I've got 12" Bintel dob and was thinking for long time to make one of those boxes that can be plugged in computer with astro software, something like home made Argo Navis.
I already read a lot on the net about it. BBartels, Dave Ek box and similar. Getting encoders, where in Australia? I thought it would be OK to get them from Wildcard Innovations 'cos they are around $250 for my Dob. But ArgoNavis computer is $544!! A bit steep considering all hand held ones from Meade, Skywathcher and others are just around $250 the most. Even SkyCommander works out to be cheaper.
So, not to get into why are the pricing too high arguments, I'd like to hear from people who made such a thing. I don't want GoTo (for now), just to make finding things easier by pushing my Dob with laptop or PDA.
I've got 12" Bintel dob and was thinking for long time to make one of those boxes that can be plugged in computer with astro software, something like home made Argo Navis.
bob
I bought a full kit of motors and pre-built circuit board from Bartels a couple of years back and fitted them to a large Dob I then had - with a view to making it a Go-To and tracking Dob. Well, it worked OK even if the slew rate was a bit on the slow side but I found that it was too easy to make a mistake and too unforgiving of mistakes. I blew a circuit board that I had to replace and the chap who bought the scope from me also blew a circuit board in much the same way. It was essential to a Bartels setup that you plug all the cables in before applying power to the system. If you had a bad connection or forgot to plus a cable in to a motor and tried to do it after the device had been started, it seemd to eath out and cook the main IC.
So all in all, my experience with Bartels setup is a bit negative I guess. And in the end it cost a heap more than an Argo Navis.
Back in the early 90's before "goto" telescopes became common I bought a DOB11 driver for my 8" dobsonian. I did not buy all the attachments because I was able to make my own much better. I think the DOB11 is still available!
The DOB11 consisted of a box containg a simple processor and drivers for two stepper motors. When all the parts were fitted the Idea was that you pointed at an object and manually tracked for a few minutes and it would calculate a path and follow this for an hour or so.
The DOB11 can also be connected to a LPT port on a computer and they supplied a basic "BASIC" program to make the telescope into an alt/azm goto telescope. This did kind of work but it was cumbersome and messy to operate. Lap tops were only in their infancy and not a real option.
The main problem with the system was slippage of friction drives and the computer drive sent alternate alt and azm commands every second. Of course once you had the magnification up to about 150 the tracking path was a staircase.
I set about improving the problems. First by making the DOB mount into a stable alt/azm platform with preloaded ball races on all rotating axes. Then designed belt drives to get rid of the slippage, I never completed the azimuth belt drive because I bought a 10" LX200 that made the whole project redundant.
I next wrote a new program to drive the DOB11 (still in BASIC) that gave me a better two star alignment routine, an update every .1 seconds and a hand controller that worked off the games port (awfully slow). This worked but as I said before it was a messy thing to set up at any time and I had just got my LX200 so I stopped all development.
However I did document all the things I did. Particularly the upgrades and I think I still have the drive program.
It was a fun project at the time but not worth the trouble considering the availbilty of simpler commercial goto systems for fork and German equatorial mounts.
Further to this I also experimented with stepper drives salvaged from old MFM HDD's. They were much faster than those from FDD's. I made a controller for the motors and a computer program but never put them on a mount. However they looked good spinning doing an automatic alignment routine and then a psuedo track!
here is an example of the encoder setup/Bartels system that I built from the
ground up. http://www.iceinspace.com.au/forum/s...ad.php?t=42151
This thread, in hindsight, I gave a silly title, not well thought out at
all.
Anyway, it is an improvement in accuracy of the encoder option
that can be added to Mel Bartel's system using old optic mice parts.
I can't speak highly enough of the Bartels stepper drive.
I guess the hardest thing to get would be the encoders. I checked Martins link a while ago with no luck.
Interesting that noone could write a program to connect mice encoders directly to PC and use it that way. I remember reading on the net wiring them with two PC's, one PC with the program reading mice encoders and then that PC connected to second PC with astro software. There must be a way to emulate first PC (laptop) with software.
Interesting that noone could write a program to connect mice encoders directly to PC and use it that way. I remember reading on the net wiring them with two PC's, one PC with the program reading mice encoders and then that PC connected to second PC with astro software. There must be a way to emulate first PC (laptop) with software.
bob
Bob that's where Microcontrollers and stand alone sytems like Gary's
Argo Navis come in.
You need quite a lot of processing power to do it fast and well (Argo)
and an old clunker laptop running DOS to do it adequately (Bartels).
Dave Ek's idea goes down the Micro path.
Many others have too, me included.
Mine's not quite finished yet but is based around a PIC 18F452 micro
with mouse guts quadrature encoders.
Looks like the best solution for me would be EKs box and your mouse encoders. I'd like just cheap ArgoNavis like solution.
I do have 2 stepper motors though. I recently bought Celestron GTL 80 for $100 only. Used it for two nights and than blew it up 'cos of wrong connection, mixed + and -
You wouldn't think that power adopters are wired differently. Center jack should be + but in my case it was not? Blew up hand controller and circuit board on the mount, but motors should be OK.
I am using mouse encoder directly (with mouse driver) on my Bartels.
My encoders are actually the wheels and optical sensors taken from serial mouse, and I am using the chip as well as interface.
However, there are some issues with mouse driver..
Firstly, it should not have acceleration (or it should be disabled), and many have it and it can not be disabled. I tried possibly dozens of them before I found one version which is adequate.
Secondly, the interrupts are not handled properly it seems, so very often program does not update encoder position correctly (when in tracking mode and you move the telescope so it tries to slew back into original position).
David Ek's (or any equivalent) solution is therefore, better because it keeps position in separate micro and sends it on demand to main program.
But, if you are happy with the functionality similar to what Argo Navis is offering, then Mel Bartels program is far, far cheaper than AN.
You can use it without tracking, as Push-To - choose the object from (easily editable) database, push you scope and watch the position of the scope on the screen.
Also, Bartel's system is not for everyone.
It is not for people who do not know how to handle electronic, it is for those who have DIY skills. Noone can blame Mel for frying PC board - you have to know what you are doing and why.
But, this remark actually holds for commercial solutions as well..
Quote:
Originally Posted by bobson
Thanks guys, very interesting experiences.
I guess the hardest thing to get would be the encoders. I checked Martins link a while ago with no luck.
Interesting that noone could write a program to connect mice encoders directly to PC and use it that way. I remember reading on the net wiring them with two PC's, one PC with the program reading mice encoders and then that PC connected to second PC with astro software. There must be a way to emulate first PC (laptop) with software.
I have a Bartels system too and I like it a lot. I plan to add encoders with a David Ek box. I have the Ek box completed. It is not hard to build but I have some electronics minded friends who helped with mine so it was very easy for me.
I have a friend I observe with regularly and he uses the Ek box with Carte du Ciel. He has his laptop attached to his scope with Velcro. You can see the screen display changing as he moves the scope around. It's a very nice system. I use astromist regularly (PDA planetarium). I understand it works well with an Ek box too. I use it with my Bartels system over a bluetooth connection which is very convenient.
I have a Bartels system too and I like it a lot. I plan to add encoders with a David Ek box. I have the Ek box completed. It is not hard to build but I have some electronics minded friends who helped with mine so it was very easy for me.
I have a friend I observe with regularly and he uses the Ek box with Carte du Ciel. He has his laptop attached to his scope with Velcro. You can see the screen display changing as he moves the scope around. It's a very nice system. I use astromist regularly (PDA planetarium). I understand it works well with an Ek box too. I use it with my Bartels system over a bluetooth connection which is very convenient.
Good Luck!
Rod.
Rod,
This is what I don't understand about difference between Bartels and Ek box. Well, I know about Ek box but now I am confused about Bartels
This part:
"I have a Bartels system too and I like it a lot. I plan to add encoders with a David Ek box. "
Am I correct if I say that with Bartels all you could do is tracking the objects with stepper motors, but you can not use it to find things unless you have encoders too?
I hope you don't mind to clear some things for me.
What your friend has is exactly what I want to make.
Bob,
Bartles's system is full blown GoTo or Push-to (if encoders are present) system which can track, find etc object from its data base (and those are just text files, easily editable with any text editor).
The encoders are not necessary for its GoTo operation, though.
You can interface it with Ek's box, or encoders made from serial mouse (with appropriate mouse driver). If you do not have encoders, it will still track and Go-to, but it relies on stepper motor steps counting and if there is a slippage or motors are stalled it will loose the correct position information and you will have to reset it from known object again.
If you do not have motors, and if you have encoders (via Ek's box or mouse interface) you can still use it as Push-to system.
CdC can interface with Ek's box (via ASCOM driver I think, Ek's box is not on the list of standard encoders), so you do not really need Bartels.. (but you will want it some day, I am sure :-)
Bob,
it will still track and Go-to, but it relies on stepper motor steps counting and if there is a slippage or motors are stalled it will loose the correct position information and you will have to reset it from known object again.
Thanks Bojan,
Now its much more clearer. Adding encoders and EK's box to interface encoders makes it more efficient 'cos encoders can't slip but stepper motors can.
Adding stepper motors to Bintel Dob is bigger project than just adding encoders and EK's box.
You are right that I will want GoTo later on, but for now I would be happy with EK's box. It will come handy anyway if I decide to upgrade to GoTo.
Its a bit strange that EK didn't want to make it business and sell it as a self building kit. Like the ones you can get from Dick Smith or Jaycar. This way you buy parts yourself, buy (or make your own) board and chip from FAR Circuits. It would be nice if I could buy all the parts from one place
Thanks again
bob
Geoff,
Thats the best option. Either way I need EK box first.
I found PIC16F84 on Jaycar website but not sure if its the same though. There are couple of different ones and then they need to be programed. Its much cheaper to get a board and chip from FAR Circuit.
Its a bit strange that EK didn't want to make it business and sell it as a self building kit.
Well... not everyone is spoiled with money.
There are a great number of people out there who are happy to just help others... I do not find it strange.
After all, we are amateurs.. actually I even found quite annoying the fact there are some who are trying to cash-in on us and our passion for astronomy.
David will sell you the PCB and all parts (including programmed PIC controller) if you want it for couple of bucks (to cover his expenses)
You are right. What I meant to say is it would be easier to get a kit, it would be cheaper as well for us. Like that digital pulsating kit for dew heater from Jaycar, cost me under $45 bucks all together. Commercial one would cost 10 times more.
You are right. What I meant to say is it would be easier to get a kit, it would be cheaper as well for us. Like that digital pulsating kit for dew heater from Jaycar, cost me under $45 bucks all together. Commercial one would cost 10 times more.
bob
No worries..
You should contact David and ask him, I am sure he still has some kits available.
I am electronics engineer by profession, and I bought the kit from him because I did not have time to source components myself (there are only a few anyway).
Also, the processor needs to be programmed, and this operation is a bit tricky without a PIC programmer at hand.
You should contact David and ask him, I am sure he still has some kits available.
Maybe he was selling them before but now when I go on his website it clearly states he does not sell kits
This is from FAQ from his website:
Quote:
"Can you sell me a complete kit? An assembled unit?
Nope. You gotta collect the parts and build it for yourself. Relax--it's not hard, and you might learn something. If you get stuck, send me an email and I'll do my best to help.
Where do I get the parts?
FAR Circuits sells a printed circuit board and a programmed PIC chip for this project. Go here for ordering details. The rest of the parts can be purchased from nearly any electronics supply house. I use Jameco and Mouser. A parts list with part numbers for Jameco and Mouser is on my how-to-build page."
So, it would be a bit rude to ask him for a kit after reading this.
I found PIC16F84 on Jaycar website but not sure if its the same though.
Yep, same one.
The one Dave uses is the 4Mhz clock version(PIC16F84-04) while the Jaycar one is the newer 'A' revision with 20Mhz clock (PIC16F84A-20).
These differences will not be a problem, as they are backwards compatible, the 20 will run at 4MHz.
