s still working OK, so we left it alone.
The synchronous gear-motor in the background. My pencil is pointing to the problem.
Of course, we still have to re-install the gearbox back in the scope.
Bob Bolster, mentioned above, was one of the founding members of the Hopewell Observatory. He was an absolute wizard at fixing things and keeping this telescope mount going, but he is no longer alive. I was afraid that I would not be able to fix this problem, but it looks like I’ve been successful.
I append an image of a very beautifully-refurbished Ealing telescope and mount – similar to the one owned by Hopewell – that belongs to the Austin Astronomical Society. Ours is so much more beat up than this one that it’s embarrassing! Plus, both we and the University of Maryland were unable to get the telescope itself, which is a Ritchey-Chretien design, ever to work properly. So we sold the mirror and cell to a collector in Italy for a pittance, and installed four other, smaller scopes on the mount instead.
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