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My new setup, SV80 Access

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#1 Kevin Ross

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Posted 11 July 2019 - 08:15 PM

So I've been having fun with the new setup, a Stellarvue SV80 Access ED Apo, with .8x FF/FR. Sitting atop an Atlas mount with Rowan belt mod.

 

I tried to do a good job with cable management. Got most of the cables tucked away. Using a cheap Power Pole distribution block to power everything.

 

20190711_202912-sm.jpg

 

My Raspberry Pi runs everything. It even has a stepper motor controller, for controlling autofocus. That's what the DB9 connector is for on the Pi.

 

The guidescope uses clamps to attach to the main OTA's dovetail. The reason for the clamps, and not just screwing the rings directly to the dovetail, is because I want to easily move the guidescope to my other OTA, the Orion 8" f/3.9 astrograph.

 

20190711_203046-sm.jpg

 


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#2 Kevin Ross

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Posted 11 July 2019 - 08:17 PM

And the imaging choo-choo. An ASI1600MM Pro with ZWO EFW, and Stellarvue .8x FF/FR. The FF/FR is held in place in a 2" eyepiece holder. I actually get less tilt using that than the rotator they sell, which allows you to screw the FF/FR into the focuser. Grrr. Oh well. This setup works well enough.

 

20190711_203031-sm.jpg


I access the Raspberry Pi via WiFi. Those of you that are Pi-savvy may be wondering why the USB WiFi adapter when the Pi has built-in WiFi? Two reasons, actually. Reason one, the built-in has a terrible antenna, and therefor terrible range. Reason two, now that I have two WiFi adapters, I set it up so the built-in is a hotspot, and the second connects to my home WiFi. So when I'm at home, it automatically connects to my home WiFi, and I can access it from my computers indoors no problem. But if the home WiFi is nowhere to be found, then the built-in hotspot lets me connect my laptop to it via WiFi quite easily. The limited range of the internal WiFi is fine when using it as a hotspot, since in that case I'll be very close to the scope anyway.

 

I have only a single cable hanging off the scope, a power cable (can't avoid that). When at home, I just plug it into the AC adapter you see. If I were to take this on the road, I could plug it into a battery.

 

20190711_203105-sm.jpg

 

My next project is adding autofocus. I have the stepper motor, the Pi has the stepper controller. I have a 3D printer for the bracket to hold the stepper onto the focuser. I'll post some pictures when I get that done.

 


Edited by Kevin Ross, 11 July 2019 - 08:19 PM.

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#3 44maurer

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Posted 11 July 2019 - 08:22 PM

waytogo.gif waytogo.gif waytogo.gif


Edited by 44maurer, 11 July 2019 - 08:22 PM.


#4 Kevin Ross

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Posted 11 July 2019 - 08:29 PM

BTW, that guidescope used to be black! I guess that's what leaving it out in the sun does to it.



#5 Eric Horton

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Posted 11 July 2019 - 08:32 PM

Very nice.  curious about the software you are using on the Pi?  I have one with Astroberry on it but has not been the most stable and definitely not enough horsepower.  I tend to stay with my laptop.

 

Thanks



#6 Kevin Ross

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Posted 11 July 2019 - 08:38 PM

I use KStars/Ekos/INDI. The Pi is very limited in RAM, which makes running KStars difficult. I run KStars on my laptop, and it communicates with INDI and the hardware over WiFi. I'm getting a new Pi with 4 GB RAM, which will make running KStars on the Pi a piece of cake.



#7 TelescopeGreg

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Posted 11 July 2019 - 08:53 PM

Very nice, especially the clever use of the Pi.  I tried Kstars / Ekos, and decided it was just too much for the Pi 3B platform, and I prefer to not require a laptop.  Instead I run CCDciel, ASTAP, and PHD2 on the Pi. I either use the laptop or my cell phone for getting things going, then turn them off.  I might revisit this in light of the Pi 4...

 

What stepper controller hat are you using, and what drives it?



#8 Kevin Ross

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Posted 11 July 2019 - 08:58 PM

I use this stepper controller: https://www.adafruit.com/product/2348

 

You can see a red/black wire hanging out of the Pi. That's for 12V in, from the Power Pole distribution block, to power the stepper.

 

There's an INDI driver for it made by the same guy that made Astroberry.



#9 Eric Horton

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Posted 11 July 2019 - 09:09 PM

Awesome  Thanks!!



#10 Kevin Ross

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Posted 13 July 2019 - 10:38 PM

Okay, I got a DIY autofocus solution working!

 

I modeled up some parts iteratively. First I modeled the part that interfaces to the stepper motor, and made sure it fits. Then I modeled the part that attaches to the telescope, make sure it fits. Then I made a prototype of all of it together.

 

This photo shows the various stages of my prototyping. The final bracket is just one piece, not an assembly. All the small pieces you see are just me modeling up little pieces and seeing how they fit.

 

20190713_232105.jpg

 

I felt the bracket was a little too thin, and flexed too easily. So the final bracket, seen below, is much beefier.

 

20190713_215303.jpg

 

And here it is with the stepper motor attached. The DB9 connector I wired up the same as my Moonlite focuser, so I can use the same controller for both focusers. The controller I'm using is a stepper motor HAT for the Raspberry Pi. Since I'm already using a Pi for my scope-side computer, it only cost an extra ~$30 for a focus controller! smile.gif

 

20190713_221041.jpg



#11 Kevin Ross

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Posted 13 July 2019 - 10:42 PM

Since it's currently night, and my telescope is currently busy imaging, I didn't take a photo of the focuser mounted on the scope. I will do that tomorrow.

 

But in the meantime, here's the result of an autofocus run.

 

(Click the image if you want to be able to read the text)

 

autofocus-ekos.png

 

So the final bill of materials:

 

$19 Stepper motor

$6 Shaft coupler

$9 DB9 connector

 

Plus the things I already had:

$23 Stepper motor HAT

$30 Raspberry Pi

 

So if you have a 3D printer, and don't mind some DIY, this is a very inexpensive way to add autofocus to an existing focuser.

 

I'll add a photo tomorrow of the setup on the scope.


Edited by Kevin Ross, 13 July 2019 - 11:07 PM.


#12 Kevin Ross

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Posted 14 July 2019 - 01:46 PM

As promised, here's a photo of the motor attached to the focuser. I only removed the fine-focus knob and attached the stepper to that. I've seen some solutions that attach to the course-focus knob. Of course those solutions use a geared-down stepper motor.

 

I think I need to flip the motor around, so the wires are to the back.

 

20190714_143158.jpg

 

And here's the other side, plugged into the Pi

 

20190714_143222.jpg

 

Thanks for looking!

 


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#13 Tom K

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Posted 13 August 2019 - 07:56 AM

Kevin - I have an SV102 Access on the way and have been looking for a way to mount a stepper to my new scope.   I already use the PnP Focus Arduino system successfully on some Moonlite focusers on my other OTAs but Moonlite provides a bracket and mounting holes on their mounts.  I have a couple of questions about yours.

 

- Have you had any issues being connected to the 10:1 knob?  I have read elsewhere that this is not the recommended practice but could never figure out exactly why that would be.

 

-  Do you have the STL file available on thingverse or similar website for use by others?   I would certainly be interested in checking that out.

 

Thanks

 

Tom



#14 Kevin Ross

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Posted 13 August 2019 - 10:28 AM

I think the reason (not sure, just guessing) for not using the 10:1 knob is it might introduce more backlash, or possibly slip if it isn't connected by gears, but rather friction. But I haven't seen any such issues with my setup. Of course your mileage may vary.

 

I'd be happy to send you the Fusion 360 file, or an STL file if you prefer. Send me a PM with your email address.

 

If you do 3D print a bracket, make sure you don't use PLA! Use PETG or ABS. PLA will get soft in the sun, especially if you use black filament. Maybe white PLA would do better, since it doesn't absorb as much heat in the sun as black would. I did my prototyping with PLA, but the final bracket is PETG.



#15 Tom K

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Posted 13 August 2019 - 02:41 PM

PM sent!   My telescope is virtually never in the sun as I have it in a tilt off enclosure that does not get opened until after the sun sets.   I will see about different filaments though, but I have to have a buddy print it for me, so I am not sure how much say I am going to have in the filament.

 

Thanks!



#16 Kevin Ross

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Posted 14 August 2019 - 12:53 AM

If you keep it out of direct sunlight, PLA should be okay, but don't hold me to it! :)


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