TOTAL noob trying onstep #EQ3 (Exos-Nano) #EQ3


Juan Sebastian
 

Hi guys,

Im a total noob here, this is going to be my first time building something complex (and soldering it), so i wonder if someone can carry me trougth this journey to build my first go-to system, let me give you more info:

1) Im from Bogota, Colombia, everything regarding astronomy is expensive here, but so far i manage to do some planetary astrophotograpy, now that i want to do deepsky, i need a tracking system (with an autoguiding camera) so i bougth a 50mm guidescope (https://a.aliexpress.com/_mNJ48xD) + sv305pro guiding camera (https://a.aliexpress.com/_mPx8535)

2) My current rig is a sv503 80ED f7 around 4kg + EXOS-NANO (EQ3) mount (https://explorescientificusa.com/products/exos-nano-mount-fl-exosnanot1-00?_pos=1&_sid=b3c0b87fb&_ss=r)

3) Please check this list and tell me if im missing something that i need, or if i should buy something better:

STM32 - $25.00 Everything to build the BluePill, except the BluePill. (https://www.stmbluepillkits.com/p/kits.html)
 
Thank you for your help!


Khalid Baheyeldin
 

On Wed, Feb 17, 2021 at 02:36 PM, <jbastian.casas@...> wrote:
- x2 NEMA 17 42BYGHM809, 400 steps, 0.9°, 3v, 1.7A, 4.2 kg/cm
Since your mount is on the small side, you should get the 0.9A 400 step motor,
which will use less current, dissipate less heat, and compatible with recommended
drivers (as below).

- x2 DRV8825 drivers
Don't use these. There are better options.
If you get the 0.9A motors, you can use the LV8729 drivers instead.

- Arduino UNO R3
That one is useless for OnStep. Don't buy it.

or STM32F103 STM32F103C8T6 C BluePill
You need to make sure it is the 128K Blue Pill, otherwise it will not work. 
There is also the F303CC (RobotDyn), which may be hard to get, but it has double the flash
memory, so it is future proof, and also is much faster than the Blue Pill.


Juan Sebastian
 

Ok i found the LV8729 drivers in the country (https://www.mactronica.com.co/driver-lv8729-controlador-motor-paso-a-paso)

And i think this is the bluepill 128k also here in Colombia (https://articulo.mercadolibre.com.co/MCO-569052368-modulo-de-placa-de-desarrollo-stm32-stm32f103c8t6-arm-_JM)

So with that, and this i have everything needed to build it?

STM32 - $25.00 Everything to build the BluePill, except the BluePill. (https://www.stmbluepillkits.com/p/kits.html)


Khalid Baheyeldin
 

For the Blue Pill module, I hope it is really 128K. Often sellers do not know what they are selling, since they are advertised as 64K, and having more flash memory was a free bonus.

You still have the 1.7A motor, and the LV8729 cannot drive it at full current.
You are better off with this 0.9A motor which the LV8729 can drive at any current.
Check if you can find it locally.


Drew 🔭📷🚴‍♂️
 

On Wed, Feb 17, 2021 at 04:26 PM, Khalid Baheyeldin wrote:
You still have the 1.7A motor, and the LV8729 cannot drive it at full current.
I would not worry about that. The main reason to not use the motor is mechanical (the longer length). there is little or no penalty running under its rated current. After all, it is what we almost always suggest. I now buy the 1.7A motors with a eye toward the possibly of needing them for future projects.

I think it is more important to get 400 step/rev motors.


Juan Sebastian
 

Hi Drew & Khalid!!

1) I found here in the country the 128k bluepill (with proof) - Item Bought  - OK

2) I got the drivers x2 LV8729 form the same seller - Bought - OK

3) Here are the motors x2 17HM15-0904S -free shipping to Colombia- (https://www.amazon.com/gp/product/B00W98OYE4/ref=ox_sc_act_title_1?smid=AWQBCGWISS7BL&psc=1) - Waiting your confirmation to buy them (im going to stick with these since they are cheaper)

4) STM32 - $25.00 Everything to build the BluePill, except the BluePill. (https://www.stmbluepillkits.com/p/kits.htmlWaiting your confirmation to buy it

What im missing? just wires? and a lot of building time?


Drew 🔭📷🚴‍♂️
 
Edited

This is the one I suggest, just a few bucks more: https://www.amazon.com/STEPPERONLINE-Bipolar-Stepper-0-9deg-62-3oz/dp/B00PNEQMLY?ref_=ast_sto_dp Again, you will need to check if you have the room for it. It is more powerful than needed for your mount, the one you show will work fine also.

You are  missing all the details items. Timing belts, pulleys, connectors, STM32 case. Do you have a 3D printer? You will need to build motor brackets for you mount.

Take a look in the Wiki. I believe yours is in the Skywatcher EQ3-2, Celestron CG4 section of the "Built with OnStep" section.


Juan Sebastian
 

Hi Drew!

 

Yeah i waas reading about timing belts, pulleys reduction and other stuff from someone who tried onstep on the same mount (https://onstep.groups.io/g/main/topic/help_needed_choosing_gearing/31482533?p=Created,,,20,1,0,0::,,,0,0,0,31482533&jump=1)

:( sadly i do not have a 3d printer (but it seems like doing some cardboard stuff could work)

About the brackets, seems like these will work :
- x2 NEMA 17 bracket (https://www.bigtronica.com/centro/motores/paso-a-paso/565-base-motor-paso-a-paso-nema-17-5053212005658.html)

 

BTW Drew i will start doing some AP but with pure visualy proposes (take single long exposures to be able to "see" things that otherwise are not possible), but short-medium term i wish to star doing some stacking and post-procesing (to do autoguide it seems that im going to need extra stuff to upgrade this onstep rigth?)

 


Juan Sebastian
 

Hi Khalid,

1) I already filled and sent the order form for a STM32 kit
2) I got the 128k bluepill (proof attached)
2) My RA primary worm screw transver ratio is 138:1 and my DEC primary worm screw transver ratio is 88:1 with that in mind an looking for a 3:1 ratio im going to get 14720 in RA, and 9386 in DEC (is that ok for some not-award winning AP?)
For that i need to buy:


Khalid Baheyeldin
 

On Fri, Feb 19, 2021 at 02:57 PM, <jbastian.casas@...> wrote:
My RA primary worm screw transver ratio is 138:1 and my DEC primary worm screw transver ratio is 88:1 with that in mind an looking for a 3:1 ratio im going to get 14720 in RA, and 9386 in DEC (is that ok for some not-award winning AP?)
With a short focal length optical tube, maybe the DEC being less than 12,800 will not be an issue.
You can also increase the microsteps for the DEC, more than the RA, and see if that works.
You have to try all that and see ...


Juan Sebastian
 

Thanks Again Kalid, ill check the microsteps or change the ratio and pulleys to make it go over 12.800 in RA and DEC, maybe i will use 48T to 12T, that gives me 12515 on DEC, and 48T/16T for RA to get 14720

I saw your FYSETC S6 video, that feels easier than the bluepill, im going to try that first *no soldering!!!


Khalid Baheyeldin
 

On Fri, Feb 19, 2021 at 09:11 PM, <jbastian.casas@...> wrote:
Thanks Again Kalid, ill check the microsteps or change the ratio and pulleys to make it go over 12.800 in RA and DEC, maybe i will use 48T to 12T, that gives me 12515 on DEC, and 48T/16T for RA to get 14720
If you already have pulleys, then use what you have, test it first, then see how it performs.
Based on that you can evaluate whether you need different pulleys or not.
Also, the larger the pulley, the more likely it will hit something in the mount in certain position.
So make sure you have room for whatever size pulley you use.

I saw your FYSETC S6 video, that feels easier than the bluepill, im going to try that first *no soldering!!!
I will contact you separately on that.