GoTo & Tracking Systems
|So, there I was, looking at my new 12” Dobsonian,
which is parked in the corner of the lounge, until I decided where it will
sleep on a more permanent basis. I made a point not to ask my wife's
opinion on this, as she is quite likely to suggest that the local landfill
site would be a good place. Needless to say a 12” scope is a sizable piece
of kit, and not the sort of thing most wives would delight in seeing behind
the TV or in the corner of the dining room !
I was also thinking how I'm going to modify the telescope and fit a GoTo system. I had converted two scopes previously to this one, my first was an 8” Helios reflector on an EQ3 mount. The second was a Meade LX50 10” SCT on a fork mount.
Both these systems were converted using parts supplied by Lenord Stage who runs GoTo and Tracking systems, which is in Arlington, Texas. I first spoke to Lenord a couple of years ago when I got the EQ3 mount and wanted to convert it to GoTo.
|Nobody did any sort of system that could be used on
such a mount, mainly because these are budget mounts I guess. But during
my search I found Lenord’s site. A few e-mails later and I knew I had found
the answer. A few weeks later when my system arrived I was not disappointed
- the system was excellent, and once installed worked brilliantly.
The later LX50 conversion went very well too; I put this down to the quality and versatility of the GoTo system because it can be used on just about any sort of telescope mount. Briefly, the system uses two stepper motors, which drive the mounts axis. The whole system is controlled by an electronics box. This is in turn connected via the parallel port to a small laptop computer. The electronics are supplied by Mel Bartels. The software used to control the whole thing is Mel's scope drive program, which has a number of different configurations and can be used on either a German Equatorial or an Alt/Az mount, depending on what you have.
So, as soon as I got my Dob home I emailed Lenord to ask about a new system. Unfortunately, I had to sell my first system along with the LX50, which had to go to make way for the Dob project. A few emails later revealed that Lenord had been working on a newly designed system for just such a telescope – the Evolution System.
My account of this installation is mainly from a DIY point of view. Lenord supports DIY in a number of ways, supplying most of the parts anyone might need to convert any number of different mounts. Back at his workshop he does the conversions himself and can supply a completely installed, fully set up and tested system ready to go “right out of the box”. This was pretty much what I got when I first did the EQ3 – Lenord supplied everything I needed and all I had to do was mount the motors etc. Lenord supplied information and advice which enabled me to do the installation easily myself.
For the Evolution installation, I already had a couple of stepper motors, plus some gearboxes, and a spare laptop. Lenord supplied a new electronic box, handpad, cables and the new Aluminum mounting plates and drive rollers that hold the motor / gearbox assemblies, and forms the basis of the new system.
If you are remotely handy in the DIY dept then you will have no problems fitting this system. It has been very well thought out and the quality of the components is very high. I was well impressed at the “kit” which Lenord put together for me, he even included the screws and washers and all the small nylon spacers for mounting the gearboxes. I was not surprised however at this level of service. My first GoTo system as supplied for the EQ3 was of excellent quality, right down to the coat of shiny black paint on the motors, and just as complete. Lenord’s work is of a very high standard indeed, and this is maintained whether you are getting a full installation or a DIY “kit” to install yourself. Everything you need is there, and well packaged too – when my Evolution system arrived it was wrapped in about ten miles of bubble wrap.
The Evolution system consists of two aluminum plates which hold the motor / gearbox. These are supplied with a drive roller for each axis which fits the output shaft on the gearbox – the rollers are splined in such a way that they act just like spur gears. The Az roller drives against the edge of the groundboard, thus turning the mount about the Az axis. This assumes you have a circular groundboard of course – unfortunately I didn't and so I had to make one before I could fit the AZ plates and drive. This wasn't that difficult and Lenord supplied information on how I should construct the new ground board, and the optimum size etc.
The other plate mounts on the Alt axis and drives the telescope via a strip of industrial Velcro, which is fastened around the Alt bearing. This requires that you cut a small ‘notch’ out of your mount just beneath the Alt bearing to allow for the drive roller, which sits just under the bearing.
The plates are designed so that you can engage/disengage the drive via a small lever. This pivots the whole motor/gearbox away from the Alt bearing or groundboard respectively. You can adjust the drive pressure exerted via a small screw – in practice this is a very clever arrangement, and works extremely well.
I had no problems at all with the Az drive onto the groundboard, this worked smooth as silk right from the start. The Alt drive worked fine too, but I had a bit of trouble getting the telescope to move smoothly at first, and so Lenord and I exchanged a few thoughts on this, until eventually we solved the problem. One thing about Lenord is that he will happily work with you, you are not abandoned once you get the equipment. Support is just an email away. I've lost track of the number of e-mails I must have sent Lenord in the time I've known him, but he always comes right back with an answer. He can usually solve the problem straight away.
The problems with the Alt drive were more the fault of the scope than the Evolution System. The Alt bearings on my scope are not particularly large, and of course it all depends on the construction of the original mount, i.e. how free it is etc., whether the tube is balanced. Lenord suggested I should try some small roller bearings instead of the Teflon Pads. As he suspected, there was too much friction - and sure enough this worked a treat. The scope then moved smoothly with no problems. I believe that scopes with larger Alt bearings will not suffer from this problem. I also discovered that the tube was in fact out of balance, which probably contributed to the original problem. So this was dealt with as well and a few weights were strategically placed to bring the tube into balance.
Setting up the system is fairly straight forward, once the installation of both Alt and Az plates is complete, and both axis drive smoothly using the motors. You will need to tell the software what your final drive ratios are. This is easy and there are full instructions on how to do this on Lenord’s site. In a nutshell, all that's needed is to attach a cheap laser pointer to the mount, point the laser at a nearby wall or ceiling and make a mark where it is shining. Then move in Az via the motors one complete turn, until the software says it has moved through 360 degrees. The pointer should be right where it started. If it is not, then you adjust the stepsizes in the software until you get the pointer back where it started after one full turn.
The Alt is even easier, all you need is a precision level. You then level the tube and then move it via the motor until it has traveled exactly 90 degrees. The software will show how far the tube has moved on the laptop screen. When the software says 90 Deg., check the tube with the level. If it is not exactly 90 Deg., then again you must adjust the stepsizes in the software until this setting is correct. In practice you soon get used to doing this and it is not difficult to do at all, but time spent here will pay dividends later as this is the key to good pointing accuracy.
Once I had the stepsizes set, I then set up the backlash – again there are full instructions on how to do this available on Lenord’s site. It is easy to do, but again you need to be as accurate as possible with these settings as this will also affect pointing accuracy.
So – installation complete and ready to test under the stars, fortunately I didn't have to wait too long for a decent night for the first test. I started out by leveling the tube and pointing it South. Then you need to reset the system so it knows roughly where it is, and pick a couple of bright stars to align the system. Anyone who has seen or used a GoTo telescope will be familiar with this type of set-up, as most GoTo scopes are similar in this respect.
I keyed in my alignment stars, and once done I selected my first ‘GoTo’ object, which just happened to be the Andromeda Galaxy simply because I finished my alignment on Deneb in Cygnus, and this was the nearest object that sprang to mind at the time.
The motors hummed sweetly, and the scope smoothly slewed around and then stopped. The software then corrected for backlash and tracking came on. I stepped forward to peer into the eyepiece, and there roughly central was the Andromeda Galaxy. I next keyed in Saturn, which was right across the sky and roughly 180 degrees away, again the motors hummed and the scope smoothly slewed around. When it halted I peered into the eyepiece once again, to be greeted by Saturn, well within the central portion of the field of view. I was delighted with this first test, and I have since used the telescope a further twice with very similar results.
I would give the Evolution System a big thumbs up, it is a quality system, easy to install, and is just as accurate as the previous systems I have installed – a big ten out of ten in my book.
Conversion design by Lenord Stage
GoTo & Tracking Systems
5000 Green Hollow Dr.
Arlington Texas 76017-5910