DIY EQ2 Economy Autoguiding

[SteveBz]

OK, so the frac arrived yesterday. It's a Celestron 50 very poor condition but 4.99 + p&p off eBay.   Here it is:

Not only is it in bad nick, but it has been further disabled with (removable) baffles. Nonetheless I stuck a camera in the eyepiece holder and connected to lin_guide.  All systems go, I can see the image in lin_guide but it can't handle HD  guiding so need to step down to some other resolution which I can do with v4l2-ctl.

The issue now is that my ST-4 interface is Arduino so I need to update the lin_guide driver protocol.

Back soon.

Steve.

Edited February 16, 2017 by SteveBz
Size image

[bobro]

14 hours ago, SteveBz said:

OK, so the frac arrived

Great progress Steve obtaining a guidescope and getting Lin_guider to run. Will the Bosma TCE-200 be used as a guide cam? I don't understand your comment 'ST-4 interface is Arduino'. Is the Arduino the receiver for ST-4 signals and controls the (stepper) motors in the mount?

Bob

 

[SteveBz]

6 hours ago, bobro said:

I don't understand your comment 'ST-4 interface is Arduino'. Is the Arduino the receiver for ST-4 signals and controls the (stepper) motors in the mount?

More or less.  I built this:

https://hackaday.io/project/4386-arduino-st4-telescope-control

Which uses an Arduino to steer the mount.  Actually I used it because I built a small radio telescope (see my profile picture) by putting a 1.3 m satellite dish (£5 from eBay, natch) on my EQ5 and I wanted to be able to do a sky-scan with it (built in Python on my laptop).  However, now I've got an Arduino attached to the scope it can be upgraded do all sorts of other things too, eg remote focuser control, dew controller, fan controller, remote shutter controller for DSLR, tell me if it's raining on the scope, pick up the millivolt output of the satellite dish etc etc etc.

Here is the main Arduino hub, the LEDS illuminate with the relevant steering movements:

And if you scroll down the Hackerday article to the comments, there is a link to a lin_guider file on dropbox that someone has modified to link lin_guider to this Arduino control.  I've compiled it in and now it runs.  There are a couple of run-time error messages that I'm just working through, but I hope to be testing guiding with this on the next clear night.

Regards

Steve.

[adder001]

Update. I have got Lin Guider working on the Pi now (PI 3) thanks to your information. I am using a webcam that I got off amazon ages ago that fits into a 1.25 eyepiece for astro viewing. It seems to work and I am planning on connecting this to a small refractor for my guide scope.

However every time it start it says Pulse driver is not initialized, guiding is not possible. I have installed all the packages in the list and the firmware too.

Do you know why I am getting this message and also how do I choose which GPIO pins to have it output signal to.

Thanks in advance for your advice

[bobro]

Looks like you have similar issues to what I found. My workaround was to create a small script to initialise the GPIO pins - run before starting Lin_guider. In addition I modified the program slightly. When I get back from work later today I'll look out the changes I made and let you know adder001. I've found, once running, the program to be very reliable.

You're almost there!

Bob

[adder001]

Thats great, Thanks very much

[SteveBz]

1 hour ago, adder001 said:

Update. I have got Lin Guider working on the Pi now (PI 3) thanks to your information. I am using a webcam that I got off amazon ages ago that fits into a 1.25 eyepiece for astro viewing. It seems to work and I am planning on connecting this to a small refractor for my guide scope.

However every time it start it says Pulse driver is not initialized, guiding is not possible. I have installed all the packages in the list and the firmware too.

Do you know why I am getting this message and also how do I choose which GPIO pins to have it output signal to.

Thanks in advance for your advice

The pulse driver for me was a permissions problem and was resolved temporarily by running as root.  The correct answer is to set up group memberships and rules in er... udev?? which I haven't done yet.

Good luck.

[adder001]

Baaah, I thought I had it. I changed to root and Lin Guider came on with no error messages. Great I thought, then I noticed it had put the camera to NULL. No matter what I set or change it makes me restart LinGuider and then the next session it still shows NULL as camera even though I changed it to webcam.

If I log in as normal and type ./lin_guider then it sees my webcam and I get images shown on the screen but I also get the Pulse driver error message.

This is so weird its as if when logged in as root it cant read the usb port or something

BTW the way I changed to root was

sudo chown root lin_guider
sudo chmod +s lin_guider

which seemed to work

I also tried another way using sudo su to make me a superuser and it also displays root in the prompt area when I do this.

Very strange, Im puzzled now

[bobro]

Here is a link to the small mods I made to get Lin_guider to run for me. Note that I know little about Linux or the Raspberry PI, so treat the mod as a bit of a bodge. See the notes file for an explanation. Let me know how it goes.

http://guidingfiles.web.fastmail.co.uk/

[SteveBz]

Did you see this?  He's coded the whole thing from scratch in Python:

http://sy2000.blogspot.co.uk/2014/05/star-autoguide-with-rpi-5-python-code.html

I've run it and it works (although I don't have an RPi).  I'm trying to hack it for my Arduino.

Regards

Steve

[adder001]

On 18/02/2017 at 17:48, bobro said:

Here is a link to the small mods I made to get Lin_guider to run for me. Note that I know little about Linux or the Raspberry PI, so treat the mod as a bit of a bodge. See the notes file for an explanation. Let me know how it goes.

http://guidingfiles.web.fastmail.co.uk/

Many thanks for your information thats very helpful, I really appreciate it. I am so close, The problem is definitely with Lin Guider somewhere as no matter what I do I still get the guiding error.

I decided to go right back to the beginning with a fresh install of raspbian, then reinstalled lin guider then the firmware did all the sudo apt-get updates, ugrades etc.

Ran as root, still no joy. The camera works fine though, just still no guiding. I even copied and pasted the modified code into my io cpp file, still no joy.

I know that the GPIO's are working because if I use wiring Pi and talk directly through terminal to the GPIO pins or use Python to make a small GPIO blink programme I can get a test LED to light or switch on or off depending on what I programme it to do.

Also the guider script works on its own as well (if i modify it I can make the LED connected on GPIO 22 switch on or off)

So this is a real puzzle now

[adder001]

5 hours ago, SteveBz said:

Did you see this?  He's coded the whole thing from scratch in Python:

http://sy2000.blogspot.co.uk/2014/05/star-autoguide-with-rpi-5-python-code.html

I've run it and it works (although I don't have an RPi).  I'm trying to hack it for my Arduino.

Regards

Steve

Cheers, thats interesting I will have a look at that, Thanks

[bobro]

32 minutes ago, adder001 said:

So this is a real puzzle now

If I don't run the 'Guider' script file before starting Lin_guider I get the same error message about the pulse driver. Are you running the script first? It can be run in Terminal mode to see the output. My Lin_guider version is V4.1.0.

[adder001]

yeah I run it first, followed by lin guider. But something interesting is happening where I have to modify the text in the file from high to 1 or it just errors.

I wrote my own script just to confirm that it works and my version only seems to work if I use digits rather than words eg., 1 instead of high. This was tested by connecting an LED to GPIO 22

[adder001]

Just check and mine is 4.1.1 so there may be some slight differences here, I am going to try and install the older version

[bobro]

I suspect the issue is down to the (very confusing) PI GPIO pinout between revisions. If you still have a problem after trying 4.1.0, I suggest asking a question in another part of this forum. Someone is bound to know!

[adder001]

Yeah it is very odd the various options and layouts when it comes to the Gpio configurations. Thanks again for all your advice. If I get anywhere with this I will post more info. Cheers

[eyedeekay]

I really like your project and progress. I am actually doing something similar, but with the use of an eq1 mount. I had the economy drive as well but I opted toward using a separate stepper motor that accepts microstepping. If your interested, here is my project currently:

 

 http://www.astronomyforum.net/atm-diy-telescope-making-forum/230117-eq1-ra-only-autoguider.html

 

I also have the forum post that gave me the arduino coding if its any use for you:

 

https://forum.arduino.cc/index.php?topic=245679.0

[bobro]

Thanks for the info on your excellent project. Coincidentally, I've just ordered an Arduino Nano to allow my mount tracking to be driven by PHD2. The Arduino to be loaded with Kevin Ferrare's code https://github.com/kevinferrare/arduino-st4/ and a modified relay board to interface to the motors.

With APT loaded on the PC it should make for an integrated imaging and guiding system - if my eeebook is powerful enough to drive everything!

Use of a stepper motor may give better tracking (less jitter) than the simple DC motor used in the Economy Motor Drive, though I find the biggest sources of trailing in my setup are the wind and accuracy of polar aligment (with longer exposures).

Good luck with your project - I look forward to seeing some images!

 

Edited February 21, 2017 by bobro
spelling

[eyedeekay]

13 hours ago, bobro said:

Thanks for the info on your excellent project. Coincidentally, I've just ordered an Arduino Nano to allow my mount tracking to be driven by PHD2. The Arduino to be loaded with Kevin Ferrare's code https://github.com/kevinferrare/arduino-st4/ and a modified relay board to interface to the motors.

With APT loaded on the PC it should make for an integrated imaging and guiding system - if my eeebook is powerful enough to drive everything!

Use of a stepper motor may give better tracking (less jitter) than the simple DC motor used in the Economy Motor Drive, though I find the biggest sources of trailing in my setup are the wind and accuracy of polar aligment (with longer exposures).

Good luck with your project - I look forward to seeing some images!

 

Thank you so much! Like you wind and polar alignment always kill me when I'm trying to track. Since im ra guiding only my dec has to be really precise, and wind confuses phd2 while tracking. I plan to step down my telescope size from the included 114mm 900mm scope to a small wide field refractor, it will be so much more manageable. 

Good luck with your project too!

[adder001]

On 19/02/2017 at 13:37, SteveBz said:

Did you see this?  He's coded the whole thing from scratch in Python:

http://sy2000.blogspot.co.uk/2014/05/star-autoguide-with-rpi-5-python-code.html

I've run it and it works (although I don't have an RPi).  I'm trying to hack it for my Arduino.

Regards

Steve

Finally gave up on Lin-Guider, I feel that I tried everything. Its like I am just trying to push water uphill, different installs raspbian o/s, Linguider versions and different firmware still no joy. Don't understand what I am doing wrong. I have followed lots of of different setup/installation instructions that people have said they have had it working but still not for me. This programme written in python however appears to work, I get a good camera view and signals to the GPIO although I have only used an LED on the pins at the moment but at least that shows that it is doing something so I thinh that I will go with this for now.

So many thanks for all the advise and I will post any developments that I have

[SteveBz]

9 hours ago, adder001 said:

Finally gave up on Lin-Guider, I feel that I tried everything. Its like I am just trying to push water uphill, different installs raspbian o/s, Linguider versions and different firmware still no joy. Don't understand what I am doing wrong. I have followed lots of of different setup/installation instructions that people have said they have had it working but still not for me. This programme written in python however appears to work, I get a good camera view and signals to the GPIO although I have only used an LED on the pins at the moment but at least that shows that it is doing something so I thinh that I will go with this for now.

So many thanks for all the advise and I will post any developments that I have

Yes, I gave up on lin_guide too. Mainly because of my non-standard  (arduino) mount. I'm customising the python code above. If I ever get it working, I'll post it. Luckily the weather is so bad that there is no urgency for it.?

Steve.

[SteveBz]

Hi Guys,

Well I got outside briefly with the scope and guide (see earlier post) last night.  I don't have any guide-scope rings yet, so choosing a star was a bit hard, however there were lots of bugs, so I took a screen dump of a star through the guidescope, saved it as a test star and went inside to debug.  I should say it's all based on the fantastic work done by Maple Yang here:

http://sy2000.blogspot.co.uk/2014/05/star-autoguide-with-rpi-5-python-code.html

Some of the bugs are cleared up and here are a couple of screen dumps of the program:

Tracking (simulation):

However, I'm not sure how big corrections need to be adequate to fix tracking errors, but not too great to cause oversteer.  Does anyone have any idea of the magnitude of movement that corrections should try to be?  If I have my handset set to Earth-speed or twice Earth-speed, should I shoot 1 second pulses at the motors or millisecond, or multiple second corrections?

What do people think?

Regards

Steve.

Edited February 25, 2017 by SteveBz
Adding references

[bobro]

Congratulations Steve on getting this far with guiding. It's very likely that many will be using PHD for guiding. If you haven't seen it, here is a link to a PHD tutorial: 

As I use Lin_guider I can give you an overview of how I 'tuned' it for my setup by trial and error setting of the guide parameters. The setup is unusual in its use of DC motors rather than stepper motors, so it will likely respond in a different way to a stepper motor system. Nevertheless, the basic principles should still hold.

Following Lin_ guider calibration, guiding was started on a star chosen by Lin_guider. The guiding graph shows the error in guiding and, of course, the aim is to make this as small as possible and correct guiding errors as quickly as possible. If the Python guiding program doesn't produce a graph it may be possible to observe the central star to see how guiding is performing.

Proportional Gain setting (RA Aggressiveness) - this is set to a value that corrects a largish error with some dampened oscillation about the mid-line. If this value is too high oscillations may grow and guiding will fail. If this value is too small (no dampened oscillation) it will take too long to correct an error. Set to 10 for my setup.

Integral setting (RA Hysteresis) - if guiding continually swings backwards and forwards, this can be reduced by adding together calculated guiding corrections, so smoothing out the calculated guide error. I didn't use this setting as stability wasn't an issue.

Minimum correction - this helps to stop tiny corrections that may not be useful (guiding noise). In my setup  a value of 50msec still seemed to provide useful correction. 

Maximum correction - large guiding corrections shouldn't be necessary, though may be calculated due to wind on the mount. Limiting the maximum correction helps stop sending the scope too far off course (it should come back as the wind effect disappears). 500msec is a good starting value for this.

DEC settings - luckily my setup doesn't suffer from DEC backlash, so I was able to tune the DEC parameters in the same way, with final values being not too different to RA. If backlash is an issue it may be better to guide DEC in only one direction.

One area I don't really understand with Lin_guider is the frequency of guiding. I think it may be down to the webcam I use which doesn't support long exposures. The result seems to be that Lin_guider can issue multiple (perhaps 5 or 6) guiding corrections each second. This is perhaps a good thing as it helps with a fast guiding response. 

Hope the above is useful to you and good luck with 'tuning' your setup.

Bob

[SteveBz]

1 hour ago, bobro said:

Proportional Gain setting (RA Aggressiveness) - this is set to a value that corrects a largish error with some dampened oscillation about the mid-line. If this value is too high oscillations may grow and guiding will fail. If this value is too small (no dampened oscillation) it will take too long to correct an error. Set to 10 for my setup.

So, I think the quick and easy thing to do is add this field to my input screen for both Dec and RA and then do the others if I need to. 

Thanks very much.

Steve.