The interest of measuring the DEC axis motion (Y), at the same time as RA motion, is to show that the oscillations due to turbulence are identical, and that the Direct-Drive system does not produce any spurious oscillations on RA axis. Both axis are driven by a closed loop servo system running at 10 Khz. Followers 1. The sidereal rate was set as best as possible (731.15 / sec) and a good DEC telescope optical tube balance. http://www.astrosurf.com/cavadore/technical/Directdrives/, http://ro.uow.edu.au/cgi/viewcontent.cgi?article=2339&context=theses, http://www.siderealtechnology.com/DirectDriveWorkInProgress.pdf, http://planewave.com/technology/mechanical-design/, https://www.youtube.com/watch?v=bCEiOnuODac, https://www.pololu.com/file/download/drv8825.pdf?file_id=0J590, https://umexpert.um.edu.my/file/publication/00005177_68575.pdf, http://eprints.whiterose.ac.uk/863/1/zhuzq5.pdf, http://web.mit.edu/kirtley/binlustuff/literature/electric machine/designOfAxialFluxPMM.pdf. The curve is noisy because of the tip tilt motion of the star due to the turbulence, the exposure time is 1/400s. … If you click over the image, a DivX video at 15 frames per second will be shown : The position of the Airy disk is measured 4 times per second, X is RA and Y is DEC: it is possible to show the tracking errors if they exist. Nevertheless, tests shall be performed on sky to validate system performance. The direct encoder readings provide system performance monitoring. Direct Drive Mont: Les supports ont un entraînement direct DDM entraînement direct avec des moteurs à couple élevé dans RA et DEC. La précision de fonctionnement de ce montage est si précis qui peut être distribuée à un suivi (Guiding). It's easy! This is a NOVA 120 mount plus a 20" RILA F5 (weights 100kg) Another 500 mm Telescope located in Chile (SpaceObs San Pedro Atacama) … However it could be I'm looking at the wrong. Here is a windowing on the center of the camera, which clearly shows the Airy disk of Arcturus (1/2000s Exposure). the key here is to have the magnets not backed by iron/metal but in slots instead. STEPPERONLINE Short Body Nema 17 Bipolar Stepper Motor 1A 18.4oz.in/13Ncm DIY CNC Extruder 4.5 out of 5 stars 167. This is useful given that good weather is pretty rare in my home place. The Stellar Cat system is a complete electronic control package allowing the control of a telescope using either a Sky Commander or Argo Navis Digital Setting Circles as the reference. the poles) move. The Dob is simpler to build...that's one reason why it's so popular. onsumption may increase to more than 100W in this mode. See more ideas about telescope, telescopes, amateur astronomy. Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Without gears, and just the bearing to worry about, the concept of backlash is removed. This will drive another Bayside gearbox, this one 3:1 and then that will drive a 80:1 harmonic drive which will have the saddle for the telescope on it. $132.00 - $234.00 #13. I realize it is difficult to verify these points and may be limiting the system .... A late night with a seeing between 2 "and 3" arsec seeing was measured. * direct drive magnetic coils to create flux mounted fixed to the mount casing, these are grouped into phases. The power consumption of the system in sidereal rate is about 5 to 10W: no more. Nowadays, this solution is starting to enter the small telescope market because of costs reduction and very good performance parts like encoders and brushless motors.... A demonstrator allowing me to evaluate the way of making this system real and performing according my specification is being presented thru this page. the length of the telescope etc. Copyright © 2021 Stargazers Lounge The worst is the image 2 which presents an elongation of 27% of stars on the delta axis. £24.19 postage. Here are 4 out of the 7 images (X-axis is the RA axis alpha, and Y is DEC) If a pointing model coupled with an active correction RA/DEC speeds would have been used, the error could be even lower! The tracking regularity was measured with a DMK41AU camera (4.65μm pixel size) using a simple Ø180mm INTES telescope having 1800 mm of focal length. This allow to get very stiff and very responsive axis to the wind. The complex is to make calculations to cover all eventualities and the simple&fast is to make a looped control system fast enough to control (same occurs with hydraulic control systems as the oil heats up/cools over time making it even more dynamic than a motor). 1. Yes I've noticed some suppliers give temperature ranges for different grades of magnets. This prototype allows me to learn of lot on this topic, even this is just concerning a single axis. If you look at this: http://planewave.com/technology/mechanical-design/ you will see what is a three phase coil system. I can see what you're saying in terms of flux holding and then accelerating and decelerating - this is close to what a stepper does. This mount can track in Alt-Az and Equatorial modes. Good luck with your project. The Orion AstroTrack Drive works with Orion EQ-1 or Min-EQ equatorial mounts. If you add and stack all images, it lead to a final 35 minutes exposure and the image quality is quite honorable. The night of March 4th, 2010 was less turbulent. It is a feature which we have studied the issues and does not shows any issues to integrate. This is probably the combined effects of bad polar alignment and a not perfect sidereal speed (estimated to 0.013%). In the so-called "good old days" if you built your own telescope, you generally made an equatorial mount to go with it. It is located at RA = 15h30m25s and DEC = 4 ° 00'30" I'm guessing that the voltage is require to allow the motor to overcome any EMF etc. Well, neodymium magnets, magnetic linear tape and “enamelled” copper wire are easily obtained. It doesn't show much and the links I have found in the past have decayed.. so starting at the beginning from scratch may be the better option. How do you drive a bipolar stepper? Well, you just hook up a couple of H-bridges and let the microcontroller switch them. This is always going to mean a compromise. The worst is the image 2 which presents an elongation of 27% of stars on the delta axis. If a pointing model coupled with an active correction RA/DEC speeds would have been used, the error could be even lower! A bi-polar stepper is a two phase system where the flux is managed (in realtime) to move the 'step'. At the moment focusing doesn't and the mount will always be an approximation for the moment to track the star. The scale is 0.18 "per pixel: this is a high magnification. Per kindly shot a hole in that idea as it stood because of alignment of the bearing. For the time being, only the RA axis has been modified, the DEC has still a worm and a gear. There are no RA oscillations due to the direct drive engine system. Jul 19, 2020 - A home built equatorial mount for my telescope built mostly recycled components I have had lying around. Hmm seems my previous post disappeared in the mobile either.. The equatorial is more complicated, but still not out of the question even for those with just basic tools. Saved from hackaday.io. Low yield : drawing lot of current for a slow motion. The cause of this defect is unknown. In fact having the magnets side on may produce a weaker field but more oscillations between North and South poles. However using a prospex/acrylic disk with could be used, and I think I have a couple designs that could make it usable. Power tools – A plunge router for cutting the circular components of the mount; hand drill with 1.5mm and 2mm bits to make pilot holes.. Powered by Invision Community. Noisy overnight, especially with the use of stepper motors that can resonate with the telescope mount. Find out everything you need for set-up, software, Although you won't have backlash to deal with, you'll still have the inertia of the moving mount to overcome and I don't think you can model that to sufficient accuracy to stop the mount exactly where it is supposed to stop - not without some form of closed-loop: encoders or the like. By adding exposure #1 with exposure # 7 without registration, it is possible to see the difference in RA and DEC over 35 minutes: The RA offset is 5.1 pixels (4.2 "or 0.12" / min) and the DEC offset is 17.1 pixels (14.3 "or 0.4" / min). The curve is noisy because of the tip tilt motion of the star due to the turbulence, the exposure time is 1/400s. The night of March 4th, 2010 was less turbulent. We have placed cookies on your device to help make this website better. Valmeca achieved the mount modifications. This mount has been developed for large Cassegrain telescopes and Hypergraphs from 24" aperture onwards, but it is also a perfect match for long and heavy refractors like our large APM-LZOS apochromatic refractors. NickK, May 29, 2016 in DIY Astronomer. View of the encoder and the read head, it is highly accurate. It also allows fine adjustment of parameters of the PID controller which manages the encoder and motor. A loosen type brake when not current is going through a coil is easy to implement. The closed loop is: Position / desired movement -> three phase power configuration -> movement. This technology is employed in modern professional telescopes. APM GE-300 (Direct Drive) Our professional APM GE-300 mounting starts at a point where the carrying capacity of other mountings is too low. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. DIY Harmonic Drive Equatorial Mount. Click & Collect. DIY Harmonic Drive Equatorial Mount | Hackaday.io. . Mechanical Travel Mount Autoguider for Astrophotography with DSLR and Lightweight telescopes 4.4 out of 5 stars 181. $16.99 … It was also impossible for me to change the programming or maintain the system. A Fourier spectral analysis on RA axis motion would show any preferred frequency of oscillation: Spectrum shows only noise, this means that no preferred frequency oscillation is occurring. But it is still a drift and slow, which is not polluted by any periodic oscillation error. Sensitive to wind gusts, especially in DEC axis. The details about force, acceleration, deceleration etc are all done within that loop. One must keep in mind that the encoder is relatively distant (RA bottom axis) from the optical tube. And, if something happens to your mount, such as drives failing, purchasing replacement parts in order to keep the Go To unit can add up. Nothing like the monster you're attempting though! Dozen of outstanding images have been recorded by this setup with a 500 mm Newton telescope. If you click over the image, a DivX video at 15 frames per second will be shown : The position of the Airy disk is measured 4 times per second, X is RA and Y is DEC: it is possible to show the tracking errors if they exist. A direct-drive system is composed of a threaded rod pressed against the rim of a large drive circle. After some poking and googling I was able to determine that the mount uses a bipolar stepper motor to compensate for Earth’s rotation. DIRECT DRIVE. Integrated direct drive mount with optical encoders, zero periodic error, zero backlash, and minimal maintenance due to the lack of gears. Look at the sine waves, the mechanism for the direct drive isn't much different. However with more coils, the net effect is the same (although the more copper.. and less power results perhaps in less efficiency). It has 7.4µm pixel size and lead to a 0.89 "plate scale with 1700 mm focal length. Just been thinking about the encoder - previously I've looked at using optical fiber as a rotational inferometer. The yellow area shows where 90% of measured points are located from the DirectDrive system for comparison. The L-350 is a great option for any astronomer looking to get the absolute most out of a 14-inch aperture or smaller telescope. Explore. Very poor performing when dealing with very small back and forth movements, the back-lash can be very complicated to compensate. Depending on what you choose to do, you can completely automate your scope for somewhere … 7 exposures of 5 minutes (300s) have been achieved with this camera and the telescope. The result is that you should get higher granularity. Mechanical wear of part involved in movements. The pixel scale is about 0.53 "per pixel, this level allows to see any flaws. Pioneered by John Dobson in the 1960s, the instrument combines a Newtonian reflector telescope with a unique two-axis movable base. ServoCAT GOTO Drive. There are several ways to build a telescope mount drive (including manufacturing your own precision worm gear – check out this DIY build from the Curdridge Observatory!) Here is the first plot showing 3 measurement per second during 10 minutes: The Y scale is expressed in arcsec, and does not show during 10 minutes. Do we need an encoder? Software compensation of telescope hysteresis; Control-, Pointing- and Tracking-Software included in delivery; The mission over the past few years, has been to develop a new mount with similar tracking technology used by professional Observatories, and offer that mount at a fair price. So the star oscillations are only due to turbulence and the Kolmogorov turbulence statistics and spectrum. This is another link I have seen in the past: http://www.astrosurf.com/cavadore/technical/Directdrives/, http://electronix.ru/forum/index.php?act=attach&type=post&id=66372, http://www.astronomyasylum.com/directdrivemotor.html, https://www.dropbox.com/s/4tml2d83k8okj86/Project-HET615-OrlandoAndico.pdf, http://wvi.com/~rberry/calpoly18/bulletin07/bulletin07.htm, Flux: http://ro.uow.edu.au/cgi/viewcontent.cgi?article=2339&context=theses, Sidereal's tech - interesting diagram showing the phase control PWM: http://www.siderealtechnology.com/DirectDriveWorkInProgress.pdf. I pointed toward a field near to the celestial equator (DEC ~0 °), who represents the area where errors are most visible (no attenuation by the cosine of the declination). In all cases, the periodic errors of worm and gear (see here measurements from many worm and gear equipped mounts) are completely absent. (see here measurements from many worm and gear equipped mounts). or Best Offer. Integration has been achieved in a modified VMA-200. It also allows fine adjustment of parameters of the PID controller which manages the encoder and motor. * a mechanism to provide positional feedback as the mount shaft moves - question is.. could a sensing system be good enough to maintain position with power? Threads are impressed into the rim of the drive circle either by JB-Weld, wood putty, or fiberglass. In what follows, other UNGUIDED tests were performed using a SBIG ST-2000 camera (optimized for deep sky imaging). Parameters - GEM mount otherwise i'll need to make a rotator. It uses a primary mirror to capture and reflect light, a secondary mirror to direct light into an eyepiece, and a focuser to make fine adjustments for viewing. This system has the simplest mechanical configuration. I still have the power point presentation (2007) by Dave Rowe (Starry Ridge), who created a 3 phase direct drive. Are you going alt-az (With image rotator) or GEM? Feedback is via encoder tape. It precisely controls the telescope's tracking speed during long, timed exposures of celestial objects, producing the best possible image sharpness. This gives me stupidly high resolution of 31,457,280 steps per rev. The difference is that the stepper applies X force (I wrote a ardunio chopper micro stepping driver) and that is static (as it assumes the stator moves inline with the step). Magnets and coils shaped as wedges result in better performance due to the flux resulting. A direct drive system directly connects the armature of the servo motor to the driven axle. If the same FFT plot is carried out with the DEC axis motion data, there are no peak frequency, this is only noise. One thing to note - a DVD or CD has too wide pulse widths for encoding, instead a bluray laser would be needed if you wanted to use a small diameter disk. The number of coils/magnets in the three phase arrangement and their placing far away from the axis of rotation is what make accurate control possible. ASA Product Folder. STEPPERONLINE Nema 14 Motor Step Motor 1.8deg Bipolar 12V 0.4A 14Ncm/20oz.in 35x35x26mm 4-Wire 4.6 out of 5 stars 18. 7.4µm pixel size and lead to a 0.89 "plate scale with 1700 mm focal length. The part of the telescope that connects to the mount is called the dovetail. 2. Spectrum shows only noise, this means that no preferred frequency oscillation is occurring. Stator (right) and rotor engine (left), the two are intertwined rings and mounted directly on the RA or DEC axis, the engine is 210 mm in diameter and provides high torque, As the RA axis has encoder whose resolution is about 0.02 arcsec per steps (nearly 63 million steps per revolution), and it is a closed loop system, it is quite possible. So I'm going to start researching options for doing a Direct Drive mount to hold a 4" APO with a couple of cameras.. The forces involved being dependent on the amplitude of the desired movement. Buy telescope motor drive and get the best deals at the lowest prices on eBay! The first RA measurement shows that the standard deviation of the motion is 0.79 arcsec. By using this site, you agree to our Terms of Use. Since I was starting from scratch, it was too risky to change the two axis at once. I decided to make my own telescope control system from the ground up and the Arduino platform seemed the obvious choice. They can be used to control either a Dobsonian or an equatorial mount telescope. The tracking monitoring was measured with DMK41AU camera (4.65μm pixel) using the same Ø180mm INTES equipped this time with a 3x barlow, providing a 5400 mm focal length. Here is a windowing on the center of the camera, which clearly shows the Airy disk of Arcturus (1/2000s Exposure). This could be possible to add encoders in both RA and DEC axis, leading to better performance, but this is rather expensive. The polar alignment shall be careful ... One must keep in mind that the encoder is relatively distant (RA bottom axis) from the optical tube. 7 exposures of 5 minutes (300s) have been achieved with this camera and the telescope. I’ll follow this with interest. Saved from hackaday.io. Even ASA had a lot of trouble getting their DDM mounts to market and working anything like properly. The telescope attaches to the mount via the dovetail being clamped down by the saddle, which has knob tightening screws to hold the telescope securely in place. Check out images here L.Bernasconi and M.Meunier. There is a link to a document with constructional details of the motor here: http://www.altazinitiative.org/AA Tech & Demo.htm. The tracking regularity was measured with a DMK41AU camera (4.65μm pixel size) using a simple Ø180mm INTES telescope having 1800 mm of focal length. SpeedDrive documentation Update6 -- EZR Struder now supported thanks to user Garigen Update5 -- Geeetech A10 now fully supported thanks to user Cyg0r3 Update4 -- Ender 5 now fully supported thanks to user paydayxray and user stijoh Update3 -- Redrex geared extruder now supported thanks to user huubert. In all cases, the periodic errors of worm and gear, Maximum pointing speed and axis stiffness, It has been tested a high speed of 20°/sec, the next video, we started with a 4°/sec speed and going up to a speed of 20°/sec. The interest of measuring the DEC axis motion (Y), at the same time as RA motion, is to show that the oscillations due to turbulence are identical, and that the Direct-Drive system does not produce any spurious oscillations on RA axis. Each drive has two long arms and a lead screw to push the arms away from each other. After that everything else is below that because of the close loop control. I believe that direct drive mounts don't "move" in discrete steps, they accelerate the mount and decelerate it. FAST & FREE. This experiment demonstrates how the axis and its engine are rigid. DIY Astronomer ; Researching - Direct Drive mount Facebook; Twitter ; Stargazers Lounge Uses Cookies. The telescope itself was dusty and wet, but the mount was in a good shape, just the driver electronics for the motor were missing. Add a washer and a nut (M10) to tighten the wheel. A good telescope mount is the bedrock upon which any decent observing or astrophotography setup is built. Therefore I do not have to design in much portability. This prototype allows me to learn of lot on this topic, even this is just concerning a single axis This curve look less noisy due to the laying of 2s per point: the effect of tilt tip star turbulence is smoothed. Go To computers are specific for each mount — meaning they aren’t interchangeable. This cordless, precision DC servo drive allows motorized tracking of objects in space as they appear to migrate across the night sky due to Earth's rotation. Olly would dispute whether they work properly even now! Valmeca achieved the mount modifications. The stiffness and the smoothness must be derived from high resolution position feedback. In the MIT paper it indicates the spacing between flux for the magnets and coils (iron), this shows the reason for using more magnets than coils - the thinner magnets means less flat spots in the waveform that result in dead spots and so more efficient. This project focuses on gaining remote computer control of a Celestron telescope mount, as well as adding the ability to use a more ergonomic joystick for slewing while at the scope. Encoders have limited resolution and interpolation of the signals has to be done. From my experience with the focuser + 100:1 gearbox to a 1:1 connect to the rack and pinion - that's the key calculation. Telescope mounts have a part called the saddle, which is where the telescope connects to the mount. If the same FFT plot is carried out with the DEC axis motion data, there are no peak frequency, this is only noise. The results are rather good: the images are sharp, and the elongation of the stars below 20%. This is especially important for slow moving drives as the duty cycle for each coil seems far higher and so the current has time to increase the temperature naturally - causing a heating effect on the magnets within close proximity for that time.