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CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.
Vixen SS 2000 PC - GOTO system...and a "tweaked" Synta CG-5/EQ-4 mount
Previously I had obtained one of the Chinese 6" achromat refractors and German mounts made by Synta and distributed by various companies with their company name and colors on the tube. Orion, Celestron, Bresser, SkyWatcher are just a few of the companies importing the Synta telescopes and selling them under their own company name. The intent was to use the telescope with an Aries Chromacor adaptor. I previously reviewed this very effective piece of optical magic for CloudyNights.com. I have since found the Synta/Chromacor to easily match many high end telescopes and the resulting telescope was so impressive that it warranted either improving the existing mount or replacing it with a better one.
The telescope package included a German Mount also made by Synta. If you buy the Celestron version of the telescope it is called the CG-5. Other dealers will list it as a EQ-4 (Syntas own designation). The mount is a clone of the Vixen Great Polaris Deluxe. While there are some areas for improvement on that mount, it is within the average handypersons ability and for the price it is hard to beat it. I have pulled it completely apart and it has decent workmanship, dual ball bearings in the RA axis and brass worm gears on both axis.
Originally I thought I would sell the mount (included with the package and the telescope wasn't available without the mount at the time) and get a heavier duty mount. I decided it might be worth it to see if I could improve the mount with some tweaking before getting rid of it. After reading some hop-up-tips of some other people I figured that it would be worth the effort.
The biggest change recommended by all owners was a replacement of the stock aluminum legs with heavier wooden legs. The stock legs may be sufficient for a lighter scope but with a heavy/long 6" refractor it was far beyond its capabilities and shook like a bowl of Jello at the slightest touch or breeze. I replace the legs with some massive home made hardwood legs utilizing the stock aluminum upper mount and the stock tripod spreader. While it is a relatively easy task if you have access to some power tools…there are ready made replacements available from several sources such as HandsOnOptics.com. The wooden legs made an amazing transformation. The scope became one of the most vibration free/solid mounts I have owned. A hard thump was quickly and completely damped out in less than a second.
Next came the tweaking of the German mount itself. The hop-ups to these mounts is well known and documented throughout the various internet newsgroups. Suffice it to say that the fixes included replacement of the stock ultra thick grease with a lighter grease, adjustment of the worm gear axle side to side play and adjusting of the gear lash. There is quite a bit of fine tuning capability provided in the mount..sadly not much is described in the owners manual…or what passes for a manual. A huge performance increase was experienced when I replaced the stock small rubber O rings that are used as compression rings on each side of the worm gears with nylon O rings. These eliminated ALL excess side to side axle play and torque induced twisting of the axle under heavy load.
Originally I used the Celestron Dual Axis drive system. This is a pretty simple, relatively cheap ($165) and unsophisticated setup that worked more than adequately for visual use and occasionally for guided film imaging. The maximum slewing speed was not that fast, there was no provision for periodic error correction or back lash compensation. The lack of backlash compensation made it far more difficult to do guided imaging…but it is possible. The average owner may be happy with this setup…but I kept hearing great things about the Vixen Sky Sensor 2000 PC- GOTO system.
I attended one of my club's star parties and had a chance to see the setup in action by one of the members and was impressed. The decision to get the unit for myself was made when I realized that Orion (the US distributor) had a great money back guarantee…and they told me that it was a direct bolt on to the EQ-4/CG5 mounts. A little over $900 later I had one and over the next few days fell in love with it. The few Synta parts that are marginal are not used in the conversion so that is a big plus.
When installing the unit it became obvious how closely the Vixen GP-D was cloned by Synta. The unit was a perfect fit in every way, screw holes perfectly lined up, contours matched…even the gear ratio was correct. The installation took no more than about ½ hour. I was impressed with the quality of the unit, motors and housing which are very nice aluminum castings that match the Chinese mount perfectly visually. The motors are big beefy servo motors of the low cog variety.
The unit runs on 12 volts DC which made me VERY happy as all of my other scopes run on 12 volts so I can power everything from the same marine deep discharge battery. The hand controller is on the large side...but well laid out. It also has a connector on the side that you can connect a lanyard. I normally have one and hang it around my neck so I can take my hands off the controller and still have it handy. There is only one cable from the controller that splits into three cables. One of these wires goes to the power source, one to the RA socket and one to the DEC socket.
OK…what makes this unit so great…let's run through just some of its features. First…for you computer geeks…it has a 32 bit RISC processor instead of the 16 bit or 8 bit processors in other GOTO scopes. All that huge increase in number crunching ability is put to good use. I should mention that at the same time I took delivery of the Vixen…I also bought a Celestron Nexstar 11" GPS telescope. While that scope is nothing short of amazing I have to admit that the Vixen even tops THAT scope in features and capability.
No this isn't a GPS capable drive system…you need to enter you date/time/location longitude and latitude. But that is about the only concession it makes. Once you have the Latitude/Longitude for all your favorite sites you can input up to 10 of them in permanent memory. The ability to input alpha characters means you can label these so you know what you are looking at in the future. The display is black quartz letters back lit so you can see it in bright sun as well as at night. The actual brightness of the display is adjustable over a 10 stop range or turned off. To start the telescope you rotate the scope in DEC and RA so that it is parallel to the ground and the optic end is facing East. When you go through the alignment process it slews to the first of up to three stars. Once it quits slewing you use the buttons to exactly center the star and align it. It than proceeds to the next alignment star. Of course like any GOTO scope it is best to start with the tripod bubble leveled for the best whole sky performance. This may sound similar to alignment on other GOTO scopes…but even here the extra capabilities are utilized. The alignment process knows that as you get closer to the horizon the stars will be diffracted by the atmosphere and allow for that.
Once aligned you just select your objects from the 14,942 object database and it goes to it. While the 14,942 objects may not sound a lot compared to the 40,000/100,000 object data bases of the latest offering from Celestron/Meade. But the Vixen has really USEABLE objects. It has all the Messier objects, all the NGC objects and all the IC objects, and the SAO objects over mag. 4.0. The data base has an extensive description of most objects which is handy. One feature that is really slick is the listing of 138 surface features on the moon. You can use a crosshair eyepiece to center on one feature and than it will slew to the other moon features on the moon. In addition you may wonder which of the 4 moons around Jupiter you are looking at…each is a separate object so you slew to each moon you are looking at without consulting charts. If you wish you can directly enter the coordinates of an object and slew to that.
You have a solar block out feature that prevents the scope from slewing into the sun and that can be turned off if you want to observe the sun. It also has the ability for the user to input the orbital elements of any satellite in the user memory which holds up to 30 satellites, 30 comets, 60 user objects and 30 land objects. Once a satellite is entered when it comes into view…the hand controller will signal that something is coming into view and asks you if you want to see it. If you do it slews to it and tracks it!
GOTO accuracy was extremely accurate…it had no problem placing any object in the center 1/3 of the FOV of a
14mm eyepiece. It also has the Vixen version of Meades High Precision Pointing which is handy for extremely faint
objects and to ultra refine the pointing accuracy. This is especially handy for CCD or film imaging where you can't
see the object with the telescope…you need a long exposure image to capture it. If you need to refine the alignment
throughout the night you can do a realignment but I found that it was so accurate this was rarely needed.
When I first got the unit I spent some time trying to figure out how to tell it to go to solar, sidereal, or lunar tracking speed. After reading the manual I found out that it automatically knows what object it is looking at and selects the correct speed. In addition I was impressed with its actual ability to adjust the RA and DEC tracking speed based on its proximity to the poles. Other telescope drives select one clock speed for sidereal tracking and use that all the time. But this is inaccurate. The Vixen computes the angular displacement from the pole and applies the correct speed to the RA and DEC axis independently to ensure accurate tracking of the object.
The user utilities have a wide range of tweaks and preferences. You have backlash compensation in all directions, Permanent Periodic Error Correction, and user settable speed settings. There are 4 various choices for tracking/slewing speed. Each is settable to the users taste. In addition the fastest slewing speed is variable and can be set with a ramp up and ramp down accelerate/decelerate speed. This is great for big scopes as it softens the shock to the gears as the scope starts and stops. In addition the fastest slewing speed can be quickly let off and than back on as it comes down and it will than slew at that speed. This is how it provides a variable slewing rate. The top slewing rate is factory set at 1200x but can go up to 1999x which is about 8 degrees a second…pretty fast. The noise when slewing is not bad. It is only relatively loud at the fastest slew speed and if you wish you can select a slightly slower top speed to reduce the sound. In any case I found it far less obtrusive than Meade LX-200s or Astro Physics GOTO mounts.
OK…once aligned in what they call Unaligned Equatorial mode you are ready for visual use. But suppose you want to do some photography…how do you polar align the scope? No need for a polar alignment scope or even star drift unless you want an ultra accurate setup. Instead you do a three star align and than from the utility select Polar Aligned Equatorial mode while while perfectly centered on a star near the equator. When you do the scope will drift away from the star and stop. That is the difference between your alignment and the true polar alignment. You than use the ALT/AZ screws on your mounts controls to center the star and you are polar aligned! What a slick trick!
There is a tour mode that will go through the various objects visible that night/time/observing location. It will allow you to manually step through the objects…or you can set a time to pause at each object…will slew to it, let you look and than slew to the next item.
It seems to do quite well avoiding the tripod legs and dealing with flopping over center as required. Occasionally I did need to hit the stop button to avoid the long refractor from hitting the tripod leg. I would slew manually to get around the object and than hit GOTO again and it would continue to the object. A shorter telescope or if it were mounted on a pier would avoid this possible conflict.
The stock Celestron dual axis drives utilize clutches (which were a pain to use). The Vixen doesn't use any clutches and I was concerned if this would be a problem. Turns out that you don't need them….if it runs into something it just stops and tells you to clear the obstruction and start again.
You can select from 4 telescope motions/readouts including RA/DEC, J2000 (RA/DEC to Epoch 2000), X-Y and ALT/AZ. The readout also includes local time, sidereal time, a built in count up or down timer.
Another slick trick is the Identify mode. Other telescopes will ask you to aim at something and they will search their database for that object. The Vixen search is user selectable by choosing the radius of the search. For instance…you might set an area included in a 2 degree circle…it will search its database and any objects found will be listed. It will tell you it found so many objects and you can than page through them until you find one you want to go to or just hop from one to the other to see everything in that area.
The Vixen includes the connecting cable that runs from the hand controller to a computer running software like THE SKY. I have that software on my laptop and find it works flawlessly with the Vixen. The Vixen gives you the option of emulating either Celestron Ultima 2000 or a Meade LX-200. I tried both (you also need to set the matching virtual computer from THE SKY). Both worked however the Meade emulation also enabled several additional capabilities. I was able to realign from the controller, put the scope in Sleep mode or Park. You have the option of running the telescope from the hand controller or the laptop. With the laptop you have a huge database of GOTO targets. Just find one and hit slew…and it happens with on screen tracking in real time.
OK…here is the last really slick trick. Supposing you need to power down the Vixen for some reason. As long as you don't move the telescope mount or release the mounts main clutches…you can restart it up and it is still perfectly aligned. All you do is turn it on and instead of going through the alignment sequence you just escape out of it and you are back in business.
I currently am running my 6"- f8 refractor with a 2" AP diagonal and one of my Pentax XL eyepieces (read heavy), some additional lead weight to allow the telescope to be pushed farther up in the rings (less eyepiece swing) plus the Chromacor. This makes a total load of 24#. Not only does the Vixen handle this load without a problem…I have piggybacked my Tele Vue Pronto on as a guide scope for film imaging. In this configuration I am running at 30# and it still works fine. Pretty impressive! I haven't quantified the periodic error yet but it appears to be in the same range as my Nexstar 11" GPS which is very good (around 20 arc seconds without the PEC turned on and roughly 5-10 with it on). Tracking is very smooth and motor vibration is not evident at any magnification.
By now you must have figured out I really like this Synta/Vixen setup. In fact while really love my Celestron Nexstar 11" GPS…I prefer all the additional features of the Vixen over the Nexstar's. Do I have ANY gripes about the modified Synta or Vixen…only a couple of very minor ones. I wish the Synta mounts had the extra few tweaks factory installed. They would have one heck of a great mount. As it is…it can be a great mount but only after some extensive tweaking. I understand the new Synta EQ-6 is supposed to be a super mount and sells for a bit under $1000..but that isn't GOTO so you are looking at some additional bucks to get the same capability. The big Synta is also a huge mount. A Vixen GPD mount without motors will run about $1200. I figure the total "additional" price for the Synta mount when included in a package is probably around $200-$300 not including the motors. You could probably pick up one of these used for very little money and it would be a very cost effective way to get a great mount when combined with the Vixen SS2000PC. As for the Vixen….I have yet to have the computer crash, I haven't detected any glitches in the operating system or database. There are two areas that aren't to my liking. The most serious is the autoguider port. This is not a "standard" configuration (SBIG compatible) so requires some custom cabling even though it is the correct 6 pin RJ 35 port. Evidently it is setup for Vixens own autoguider but I don't believe that it is available over here. That last gripe is really nitpicking. On the very bottom of the hand controller there is a red light that is supposed to be a map light. But it is so faint that it is useless for that purpose. The normal display readout puts out more light.
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