Something a little different


njgood51
 

I thought you might like to see my Onstep controled home built friction driven fork mount. Onstp version 4.2 with the new ascom driver. STM32 bluepill board with DLV8729 drivers on both axis and DRV8825 for the cheap generic DC focuser. The steppers are are Nema 17 with 200 steps. RA final reduction 2630.055:1 at 16 steps giving 23378.266 steps per degree. Dec has a 12:1 worm-wheel to a17.9:1 friction drive 32 steps giving 22912 steps per degree. The scope  is a rare Cape Newise 200mm F6. Its only 62mm long. I dont have anywhere to set up at home so i travel to my sites and the mount needed to trasport easily. Everything is powed by a 12v to 240v inverter connected to a 12v 110AH leisure battery. This powers the 19v psu for onstep and tops up the laptop battery. Also 12v for the demistors and 8.4v for the cannon 500d camera. An observing session starts with assembling the scope , connect the cables and start laptop. Polar alignh with Sharpcap, Switch on onstep connect to laptop with WI-FI, manualy swing the scope to somwhere overhead, start tracking focus take a shot do a blind solve in APT, sync, then in APT do a GoTo++ to my target, start PHD2 then use APT for my imageing session. Its taken quiet sometime to get to this stage after going down some blind allys. Onstep transformed the scope. I would like to take this oppertunity to thank Howard, Kahlid, Dave for the kits and all the others who have taken the time and trouble to contribute to onstep without whoms help this project of mine would not be where it is today.


Mike Ahner
 

Very nice!! And very interesting, impressive design!

What material are you using for the friction drive parts? I see wood for the large wheel. How well does it work while slewing? What slew speeds can you get? The spreadsheet shows 1 deg/sec.

Thanks for the pictures!
-Mike


tnut55
 

I like it!  I always enjoy looking ay pure DIY scopes.


On Fri, Nov 27, 2020 at 10:19 AM, Mike Ahner
<mahner@...> wrote:
Very nice!! And very interesting, impressive design!

What material are you using for the friction drive parts? I see wood for the large wheel. How well does it work while slewing? What slew speeds can you get? The spreadsheet shows 1 deg/sec.

Thanks for the pictures!
-Mike


Khalid Baheyeldin
 

Thanks for sharing this. Very unique!
It is now in the showcase page.

On Fri, Nov 27, 2020 at 08:36 AM, njgood51 wrote:
Everything is powed by a 12v to 240v inverter connected to a 12v 110AH leisure battery. This powers the 19v psu for onstep and tops up the laptop battery. Also 12v for the demistors and 8.4v for the cannon 500d camera.
I got this part: 12V 110AH battery -> inverter -> 240V
Then what?
How is OnStep powered from 240V?
By demistor, you mean dew heaters?

An observing session starts with ... manualy swing the scope to somwhere overhead, start tracking focus take a shot do a blind solve in APT, sync, then in APT do a GoTo++ to my target.
By "manually swing the scope", you mean guiding from the Android app or an SHC?
Or you mean releasing the clutch, and moving the tube by hand to point near the zenith?

I am assuming the former, since without encoders, OnStep will have no way of tracking where you are.

I use a similar procedure, and OnStep 4.x now has a nice feature: if you entered the date and time (or it is read from the RTC or GPS), then you can slew right away, without needing to start an align. I point to a star, but the difference is that I have to use Spiral Search to find it, so I can focus using a Bahtinov mask.
After that I do a plate solve and Sync, and then also center using plate solving.


njgood51
 

Thank you mike
The RA disk is a dence hard 20mm thick plywood used for flooring in trucks. The gearbox i turned out of 145mm dia by 24 thick alloy disks. The first drive shaft is a 12mm stainless shaft. It works very well. I can slew from horizon to horizon and the object will be in field of view of the camera. I can slew at higher speeds but the stepper rpm gets eccesive (800+ rpm at 2). I dont realy need to slew at high speeds as i only image 2-3 objects a night and if it takes a minet or so longer i'm ok with that. What i would like to do is replace the wood disk with a water cut 20mm thick alloy disk but the buget wont go to that at the moment.
Nick








---- On Fri, 27 Nov 2020 16:19:23 +0000 Mike Ahner <mahner@...> wrote ----

Very nice!! And very interesting, impressive design!

What material are you using for the friction drive parts? I see wood for the large wheel. How well does it work while slewing? What slew speeds can you get? The spreadsheet shows 1 deg/sec.

Thanks for the pictures!
-Mike






njgood51
 

Hi kalid
Didnt exsplain well enough. The inverter takes 12volts changes it to 240 50hz houshold supply. Then i can plug into it any thing runs on mains power , in my case the laptop battery charger and a 19v wall mart to power Onstep. Yes brain freeze i mean dew heaters. I can point the scope to any point in the sky manualy by releasing the drives (clutches). I dont point it at any thing in particular then start the tracking do a plate solve in APT and the telescope then knows where its pointed. I can then do a slew to any object usualy a star so i can focus  APT has a good focus aid or i will liveview and magnify the star and focus on that. I dont do any star alighn or spiral search. If i do the slew to the object with GoTO++ in APT , in two or three moves it will be dead center.



---- On Fri, 27 Nov 2020 16:40:48 +0000 Khalid Baheyeldin <kbahey@...> wrote ----

Thanks for sharing this. Very unique!any thing
It is now in the showcase page.

On Fri, Nov 27, 2020 at 08:36 AM, njgood51 wrote:

Everything is powed by a 12v to 240v inverter connected to a 12v 110AH leisure battery. This powers the 19v psu for onstep and tops up the laptop battery. Also 12v for the demistors and 8.4v for the cannon 500d camera.
I got this part: 12V 110AH battery -> inverter -> 240V
Then what?
How is OnStep powered from 240V?
By demistor, you mean dew heaters?


An observing session starts with ... manualy swing the scope to somwhere overhead, start tracking focus take a shot do a blind solve in APT, sync, then in APT do a GoTo++ to my target.
By "manually swing the scope", you mean guiding from the Android app or an SHC?
Or you mean releasing the clutch, and moving the tube by hand to point near the zenith?

I am assuming the former, since without encoders, OnStep will have no way of tracking where you are.

I use a similar procedure, and OnStep 4.x now has a nice feature: if you entered the date and time (or it is read from the RTC or GPS), then you can slew right away, without needing to start an align. I point to a star, but the difference is that I have to use Spiral Search to find it, so I can focus using a Bahtinov mask.
After that I do a plate solve and Sync, and then also center using plate solving.






njgood51
 

Thanks Mike
I have always enjoyed making my own scopes trying different ideas. But its Onstep that has taken this to new level. Building somthing then have Onstep control it is for a me revalation.
Nick



---- On Fri, 27 Nov 2020 16:22:55 +0000 tnut55 via groups.io <tnut55@...> wrote ----

I like it!  I always enjoy looking ay pure DIY scopes.



On Fri, Nov 27, 2020 at 10:19 AM, Mike Ahner
<mahner@...> wrote:
Very nice!! And very interesting, impressive design!

What material are you using for the friction drive parts? I see wood for the large wheel. How well does it work while slewing? What slew speeds can you get? The spreadsheet shows 1 deg/sec.

Thanks for the pictures!
-Mike






Sylvain Mennessier
 

ohhh it's beautiful, great work !!!


tomofreno2000
 

Nice nj!


tomofreno2000
 

How do you apply force between DEC disk and drive wheel to get sufficient friction?


njgood51
 

Hi Tomofreno,
Its very basic. The DEC drive unit pivots on a bolt through the drive unit backplate. Under the drive unit base is a fixed plate that has a 6mm bolt tapped through  it that can be screwed out to push the unit and drive shaft against the DEC wheel. When i have enough pressure another bolt in a curved slot through the backplate can be tightened along with the pivot bolt to lock it all in place.
Nick



---- On Sat, 28 Nov 2020 15:37:00 +0000 tomofreno2000 via groups.io <tomofreno2000@...> wrote ----

How do you apply force between DEC disk and drive wheel to get sufficient friction?






George Cushing
 

Pure genius. Even a cup holder in the RA drive disk!

Virus-free. www.avg.com


Jay Murphy
 

Solid work. Nicely done.