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OnStep up and running!!!


Egge
 

Hi

finally my STM32 pcb is working and OnStep is up and running. After long waiting, there was also a good night to test with real starry sky - it worked. There are still a few open questions, but at first I want to share my experience and some pictures.

At this stage I also want to thank Howard for OnStep and Khalid for the great support with the STM32 blue pill issu...

my mount: Skywatcher EQ5

STM32 blue pill
Nema17 stepper motors ; they have enough torque
Stepper drivers AA4988 and
DRV8825 worked well, however finally I followed Howards advice and switced to TMC2130 (SPI version) - less noisy and better accuracity

case for pcb was taken from wiki-page; fits very well; side plates were designed on my own...
fixtures for Nema17 (Dec and RA motor) did not fit very well, therefore I decided to design my own for 3D printing - see attached zip-file; I also included the FreeCAD data, in case you want to modify something
GT2: pully 16 and 40; belt 160; on both
axis

as power supply I'm using an old power supply from a laptop (18V; 5A...)

also included in the zip file is a fixture for the controll box to a leg of the mount







Khalid Baheyeldin
 

Good that it all worked in the end ...

Nice conversion too ... it is now in the showcase.


Khalid Baheyeldin
 

The only thing I would improve is the DB9 cables.
Instead of the ones you are using, which require a screw driver, get ones that you can tighten and loosen without a tool.

For example, like this cable.

That way, you don't need a tool in the dark, if you go to a dark site.


Egge
 

On Sat, Oct 17, 2020 at 12:41 AM, Khalid Baheyeldin wrote:
Instead of the ones you are using, which require a screw driver, get ones that you can tighten and loosen without a tool.
yes, fully agree with this... the cables are a temporary solution, since my break-out pcbs for RJ45 did not arrive...


Egge
 

Basic Hand Controller question...

I also have made a basic hand controller... I did not include the resistor network and used in config.h:
#define ST4_INTERFACE                 ON //   
#define ST4_HAND_CONTROL        ON  //

unfortunately the handcontroller does not work...

next step would be introducing the resistor network? will it cause problems if I use it?
I read here that it may cause problems with booting or is this solved?

Unfortunately I have ordered 3.3kOhm (instead of 2.2kOhm)... will it cause problems if the resistance is too high?
in config.h I put:
#define ST4_INTERFACE                 ON_PULLUP
#define ST4_HAND_CONTROL       ON 

thanks in advance...


Egge
 

since I'm not an expert in astronomy, I'm not 100% sure about polar alignment...
first step is a prober aligment of the mount to NCP (using polar scope and an handy app); this works quiete well...

As far as I understood, OnStep also provides a polar alignment - software based?

Do I use the "Align buttons" (green circle) or the "Refine PA" ( yellow circle)?

What are the "Tracking buttons" (blue circles) for?




Unfortunately the described polar align process (wiki / Using Onstep / Alignment / On The Website) is not clear to me. Can someone please describe this more in detail?

thanks
egge


Dave Schwartz
 

The network resistor is required with the Blue Pill. Khalid and I were never able to make it work without one during its development. All of Howard's designs also have one so its not just a good idea, its the law!

A 3.3K part should be OK. It is not as 'strong' as the 2.2K but much better than the internal 'weak' pullup resistors.

I've never heard of any booting problem to do with the pullup resistors on the ST4 signal lines.

The second set of setting you have (with ON_PULLUP) is correct.

On 2020-10-17 5:12 p.m., Egge wrote:
Basic Hand Controller question...

I also have made a basic hand controller... I did not include the resistor network and used in config.h:
#define ST4_INTERFACE                 ON //
#define ST4_HAND_CONTROL        ON  //

unfortunately the handcontroller does not work...

next step would be introducing the resistor network? will it cause problems if I use it?
I read here <https://onstep.groups.io/g/main/topic/27845886?p=,,,100,0,0,0::Created,,st4pullup,100,2,0,27845886,ct=1&ct=1> that it may cause problems with booting or is this solved?

Unfortunately I have ordered 3.3kOhm (instead of 2.2kOhm)... will it cause problems if the resistance is too high?
in config.h I put:
#define ST4_INTERFACE                 ON_PULLUP
#define ST4_HAND_CONTROL       ON

thanks in advance...


andrea tasselli
 

The blue buttons are for the correct tracking rate. For sidereal motion (e.g. stars) use the star one, for the Moon the one with the crescent on and the one with the circle and the dot for solar rate. This because the later two bodies do not move (apparent motion) exactly at the same rate as the stars.

As for the alignment process, you first roughly point the RA axis toward the NCP (North Star) withe the supplied polar finder if you have one, then you got around and point and centre 3 bright stars widely spaced between each other using the process with the 3-star button. Once you have OnStep alignment process done you go to another bright star and centre it. Then press refine PA. and the mount will move to where it would be if the mount was perfectly aligned with the NCP (or SCP). You then use the altitude and azimuth adjustments provided by your mount in order to bring the star back to the centre (of the EP or sensor). Note that you need to be fairly aligned with the celestial pole to be able the keep the said star within the field of view is is a restricted one.

Hope it helps

Andrea


Dave Schwartz
 

Yes, you always have to begin with an alignment at some time. Even if you are forever going to park/unpark a permanently mounted scope, you have to start with an alignment in order to let OnStep build its mount model.

You could use the web interface as you picture below (the green-circled buttons) but you would still have to use some other method to actually do the selection and slewing to the object. The web interface doesn't have an object library so there is no way to tell it you want to go to Vega at such and such RA/DEC coordinates. Probably the better application to use is the Android app. What those green buttons do is tell OnStep you want to begin a 1, 3 or 6-star alignment and after you have set the target and slewed to it, then refined the position using the guide buttons, the Accept button tells OnStep that where it is currently pointing is the coordinated you set as the alignment target. The alignment workflow in the Android app automates the sequence for you - you only have to select the star(s) according to what you prefer/can see, and long-press the align button after centering.

The blue-circled buttons tell OnStep to set the tracking rate as sideral (stars), lunar (moon) or solar (sun).

Refine PA can be used after an alignment to refine your equatorial mount's polar alignment. as in the description, when you GoTo a star near the pole and press Refine PA, OnStep will move the mount to where the star should have been if the mount had been perfectly polar aligned. Then you use the manual altitude and azimuth adjustments to move the star back into the center of the eyepiece and your polar alignment will now be much better.

On 2020-10-17 5:34 p.m., Egge wrote:
since I'm not an expert in astronomy, I'm not 100% sure about polar alignment...
first step is a prober aligment of the mount to NCP (using polar scope and an handy app); this works quiete well...

As far as I understood, OnStep also provides a polar alignment - software based?

Do I use the "Align buttons" (green circle) or the "Refine PA" ( yellow circle)?

What are the "Tracking buttons" (blue circles) for?




Unfortunately the described polar align process (wiki / Using Onstep / Alignment / On The Website) is not clear to me. Can someone please describe this more in detail?

thanks
egge


Egge
 

On Sun, Oct 18, 2020 at 12:07 AM, Dave Schwartz wrote:
A 3.3K part should be OK. It is not as 'strong' as the 2.2K but much better than the internal 'weak' pullup resistors.
Hi Dave,

thanks a lot. I introduced the 3.3K resistor network and the basic hand controller works very well!!! Even with a 2m long cable. No interference with the motors...

Only strange thing what I discovered: during aligning I pressed the North button... telescope moved in one direction. Pressing north button again and telescope moved to other direction - but this was not in home position. Is this normal behaviour?

best regards
egge


Khalid Baheyeldin
 

On Mon, Oct 19, 2020 at 05:10 PM, Egge wrote:
Only strange thing what I discovered: during aligning I pressed the North button... telescope moved in one direction. Pressing north button again and telescope moved to other direction - but this was not in home position. Is this normal behaviour?
Normal.

Read the first question here

https://onstep.groups.io/g/main/wiki/7118


Dave Schwartz
 

AAAARRRGGHHHHH!!!!! First question in the FAQ!!!! https://onstep.groups.io/g/main/wiki/7118

On 2020-10-19 5:10 p.m., Egge wrote:

Only strange thing what I discovered: during aligning I pressed the North button... telescope moved in one direction. Pressing north button again and telescope moved to other direction - but this was not in home position. Is this normal behaviour?


Egge
 

Thanks Andrea and Dave

for the hints with alignment procedure... luckily today there were a few visibel stars, so I could start with the aligment procedure...

Since I have an iPhone, I can not use Android apps... On iPhone there is an app called "gotomode" and it seems to be compatible with Onstep. I tried it and it seemed to work, however I prefer working with laptop and Stellarium.

Things what I did for alignment (just to repeate in my words):
1. I did a rough polar alignment on the mount with polar scope; moved telescope to NCP (counterweights facing straight down)
2. started OnStep (web-interface); time and location settings; started tracking
3. started Stellarium and connected it to OnStep (via Ascom driver - also time and location settings)
4. pressed in OnStep (web-interface) the button 3-star alignment
5. selected in Stellarium a bright star and made a GoTo; fine-tuned with basic hand controller; after that there was a missalignment of selected star and actual telescope position in Stellarium
6. pressed "accept" in OnStep webinterface - after this the selected star and telescope pointer were aligned again
7. repeated step 5 and 6 two more times with two different stars at different sections on sky
8. select a star in Stellarium close to NCP and  do a GoTo; press "refine PA"; telescope moves; use PA-alignment of mount to bring star back in center

I assume for this, the highest magnification ocular should be used?

Some questions came up:
- step 4 is only done once?
- is there any indication, if the alignemtn is accepted by OnStep or when it is finished? e.g. beep?
- is there any indication about amount of stars aligned? if you do a 1-star alignment, then it is easy. However if you do a 6-star alignement and you get confused with counting???

The issues I had during this alignement procedure:
- 2 or 3 times I had the impression, that OnStep did not accept the alignment
- two times there was only a 1-star possible (see sreenshot below); this disapeared after powering off and on again...
- I never got it 100% exact - I will follow up later on "backlash", maybe this is my issue
- in a few cases, moving towards "north" with basic hand controller and/or OnStep webinterface, the telescope moved in one direction and when pressing same button again, telescope moved in other direction



When going back home (home position) after an alignment, the counterweight was not exactly facing down any more - could this be a hint, that my time or location setting is not correct?



Egge
 

On Mon, Oct 19, 2020 at 11:22 PM, Khalid Baheyeldin wrote:
Normal.

Read the first question here

https://onstep.groups.io/g/main/wiki/7118
Thanks Khalid,

yes I had exactly this before, when I was close to NCP... I also read the FAQ and understood the reason. But today it happend when I was not even close to NCP or in home position... Therefore I was asking... I'm sorry for this... So in this case the explantion is probably that the RA axis was on the same position as for NCP??? sorry, I'm missing the correct astronomical terms.


Khalid Baheyeldin
 

The procedure you followed is accurate.
If you plan to autoguide, the RefinePA step may not be necessary. Otherwise, it helps with accurate polar alignment.

Instead of clicking Accept, you can also do a 'Sync' from somewhere else (Gotomote Stellarium or ASCOM).
That way, you only start the align from the web interface, then continue from whatever other application you feel best.
When you are done, the web interface Status page will show the Alt and Az offsets.

And you can also do the alignment using plate solving, if you have software that has this feature.
For example, I use KStars, and there is a feature where you slew to an object, then plate solve and sync on the solution coordinates.
I do this from the laptop on 3 stars and I am done.
If you don't use plate solving, then ignore this part.

For the counter weight offset, it looks to me like one third of one quarter of a circle. So it is 15 degrees. If it is so, then it looks like the UTC offset is not correct (summer time vs. winter time).


Egge
 

On Tue, Oct 20, 2020 at 12:04 AM, Khalid Baheyeldin wrote:
For the counter weight offset, it looks to me like one third of one quarter of a circle. So it is 15 degrees. If it is so, then it looks like the UTC offset is not correct (summer time vs. winter time).
Thank you Khalid,

I checked and indeed I had the winter-time... unfortunately today it's very cloudy, so I can not check it with real stars...
do I change it on the OnStep website or better on the Ascom driver?

plate solving is not (yet) planned... I want to start with the basics...


Khalid Baheyeldin
 

On Tue, Oct 20, 2020 at 04:24 PM, Egge wrote:
I checked and indeed I had the winter-time... unfortunately today it's very cloudy, so I can not check it with real stars...
do I change it on the OnStep website or better on the Ascom driver?
I think ASCOM will send it to OnStep, so try it there.
You can verify that it did by checking the web interface for OnStep or the Android app (under Observing Locations).