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Sending instruction to my dual motors, without GOTO?

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#1 Yourjones

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Posted 14 June 2021 - 10:00 AM

Hi folks

 

I have dual motors on an EQ3 mount. It can only be guided by PHD2 via “on camera” using an ST4 cable connecting the guide camera with the small hand controller. My imaging camera is a Nikon DSLR; guide scope is a ZWO ASI224MC.

 

Because this is not a GoTo system, when I am lost in the star field, I have to resort to plate solving using PlateSovle2.28. I then get the coordinates of the center of the image I feed to PS2.28. Those coordinates are pretty helpful, as I’ll then know in which RA/DEC I need to turn my scope. However, I can only manually do the adjustment and rely on “feeling”. When I “feel” I’m almost there, I’ll take another picture and feed it to PS2.28, and the whole cycles runs again.

 

With my setup, is there a way I can instruct my motors to move by a given amount, say how many arcmins in DEC and how many seconds in RA? I don’t remember PHD2 can do this, but it does know how much it wants my motors to go, well… of course, for the purpose of guiding.

 

Thanks a lot!

 

Lu



#2 astrokeith

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Posted 14 June 2021 - 10:39 AM

Hi folks

 

I have dual motors on an EQ3 mount. It can only be guided by PHD2 via “on camera” using an ST4 cable connecting the guide camera with the small hand controller. My imaging camera is a Nikon DSLR; guide scope is a ZWO ASI224MC.

 

Because this is not a GoTo system, when I am lost in the star field, I have to resort to plate solving using PlateSovle2.28. I then get the coordinates of the center of the image I feed to PS2.28. Those coordinates are pretty helpful, as I’ll then know in which RA/DEC I need to turn my scope. However, I can only manually do the adjustment and rely on “feeling”. When I “feel” I’m almost there, I’ll take another picture and feed it to PS2.28, and the whole cycles runs again.

 

With my setup, is there a way I can instruct my motors to move by a given amount, say how many arcmins in DEC and how many seconds in RA? I don’t remember PHD2 can do this, but it does know how much it wants my motors to go, well… of course, for the purpose of guiding.

 

Thanks a lot!

 

Lu

What are you running the plate solve & PHD2 on?



#3 Yourjones

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Posted 14 June 2021 - 08:23 PM

What are you running the plate solve & PHD2 on?

Hi Keith

 

Thanks for asking. I run both mentioned programs and the BackyardNikon on a Win10 laptop with pretty out-of-date hardware. Nonetheless, they run quite smoothly at the same time.

 

The Laptop is connected via USB3 with my guide camera, which in turn is linked with the small no-brand hand controller using ST4, which in turn drives the two motors. My main imaging camera - the DSLR is connected via USB to another slot on my laptop, so I can operate on it using BackyardNikon.

 

I'm wondering if I can fool PHD2 that the target star is at a position, so it can send electric pulses to the guide camera to the no-brand hand controller to the motors, I can sort of semi-goto? Sorry if that doesn't make sense at all. Or is there another approach?

 

Lu



#4 hcf

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Posted 14 June 2021 - 08:50 PM

Theoretically you could write a program which does GoTo using the ST4 on your laptop.

The biggest problem, even if you could do this, is that the ST4 commands work around the tracking speed (15"/s). This is very slow for GoTos.

 

An alternative approach is to build your own controller with newer motors. It is not very expensive, but needs some working knowledge of electronics and computers.

Take a look at ONSTEP

https://onstep.group.../main/wiki/4414

 

I have done the iterative platesolve/manual movement by hand, and it gets easier if you use the RA/Dec setting circles to measure approximately the amount you need to move.

 

In the end I built a platesolving GoTo which automates the same concept.

https://www.cloudyni...-project-ps-g2/


Edited by hcf, 14 June 2021 - 08:56 PM.

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#5 Yourjones

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Posted 14 June 2021 - 10:26 PM

Theoretically you could write a program which does GoTo using the ST4 on your laptop.

The biggest problem, even if you could do this, is that the ST4 commands work around the tracking speed (15"/s). This is very slow for GoTos.

 

An alternative approach is to build your own controller with newer motors. It is not very expensive, but needs some working knowledge of electronics and computers.

Take a look at ONSTEP

https://onstep.group.../main/wiki/4414

 

I have done the iterative platesolve/manual movement by hand, and it gets easier if you use the RA/Dec setting circles to measure approximately the amount you need to move.

 

In the end I built a platesolving GoTo which automates the same concept.

https://www.cloudyni...-project-ps-g2/

Thanks for sharing. I admire these DIY GOTO efforts and believe the outcome is exactly what lots of amateur astronomers expect. Although it's far beyond my reach in knowledge, I have saved the pages for further digestion. Thank you so much!

 

Given my limited knowledge and gears, I am thinking it more practical to accept the advice of using the setting circles in combination with plate solving. I probably won't need too many iterations until I somehow locate the target in the view.

 

I'm using my rudimentary thinking to try to devise a makeshift technique. Is this going to work out?

 

1. Orient my imaging camera in line with the scope, so any stars' horizontal motion is along DEC, and vertical is RA.

2. Place a bright star, say Vega on the top/bottom edge of the FOV so I can see it in live view.

3. Press RA+ or RA- on the small hand controller the moment I begin timing.

4. Average the time it takes for the star to travel from one edge of the field to the other, and divide it by the height of my FOV to get the "seconds per arcmin" or even finer units.

5. Do the same on DEC direction, taking backlash into consideration.

 

So I can coarsely math the time I need to press on the RA and DEC button if I want to move my scope to the desired target. This sounds like using abacus and typewriter in the information world, but I'll give it a try as I think it's going to get me somewhere near my target. 

 

Lu


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#6 hcf

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Posted 14 June 2021 - 10:52 PM

Yes, estimating the speed will be helpful too.

If your motors have clutches, ie they can be disengaged from the worm shafts easily, you could try the slow motion knobs too. It is easier to estimate how much to turn the knobs for a particular degree.

 

The manual method is not too bad for AP, because you spend a lot more time photographing than you spend framing the target.


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#7 astrokeith

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Posted 15 June 2021 - 06:37 AM

Thanks for sharing. I admire these DIY GOTO efforts and believe the outcome is exactly what lots of amateur astronomers expect. Although it's far beyond my reach in knowledge, I have saved the pages for further digestion. Thank you so much!

 

Given my limited knowledge and gears, I am thinking it more practical to accept the advice of using the setting circles in combination with plate solving. I probably won't need too many iterations until I somehow locate the target in the view.

 

I'm using my rudimentary thinking to try to devise a makeshift technique. Is this going to work out?

 

1. Orient my imaging camera in line with the scope, so any stars' horizontal motion is along DEC, and vertical is RA.

2. Place a bright star, say Vega on the top/bottom edge of the FOV so I can see it in live view.

3. Press RA+ or RA- on the small hand controller the moment I begin timing.

4. Average the time it takes for the star to travel from one edge of the field to the other, and divide it by the height of my FOV to get the "seconds per arcmin" or even finer units.

5. Do the same on DEC direction, taking backlash into consideration.

 

So I can coarsely math the time I need to press on the RA and DEC button if I want to move my scope to the desired target. This sounds like using abacus and typewriter in the information world, but I'll give it a try as I think it's going to get me somewhere near my target. 

 

Lu

Does your 'no brand' have a speed selector. usually there is x0.5, x2 and x8 or x16. If so it opens up some options.


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#8 Yourjones

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Posted 16 June 2021 - 09:01 AM

Does your 'no brand' have a speed selector. usually there is x0.5, x2 and x8 or x16. If so it opens up some options.

Hi Keith

 

Believe or not, my no-brand has a selection of x1, x10, x100 and x800. I only use the x10 speed. When I do need to move far, I unfasten the clutches of the mount and manually turn the mount-head.

 

Are there some options that I, a technical illiterate, can take advantage of?

 

Lu



#9 astrokeith

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Posted 16 June 2021 - 09:34 AM

Hi Lu,

 

Given your self confessed technical illiteracy, the options have just got much less!

 

Your previous post about coarsely math the time needed to press a button, is the most basic. But helped by having a range of speeds.

 

You could use a spreadsheet (are you Windows or Mac?). Input target position, input solved solution, and get it to calculate accurately the button press time (and which button!) for each speed you have. You could then choose which speed to use to give you the best chance of getting close to the required button time. ie not too fast a speed. You are bound to need another iteration, at a slower speed.

 

I cant think of anything else that you might be comfortable tackling?

 

Find a friend who can rewire your handbox and write some code? smile.gif


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#10 bips3453

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Posted 16 June 2021 - 10:19 AM

Or you can upgrade to a GoTo controller.


Edited by bips3453, 16 June 2021 - 10:19 AM.

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#11 Yourjones

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Posted 16 June 2021 - 07:27 PM

Hi Lu,

 

Given your self confessed technical illiteracy, the options have just got much less!

 

Your previous post about coarsely math the time needed to press a button, is the most basic. But helped by having a range of speeds.

 

You could use a spreadsheet (are you Windows or Mac?). Input target position, input solved solution, and get it to calculate accurately the button press time (and which button!) for each speed you have. You could then choose which speed to use to give you the best chance of getting close to the required button time. ie not too fast a speed. You are bound to need another iteration, at a slower speed.

 

I cant think of anything else that you might be comfortable tackling?

 

Find a friend who can rewire your handbox and write some code? smile.gif

Hi Keith

 

That does open up my mind! I have MS Excel on my Win10 laptop. The formulae are what I do know a bit of, and I believe I can write a few equations in the cells of the spreadsheet, so that a timed button-pressing can be given when I input the target coordinates and those of the plate-solving result.

 

I know how to use the setting circles, so I won't be too far from my target after manually move the mount head. I'll still use the x10 speed to slowly slew to my target with the help of the the formulae in Excel.

 

I'll give it a try. Thank you so much!

 

Lu


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#12 astrokeith

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Posted 17 June 2021 - 02:16 AM

Hi Keith

 

That does open up my mind! I have MS Excel on my Win10 laptop. The formulae are what I do know a bit of, and I believe I can write a few equations in the cells of the spreadsheet, so that a timed button-pressing can be given when I input the target coordinates and those of the plate-solving result.

 

I know how to use the setting circles, so I won't be too far from my target after manually move the mount head. I'll still use the x10 speed to slowly slew to my target with the help of the the formulae in Excel.

 

I'll give it a try. Thank you so much!

 

Lu

Excellent - good luck.

 

I recently had to create a spreadsheet to do a file conversion task. The RA & Dec data came as HH MM SS.S etc. If found it easier to just have a separate column for each of HH, MM & SS.S. It made data entry quicker and the calculation easier too!

 

Edit: of course who needs 'seconds or arc' anyway!


Edited by astrokeith, 17 June 2021 - 08:26 AM.

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