I am trying to set implement a Bartels stepper system on my 12 inch F5 newt. I have the electronics and have modified my dob mount (a flex rocker for a 12 inch F5). I can't decide on the best reduction system but I am leaning towards epoxy gears because becuse my machine skills and equipment are limited. I would love to correspond with anyone doing a similar project. I am in Mt Martha on the Mornington Peninsula.
Hi Rod,
so it seems there are two of us :-)
My reduction is made of two worm gears (1/180) that I found in the misc bin in my friend's machine shop.. He found them on some other waste and decided he should store them for a while :-)
Also, the telescope's hor wheel rides on the 12mm shaft, driven with the worm gear..
I have seen a lot of epoxy gear solutions on the web and this is something I would have adopted if I had not have this solution.
Just be careful how the whole thing is put together, you will want to have the same portability as it was before bartelization.
Apart from couple of hickups with the software ( I have some funny issues with encoders, but I managed to circumvent the problem, partly with the help from yahoo group and Mel himself), the system works great, and it does not cost heaps of dollars, like some commercial systems out there, the price/performance ratio is excellent.
Good luck with your project :-) I would be very glad to assist, if you need any help :-)
I do have a question at this point. It sounds like you used friction rollers to drive the scope. Did you have any problems with microslippage? Or did the encoders fix that? It's the reports of microslippage that put me off the roller system but if encoders fix it, I would seriously consider it.
I do not have a problem with any kind of slippage, but on the other hand, all depends on what you want out of the system.
For up to one hour of tracking and visual, there are no problems. System accepts commands from guider, so that should correct the possible problem 100%.
Since I do not have permanently mounted telescope, whenever I use it I just level it and then point to a known star and reset its coordinates, this is good enough for majority of my purposes at the moment.
For GOTO I had some problems in the past with slippage in the azimuth butthis was because of the design specifics (I am using a roller reduction and at the beginning there was not enough pressure in one direction. I believe I sorted this out with different design approach.
I never noticed any problems on altitude axis, where the telescope rides on the axis with its full weight.
BTW, I know for sure that many professional instruments are using friction roller reduction, it is cheap and there are no periodic error, inherent to gears.
Encoders should correct for slippage, however this will depend on their resolution.. and this is an area where I have some problems (oveshooting when telescope is returning to the correct position when encoders indicate the slippage, and that problem seems to be specific to my system only, since nobody in the bartels community knows what is the cause and cure).
Nevertheless, I am using encoders only as an input to a new position, when I want to observe something on the other direction during starparties (without encoders, I should either slew to the new position with motors which takes a long time - or I should stop tracking, then point to the new object, then I find that object in the data base, then reset to the new coordinates - all this takes a long time as well).
The easiest way to hop to a new object is the same as with conventional dobson: just stop tracking, push the scope to a new direction (encoders are updated every second automatically) and when there, start tracking again. GOTO function I am using for close objects within couple of degrees, and only when I am looking for them because I do not know exactly where they are.
As far as field rotation is concerned, I have not implemented it yet, but it is in my plans for the near future (when I get my Canon 400D).
So far I was using B/W Quickcam for shots up to 30 secs focally, with tracking and no guiding, and there were no problems observed :-)
Afocal avi's with my Kyocera were also OK :-) I had bigger problems with atmospheric turbulence and vibration (after touching something) than with tracking.
To give you a better idea of tracking accuracy, attached here is 10s prime focus shot of trapezium....
It is not a great image really, mainly because it was very windy and the seeing was terrible ... but it indicates that the tracking was OK during that time.
I think I posted on the forum before the longer exposure of Proxima (20 ~ 30sec), no traces are visible on it either.
Actually, in Newtonian telescope case, the prime focus is where it would have been if there were no secondary mirror.. so you are right to the certain degree (you missed by the radius of the tube..).
But since the secondary mirror does not change the optical properties of the system (apart from moving the focus point outside the tube and flipping sides of the image) , Mike is also right :-)
So, both of you are right if we assume we are talking about Newtonians :-)
And, if we want to be really correct in naming things here, this should be called "Newtonian focus"...
Hi Bojan,
I just saw your original (2 years ago) post. I'll add myself to the list of the Bartelised.
I'm in the process of a grand refurbishment of a 16" Dob I bought last year - OK, so I'm slow - and would be grateful to be able to share some experiences and solutions with others who have done a Bartels implementation.
The mount for this scope is a heavy blighter, made from 2" box section sleel and steel plate. I'll attach a few photos.
The key to it is in the drives of course. The base of the mount has 3 wheels to which I have added a screw-down levelling system and a bearing or two. It is pullable but without dissasembly, an absolute beast to move anywhere far from home.
The Alt bearing is identical to the Az and is mounted on one arm of a yoke - with a slave shaft and bearing on the other side. I had a hell of a time getting all these to run true because the mount - while solidly built, was out of whack in several directions.
The drives in both Alt and Az are 200-step steppers run into a 25:1 reduction box and then through a worm drive to a 180-tooth gear driving a shaft on which the scope turns. My maths says this gives a 1.44 arc/second per step. But I am suffering major brain-fade when it comes to the software controlling these motors.
I bough a ready-made board from Mel (with the motors also) and although it has a field rotation capability as well as focus control, I don't use either yet - there isn't much point in getting the focus right if the thing can't track and slew.
So may I ask if anyone has been through the process of working out the Config.dat file for the Bartels software and is still sane.
Hi Pmrid
Welcome to the club (of bartelized scopes)
Your machine looks great!
As far as config.dat is concerned, we (Rod and myself) are still sane and sound.. and the thing even tracks !
I also do not use field rotation (this is only for photography anyway and I am using mine for visual at the moment.... for photography I will mount my newtonian on Bartelized EQ6 one day).
Focus control via PC is also somewhat too much of an overkill... but with the rest of the settings there were not so many troubles.
And I never bothered to fine tune microsteps, as I found the major source of un-smoothness of the motor rotation comes from the fact that the PC I am using has 100MHz processor (it should be at least 200MHz or over).
Thanks for the reply. The problem I have with the motors/drive system on both axes is that when I use the handpad to slew, or use the Scope program to do the same thing, the motor seems to accelerate up to a point (quite quickly - only a second or two) when it makes sort of rattling noise and doesn't seem to have any torque. It isn't a problem with the gears or whatever, they are now well balanced and run freely and smoothly. It is in the way Scope the software is controlling the motors.
Did you have to make many changes to the Config.dat file to get your system operating?
Your MinDelay is probably too short, this controls the max speed of the motor. If the max speed is set too high, the motors can not cope and they will stall (as they apparently do) .
set this var to higher value (until the motors run OK on maximum speed).
Also, you can try to change the HsRampX, set it to 1 (as above), this will result in lower acceleration.
Also, check the power supply voltage, maybe it is too low?
Yes, I have to have some changes, mainly in above area, then to adjust the gear ratio (AltFullStepSizeArcsec and AzFullStepSizeArcsec).
Also I needed to adjust microstep parameters (I am using 24V and my motors are 15V or so) to lower the motor current. But this was done later it was not essential, like HS parameters.
I have had this sort of a problem. I found it to be a loose connection to the stepper motor or a crossed wire.
I didn't find adjusting msconfig too difficult to get slews happening. I just entered rather large numbers in mindelay (over 800) and maxdelay (over 2000) and gradually reduced them to the point where the motors stalled and then just incresed them slightly (to stop the stalling). Slews are a little slow on mine - just under 2 degrees per second.
Hi Rod, and many thanks. I'll report back. But for now have to go earn a living (darn it but it does interfere with the good stuff doesn't it?). I'll be offshore now until mid-July. But I'll resume the challenge then.
cheers and thanks again.
Amusing the way fate steps in and solves problems for you. I just managed to cook the circuit board on my Bartels stepper controller system - not entirely sure how I managed that but for now, the scope can go back to sleep while I cool off a bit.
Peter
