DIY - Budget Autofocus for Newtonian / 130PDS

[FrenchyArnaud]

Hi guys, so, following the thread here : 

 

I decided to undertake the build of a DIY electronique focuser. I could of course, buy a zwo eaf or equivallent but that's just too expensive (no offense to @FLO )
DISCLAIMER : I know NOTHING about electronics. I know quite a little bit about programing C and other languages - but as it turns out, contrary to my intuitition, there is absolutely no need to. 

So, after a lot of reading and studying, I settle on an arduino based system and specifically, "myFocuserPro2", a very complete project that you can find here. 

I bought all the parts off of amazon and ebay. That's a little elegoo kit with cables and breadboard (£12), and arduino UNO Rev3 (£10), a stepper motor + associated driver board (28BYJ-48 & ULN2003, £6) and a Step-Down Power Supply Converter Module 12V to 5V (£3). It was not needed but just for fun I also bought another Arduino, a nano (for the permanent assembly when my prototype is ready to deploy) 

The total is therefore about £30, and I will need a few mechanical bits and bolts for the linkage - it will all be well below £50. 

Having never done any sort of electronic assembly, and having read an awful lot about the topic, I was expecting a very tedious and complex process. In actual fact, it took me about one hour, download of software included, to get a working prototype that is 100% integrated to NINA. 

I must point out at this stage that I am in fact building the most basic version of myFocuserPro2, with no probe, display, buttons - nothing. My plan is to have everything piloted from the computer and the linkage will be pulley and belt. So, I just stupidly copied the connexions explained (no need to understand what does what, just imitate the plans supplied) and upload the firmware (so easy it's stupid and no need to even look at the content, let alone edit the code), then copy-paste the libraries were they belong (it is essential but dead easy and very well documented) and download the ascom driver (supplied too, nothing to think about, just grab and install.) Anyways, after less than an hour, without knowing anything and for pocket money, I have my autofocuser 100% integrated to NINA ! 

 

So, the rest of the project will be to

1) replace the arduino UNO by the nano and confirm it all works as intended
2) encase the electronics and lengthen the connexion between circuit board and motor
3) Link mechanically the motor to the focuser of the 130PDS (which involves building a metal bracket and installing a GT2 pulley and belt)

Pretty chuffed with how that started; I can already say that if you are wondering how hard it is, just stop and go for it, the 115pages of tech of the pdf file are there just to frighten you, it is so easy to do that it is almost insulting. The devs of that project did an incredible job at pre-digesting everything for us. 
 

 

[CraigT82]

Nice one, don’t need an autofocuser right now but tempted to give this a go just for the hell of it. Never done anything with arduino.

[FrenchyArnaud]

So my monstrosity is done! Surprisingly, manufacturing the bracket was the most tricky part. I needed quite a few attempts and fidling to achieve the proper belt tension (not too tight, that would block, not too loose, that would slip) 

But! Incredibly it worked perfectly on the very first attempt tonight. I just can't believe it.  The very first run gave me an unbalanced but nice curve,

the second run was as good as I could expect with apparently very, very little backlash.

When I took the 30s test image after the 2nd run, my stars were pin sharp, better than I was ever able to do by eye and much, much faster. 

Pun intended - over the moon. 

 

Edited February 25, 2023 by FrenchyArnaud

[teoria_del_big_bang]

That's a cracking DIY job, as good as anything I have seen 🙂 

Well done 

Steve

[CraigT82]

Nice work! Motorising focusing is the best upgrade you can do to pretty much any scope, once you do it you never look back.  

[FrenchyArnaud]

First try yesterday... And there is no question that ensuring critical focus on every single sub frame makes a massive difference on the final result. I cannot in fact, believe how much of a difference it makes, it's like massively upgrading the optics. This is officially my best galaxy picture so far, and by quite a mile - the Pinwheel M101, 51x 300s + 25D+25F+25DF.

I am overwhelmed by how well this intimidating project went and by how much it actually improved the final result. I can even see 10 or 12 very, very distant galaxies in the background, by my modest standards that is an image that I am really chuffed with and that I never could have done without computer-assisted focusing.  The combination of the permanent pier+EAF is a proper revolution to my imaging process, I have no words to say how pleased I am! 

[Ratlet]

Do you have any pictures of the finished unit?  Are you still using it?  I'm thinking of building one myself...

[FrenchyArnaud]

I am indeed. In fact I have build a 2nd one, with a nema17, for my modify C8N which is currently on the pier. Took me under an hour to do this 2nd one, it is actually real easy. I'll take pic of the 130 AF shortly. 

 

[Ratlet]

Thanks mate.  Would be interested in seeing the control box also, or rather how you've mounted the box that controls the focuser