Mel Bartel/Dan Gray Servo Goto Systems

[netwolf]

Hi All,

Would like to here from other users of the Bartel Servo setup, particularly those using Dan Gray's Sitech controller. Mel originally wrote the ScopeII java software to control PicServo controllers using the PicServo protocol. Dan later came up with the Sitech System that can emulate the PicServo controllers. This is very similar to the ServoCat system. Dan has now created his own Ascom driver so ScopeII is no longer required to controll the controller. The Ascom Driver now does this for you. And in the latest firmware PEC is now onboard the controller. The controller can be used once configured via a PC, to work in standalone mode to provide Slew and Track functionality. It can also be used in conjunction with Argo Navis or Sky Commander DSC's to provide full stand alone goto without the need for a PC.

More information here.
http://siderealtechnology.com/
and here
http://tech.groups.yahoo.com/group/SiTechservo/

The great thing about the Sitech controller is that it can with the right firmware be also used to control Stepper motors. Dan is currently only providing firmware for Servo use and is developing a third generation controller that will permit use of Direct Drive motors as well as Servo's and Steppers.

I am in the process of making my G-11 goto using this controller. I have opted to source and use the Gemini Goto Servo motors, as these bold on to the Mount of the shelf. Others like Chuck Shaw (the Sitechservo yahoo group creator and moderator) and others have adapted the Pitmman servo motors to the G-11 mount. Chuck has put some files in the Sitechservo group's file section on his method and has promised to provide a inventory of parts soon.

I would really like to hear from other users of this system and compare notes on how they have done it. Bojan has already got a thread on the Stepper system so I would like to keep this one about the Servo setups.

I am also interested in hearing from people who have actually combined the AN or Skycommnader DSC with this controller. How well does this setup work in standalone mode. Can the AN features like TPAS etc be used to there full pottential with this setup. The Sitech offers PointXP in the Ascom driver, but in standalone mode it would really on the AN. So I would like to know how well this works. I guess here we may have to open up the discussion to people with ServoCat systems as that is the more widely used combination with the AN.


Regards
Fahim

[tnott]

Hi Netwolf,

Not seen any of the Sitech systems in use sorry but know that the Spica Eyes telescopes use it. Chose the Servocat Junior system because of the small gearboxes. The Servocat system is well-tested and ready to go out of the box. The Sitech is a bit more atm-involved I think but still compatible with Argo Navis. Also, you need to provide your own mechanical drive system whereas it comes included with the Servocat.

[netwolf]

Tim, what do you mean by mechanical drive? Dan does offer Gear and Clutch or Worm Gear assemblies. Even with a ServoCat you do need to do a bit of ATM to fit the drive onto your scope. Agreed that the Servocat is the more mature product of the two and is more well known. Tim are you using yours with the AN? How do you find this combo? From what I have read its the best you can get.

[tnott]

What I mean is the actual thing that is connected to each axis to make it move. The Servocat has a spring-loaded knurled wheel that presses into the wood of the ground ring on the Az. and cable drive on the Alt. The Servocat comes with very detailed instructions, DVD, CD-rom, photos, templates and all the hardware you need in individual packages so even a complete fool (like me) can install it in a few hours. Most people who buy it are not ATMers.

The software is easy to use and you it also has has an auto calibration function, whereby the precise gear ratios and backlash can be computed automatically. Also has slip return, spiral search and local area sync functions.

Of course, this is provided it is a fairly standard dob design. If it is something else (like mine) it will take a bit more fiddling around.

When I enquired, the Sitech system did offer clutch/gearbox assemblies but how you get it to actually drive each axis (friction, timing belts, worm gears,) is up to you to figure out. I do like the idea of the slip clutches though. On Servocat you have to dis-engage a lever on each axis to go manual.

http://hbanich.googlepages.com/
http://www.equatorialplatforms.com/spica.eyes.slipstream.html
http://www.siderealtechnology.com/28inch/

BTW - The Argo/Servocat combo works very well together - any bugs have had plenty of time to get worked out.

[DavidH]

Hi Fahim,

I have been following your G-11 upgrade with some interest. I intend doing the same with an AP900qmd. Currently, I am running an Argo Navis/ SiTech servo controller combination on my home built 200mm dob. I can report that the combination works well, and can see no problem converting to an equatorial setup. I have installed a separate "GoTo" button on the top of the handpad, so that I don't have to press both buttons to initiate a goto. There were a couple of northern hemispherisms to be overcome when I first used the SiTech controller, but Dan Gray was really helpful and we sorted them out PDQ. I am happy to compare notes if you think it may help.

Regards,
David.

[netwolf]

Tim, I understand what you mean and you are right there is more to get than what is offered. But you could source from Lenord at http://www.gototelescopes.com/servocontroller.htm
He is also an active member on the Yahoo Sitechservo group.
He has done various conversions of Alt/Az and EQ mounts and usually has all you need to get a complete bolt on solution.
But yes Servocat being a more mature products is out of the box ready to go for most typical installations.


David, are there Servo motors available for this. On there website the mention due to other issues upgrades are not available. I have not seen a AP900 conversion to Sitech yet, so you may well be the first to do it. As such you will need to get Servo motors and figure out a way to mount them to your Drive system. Try posting on the yahoo group to see if anyone has done or seen a conversion like this. I am not very good with making things so i just bouhgt the Gemini servo motors, so i can have a bolt on solution. If you can do it yourself then then that is well and good. If not you could also speak with Lenord to see if he has done a AP900 conversion and if he can offer an adapter for you.
Also would not hurt to ask AP to see if the can provide you with the Servo Motors etc.

Regards
Fahim

[DavidH]

Fahim,

There is no conversion kit available from AP for the QMD mounts. They say that the QMD mounts with steppers were not of sufficient precision to give accurate goto when converted to servo drives. I can't comment on whether this is true or not, but I have achieved quite good goto with my wooden dob built in the garage, and if I can't do better with an AP mount as a starting point I'll be very disappointed. Maybe my standards for accurate goto capability are not quite as high as AP's ;)

I will not be making any irreversible changes to the mount, so I can always go back to the extremely accurate tracking available with the steppers if the servos don't work out.

At the moment, I have had a friend machine up a couple of shaft extensions to mount some toothed pulleys on the end of the worms, and still have to make a couple of mounting plates for the motors. I am in the process of shifting house at the moment, so the project is on the back burner. Will let you know how it pans out.

Regards,
David.

[netwolf]

David, I am glad to here from another Sitech user. I also just read there notice about upgrades. But I think this is very sad let down for many who have invested lot of money in the AP name. The same thing happned with my mate he bought the Losmandy GM-200 and just a month later they released the HGM-200 but would not offere a upgrade to the tangent arm on the GM-200. The HGM and GM are identical and only the DEC axis is different, you should be abele to just get a HGM DEC assembly and use it on the GM-200. My mate has tried very hard and no luck. Given the amount people invest in these high end mounts, you would think that an upgrade path would be made available to you. I think you can get good results with the Sitech and the AP900.

Regards
Fahim

[DavidH]

Thanks Fahim,

But there is no need to be upset on my account. I bought the mount second hand knowing its capabilities(or lack of them) and potential. It is a superb mount, goto or not. It comes standard with 4192 count encoders, but can easily be upgraded to 10000 step encoders for greater push to accuracy. I have checked the PE of the mount and found it to be around +- 4 arc sec. The general mechanics of the mount are a pleasure to use when compared to my GM-8(stepper version). The only thing I miss about the GM-8 is the azimuth adjustment when polar aligning. The Losmandy system is better.

Regards,
David.

[netwolf]

David, +/- 4 wow that's very very good, is that with our without PEC.