Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_30_second_exp_2_winners.thumb.jpg.b5430b40547c40d344fd4493776ab99f.jpg

tekkydave

Arduino Ascom focuser Mark2

Recommended Posts

I'm hooked on this thread and now want to build it but I've a few questions.

1. The stepper motor used has a 5.6deg step which gives 64 per rev if I'm not wrong. Would it not be better to use a finer motor?

2. If I swapped out for a 12v stepper could I power it with a mains adapter without frying the nano?

Thanks for any feedback

Campbell

1. You can use any stepper that suits your project. I chose the one I did because it was cheap :grin:

2. You can feed 7 to 12v into the Vin pin (pin30)

Share this post


Link to post
Share on other sites

This stepper has a built in 64:1 gearbox.  I've used several for focussing and found them very good :)

Edited by Gina

Share this post


Link to post
Share on other sites

I've only got that standard stock focuser for my 200p, I've noticed most here seem to be using dual speed.

I'm aiming it would be best to use this in the dual speed focuser?

Share this post


Link to post
Share on other sites

I have a single speed Crayford focuser on my MN190 and using a 5:1 ratio timing pulley system.  I removed the knob and put a 60t MXL timing pulley on the shaft with a 12t pulley on the 28BYJ-48 stepper motor.  I found the step size quite small enough for accurate focussing :)

  • Like 1

Share this post


Link to post
Share on other sites

I've only got that standard stock focuser for my 200p, I've noticed most here seem to be using dual speed.

I'm aiming it would be best to use this in the dual speed focuser?

You can calculate critical focus zone with this link.

http://www.wilmslowastro.com/software/formulae.htm

My scope is ~150um, so I have to go with 400 steps (40um/step) if I have to use coarse knob.

Share this post


Link to post
Share on other sites

Not in normal use as it is on Windows. Ascom is windows-only software. I have noticed it when using the nano on Linux for other projects but you just get a few random characters then it settles down.

so it is still working properly?

Share this post


Link to post
Share on other sites

so it is still working properly?

Yes it works fine. As the arduino site says if you are using the serial port in your program you need to make sure you put a short delay in your program before doing any comms. You will only ever use the focuser on Windows so its not an issue for that.

  • Like 1

Share this post


Link to post
Share on other sites

I'm assuming I would be have to buy the "big Easy stepper driver" for my motor if it didn't have the small driver board as the one used in this thread? .

Would of the rest of the instructions still be applicable?

Thanks

Edited by sulaco

Share this post


Link to post
Share on other sites

I'm assuming I would be have to buy the "big Easy stepper driver" for my motor if it didn't have the small driver board as the one used in this thread? .

Would of the rest of the instructions still be applicable?

Thanks

No reason why you couldn't use that board but you would need to modify the clockwise() and anticlockwise() functions in my sketch as it uses direction/step signals instead of 4 separate data lines.

Share this post


Link to post
Share on other sites

Yes it works fine. As the arduino site says if you are using the serial port in your program you need to make sure you put a short delay in your program before doing any comms. You will only ever use the focuser on Windows so its not an issue for that.

Good. I thought the board will be reset every time there is a COM communication, eg, every time ASCOM driver is sending a command to the motor. I am thinking if it is possible to mimic another motorized focuser so that we can reuse the app.

Share this post


Link to post
Share on other sites

Good. I thought the board will be reset every time there is a COM communication, eg, every time ASCOM driver is sending a command to the motor. I am thinking if it is possible to mimic another motorized focuser so that we can reuse the app.

By 'app' do you mean the sketch, client program or driver? Any focuser client that uses ascom should work with my focuser if you use my driver.. The device-dependant coding is in the driver. If you want to use the driver of another focuser you will need to find out what the comms protocol/commands are and rewrite the arduino sketch to work with it. I designed my own protocol in this case because I wanted to learn about both parts. I believe someone on SGL has made an arduino-based focuser that uses the Moonlight protocol & driver but I can't remember who it was.

Edited by tekkydave

Share this post


Link to post
Share on other sites

You can calculate critical focus zone with this link.

http://www.wilmslowastro.com/software/formulae.htm

My scope is ~150um, so I have to go with 400 steps (40um/step) if I have to use coarse knob.

Don't forget the advantage in the pulley system. Mine is 4:1, so 1 revolution of the coarse focus knob = 256 steps. You could easily make it 5:1, 320 steps.

When I made mine I had doubts on whether the motor's steps were fine enough but it was so cheap I figured it would be worth a go and maybe upgrade later. As it turns out it is more than adequate, I doubt that the movement would be quantifiable if it was much finer.

Edited by wuthton
  • Like 1

Share this post


Link to post
Share on other sites

Cheap! How very dare you. Inexpensive please :grin:

My sincere apologies, I meant cost effective.

  • Like 1

Share this post


Link to post
Share on other sites

By 'app' do you mean the sketch, client program or driver? Any focuser client that uses ascom should work with my focuser if you use my driver.. The device-dependant coding is in the driver. If you want to use the driver of another focuser you will need to find out what the comms protocol/commands are and rewrite the arduino sketch to work with it. I designed my own protocol in this case because I wanted to learn about both parts. I believe someone on SGL has made an arduino-based focuser that uses the Moonlight protocol & driver but I can't remember who it was.

Yes. I was thinking if it can be used under mac osx. I plan to  migrate everything to mac, for me the only thing mac osx does not support is ASCOM.

Share this post


Link to post
Share on other sites

Don't forget the advantage in the pulley system. Mine is 4:1, so 1 revolution of the coarse focus knob = 256 steps. You could easily make it 5:1, 320 steps.

When I made mine I had doubts on whether the motor's steps were fine enough but it was so cheap I figured it would be worth a go and maybe upgrade later. As it turns out it is more than adequate, I doubt that the movement would be quantifiable if it was much finer.

http://www.astrodon.com/Orphan/parfocal_and_critical_focus_zone/

Based on above experiment, step size is definitely critical for the imaging system, that is why I am more concern about step size. I also plan to use the same system for a much faster scope, which demands even finer step.

Share this post


Link to post
Share on other sites

Yes. I was thinking if it can be used under mac osx. I plan to  migrate everything to mac, for me the only thing mac osx does not support is ASCOM.

Sounds interesting. I have no experience of Macs. What client program do you plan to use and how will it interface to the arduino?

Share this post


Link to post
Share on other sites

"USB device not recognised"

Started getting this message a week ago, and solution was to unplug the focuser from the USB hub and plug it back in. Now that's not working and get this message every time I plug the hub (powered) into the laptop. 

I've tried plugging the focuser directly to the laptop and it's recognised and works, so seems the device is OK.

Anyone else come across this error? Maybe I need a better quality hub?

Share this post


Link to post
Share on other sites

Often - yes :(  I hate USB!  I get it a lot with Arduino Nanos for some unknown reason :(

Edited by Gina

Share this post


Link to post
Share on other sites

Often - yes :(  I hate USB!  I get it a lot with Arduino Nanos for some unknown reason :(

It seems to be working again. I might try adding a separate power source, PP9 battery, and see if that helps with stability.

Share this post


Link to post
Share on other sites

"USB device not recognised"

Started getting this message a week ago, and solution was to unplug the focuser from the USB hub and plug it back in. Now that's not working and get this message every time I plug the hub (powered) into the laptop. 

I've tried plugging the focuser directly to the laptop and it's recognised and works, so seems the device is OK.

Anyone else come across this error? Maybe I need a better quality hub?

Is it a powered hub? Do you have anything else connected and is it ok if the focuser is the only device?

Share this post


Link to post
Share on other sites

Hello all :D

I bit the bullet and built the focuser as well! There will be pictures of course :-)

So I wanted to thanks each and everyone for contributing on this thread. Special props for the ASCOM driver to tekkydave.

I' m using a NEMA17 motor and have modified the source code per suggestion.

On the bench it looks like working successfully but on accuracy will need to look on the field to be sure! The gear speeds must be a messed mixed up since i got the gears suggested on SF with a 400step motor :-)

I do have a question though : 

When we initialize the focuser, must it be ,already,  on a very close to focus position?

And do I need to adjust that initial position number in the ascom popup or it doesn't matter that much?

  • Like 1

Share this post


Link to post
Share on other sites

Hello all :D

I bit the bullet and built the focuser as well! There will be pictures of course :-)

So I wanted to thanks each and everyone for contributing on this thread. Special props for the ASCOM driver to tekkydave.

I' m using a NEMA17 motor and have modified the source code per suggestion.

On the bench it looks like working successfully but on accuracy will need to look on the field to be sure! The gear speeds must be a messed mixed up since i got the gears suggested on SF with a 400step motor :-)

I do have a question though : 

When we initialize the focuser, must it be ,already,  on a very close to focus position?

And do I need to adjust that initial position number in the ascom popup or it doesn't matter that much?

Thanks for your comments, I am truly inspired by the number of people who have used my project.

It will probably help if you are near correct focus to start with. I am working on a new version that will remember the position of the focuser even when it is powered down and it will start again from that position unless overridden. I haven't really used mine for any imaging yet as I have been concentrating on building my pier and obsy/shed when I get my little free time.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.