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Platesolve position in Stellarium

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#1 Spidy

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Posted 03 December 2020 - 08:46 PM

O.K., so after a very frustrating start to last night's imaging session (my first "real" session) I want to know of the quickest and easiest way of determining where you're actually pointing to, VISUALLY in Stellarium, in the sky. So my question is, after you use NINA or whatever to plate solve, is there a way to display exactly where you're pointing to in Stellarium?

Currently I'm using the very slow method of uploading to Astrometry.net, but it's very difficult to get a feel as to exactly how far off polar aligned you are using their small images on the results page.



#2 sbradley07

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Posted 03 December 2020 - 09:10 PM

Are you connecting to your mount via ASCOM from Stellarium?  With Stellarium and NINA connected to your mount, plate-solved corrections by NINA will be reflected in Stellarium.



#3 Spidy

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Posted 03 December 2020 - 09:15 PM

Are you connecting to your mount via ASCOM from Stellarium?  With Stellarium and NINA connected to your mount, plate-solved corrections by NINA will be reflected in Stellarium.

I use the CPWI drivers.

 

What do you mean by plate solve corrections?

 

In NINA I plate solve and try and read the error offset etc. What I'd like to do is plate solve, and then be shown in Stellarium where I'm actually pointing. The end game is to know how far off polar aligned I am to correct the mount so that Sharpcap can plate solve and start guiding me in the adjustments required.



#4 sbradley07

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Posted 03 December 2020 - 09:27 PM

Plate-solving is generally used to center your mount on a target.  The process iterates until the target is centered by sending position corrections to your mount. 

 

Configure Stellarium to connect to your mount using the Telescope Control plugin.  With both NINA and Stellarium connected to your mount via ASCOM, whatever NINA is pointing to will show as a telescope position in Stellarium.  You don't even need to plate-solve.  Whatever coordinates the mount thinks it's pointing at will show in Stellarium.  



#5 Spidy

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Posted 03 December 2020 - 09:41 PM

Thanks Steve. I'll give that a go next clear night I get. In Melbourne, that could be a while.........

 

Edit: The reason I say plate solve is because this is an initial step to get me close enough to use Sharpcap's Polar Align feature to work. If you're out by more than 5 degrees, it doesn't solve. That's the problem I had last night. That's why I need to see where the mount is actually pointing, not where it thinks its pointing.


Edited by Spidy, 03 December 2020 - 09:48 PM.


#6 RazvanUnderStars

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Posted 03 December 2020 - 11:32 PM

Also, if for whatever reason Stellarium doesn't connect to the scope, just pay attention to the message from the plate solver that pops up in SharpCap after solving, it gives the coordinates of the image center. You can type them in Stellarium. Again, just as plan B.

 

In fact, you can test the connection between Stellarium and the mount while indoors. You'll notice an extra marker in the sky map, showing the position where the mount thinks it is. Of course, without alignment the position will be wrong but the point is to verify that you see that marker.



#7 Spidy

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Posted 03 December 2020 - 11:57 PM

Also, if for whatever reason Stellarium doesn't connect to the scope, just pay attention to the message from the plate solver that pops up in SharpCap after solving, it gives the coordinates of the image center. You can type them in Stellarium. Again, just as plan B.

 

In fact, you can test the connection between Stellarium and the mount while indoors. You'll notice an extra marker in the sky map, showing the position where the mount thinks it is. Of course, without alignment the position will be wrong but the point is to verify that you see that marker.

Thanks for the advice.

 

Quick question. Do you check Sync and re-centre target to get the position in Stellarium?



#8 RazvanUnderStars

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Posted 04 December 2020 - 12:22 AM

Not sure if I understood the question correctly, but I'll break down what's happening:

  • Stellarium simply reads the current position from the mount and displays it. It does this automatically while you're connected to the mount. Stellarium doesn't know anything about syncing or corrections, it just polls the mount frequently, asking it "where are you pointing?". Of course, the position reported by the mount is where the mount thinks it's pointing.
     
  • when you do the one-click "plate solve and center" in SharpCap, a few things happen:
    • SharpCap reads the current position from the mount (where you told it to go, as RA/Dec) and keeps it aside
    • SharpCap takes an image and passes it to the plate solver (as an optimization, together with the above position as a hint about the rough area where the plate solver should look)
    • the plate solver figures out where the image is centered and communicates the coordinates to SharpCap
    • SharpCap tells the mount to do what's called a "sync", giving it the coordinates provided by the plate solver. The mount's model is shifted so that its sky map coincides with the given coordinates. Note there's no movement yet.
    • Now that that mount knows correctly where it's pointing, SharpCap issues a slew command to the RA/Dec coordinates read from the mount in the first step. Then the mount moves.

 

I hope this sheds some light onto what happens behind the click. To tie it back to your question, Stellarium is not aware of anything happening with the mount's model and you don't have to do anything to get Stellarium to show the current position apart from, obviously, connecting it to the mount.


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#9 Spidy

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Posted 04 December 2020 - 02:03 AM

....... Of course, the position reported by the mount is where the mount thinks it's pointing...........

 

That*s exactly my point. Since what I want to do is set up my scope, tell CPWI to "Home" the mount and begin Polar aligning, I need to see where in Stellarium the scope is actually pointing.

 

  • So, I set up my mount, should be pointing roughly to the SCP
  • Take a snapshot for a plate solve
  • and then see where in Stellarium the scope is actually pointing, that is, how far off the SCP I actually am.

I want to do this before the mount slews as the purpose is to use it as an aid to show me how far off I am and which knobs I need to turn to get it close enough for Sharpcap to solve in it's polar alignment routine.My scope's field of view is very tight (0.81 X 0.54 degrees) and Sharpcap sometimes doesn't solve coz I'm just that little bit too much out.

 

Does that make sense?



#10 RazvanUnderStars

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Posted 04 December 2020 - 08:03 AM

Understood, then you can do the following:

 

  • Put the mount at the Home position and connect both Stellarium and SharpCap to the "CPWI mount" (which appears as an ASCOM driver). I used to have a CGX and used CPWI.
  • In SharpCap, look in the Scope Controls panel that appears. Do you see a position reported there? IIRC, when at home position and unaligned, they assume they are pointing to the celestial pole. Since you're roughly in the area, this can be a useful hint to the plate solver.
  • If the answer is yes:
    • Make sure that in Sharpcap's Settings/Plate Solving/Actions solving from Telescope controls, the value is "Sync mount only" (since you don't want to slew anywhere, just to correct the mount)
    • click on the Plate solve and center button in the Scope Controls panel. This should be very fast since the plate solve will be done in the vicinity of the current believed position.
    • the mount's position will be corrected and you should be able to see it in Stellarium
    • move the alt/az controls as needed then try a plate solve in SharpCap's PA. Hopefully one adjustment will be enough to bring you close enough, if not repeat as needed
    • at the very end, go back in Settings/Plate Solving/Actions solving from Telescope controls and put the value back to "Sync mount and re-center target" (since this is what you want normally)
       
  • If the answer is no:
    • then in SharpCap go in Tools / Plate Solve which will do a blind plate solving (similar to uploading the image to astrometry.net). It will take longer but it will tell you the coordinates of the center. BTW, the recommended plate solver nowadays is ASTAP, much faster than previous solutions. Its author is an active contributor here on CN.
    • in Stellarium, go to the coordinates shown by the plate solver. You'll have to type them as Stellarium doesn't talk to the plate solver, but rather to the mount.
    • move the alt/az controls as needed then try a plate solve in SharpCap's PA. Hopefully one adjustment will be enough to bring you close enough, if not repeat.
    • EDIT: I think it's also possible to save the image, load it independently in the plate solver, specify the approximate coordinates and then do a plate solve that's not blind. The solving part will be very fast, but there are those extra steps.

Edited by RazvanUnderStars, 04 December 2020 - 08:12 AM.


#11 Spidy

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Posted 04 December 2020 - 08:37 PM

Firstly, let me say thank you so much for your detailed response RazvanUnderStars. People like yourself who take the time out to help beginners like myself are very much appreciated and make the hobby a little less frustrating.

 

Alas, I started to assemble the scope last night and the clouds started rolling inbangbang.gif

 

I don't remember seeing the telescope controls in Sharpcap, but I might set up the scope inside to see what I can see confused1.gif

 

Otherwise, I have to wait for the next clear night, which is days awaymad.gif

 

Edit: Oh, and BTW, thanks for suggesting ASTAP,I do use it as default in NINA and Sharpcap. I only use Astrmetry.net to get those lovely little gifs on the results page which show me where I'm actually pointing, hence the whole purpose of this thread. Thanks again RazvanUnderStars. I'll let you know how I go.


Edited by Spidy, 04 December 2020 - 08:42 PM.


#12 RazvanUnderStars

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Posted 04 December 2020 - 08:50 PM

You're welcome. 

 

The scope controls only appear once you're connected to a mount and they are further down, so if you have a few sections expanded (like they typically are), it might even be below the screen's real estate. You may want to drag it upwards, you'd use it often. All this stuff you can test indoors - I learnt in time that the fewer things I need to change at night, the fewer frustrations.

 

Enjoy,

Razvan



#13 totoantibes

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Posted 16 June 2021 - 06:12 PM

With APT there is  feature that shows in Stellarium (or whatever the Planetarium you have configured) the exact frame calculated by the platesolving process. not just the pointing but also the frame size and Orientation. that is a really useful feature. YOu dont even have to sync the mount (although you could).

 

In fact i was hoping the same was available in nina as i saw there was an integration configuration in Nina for planetariums but i have not figured out yet if Nina would in fact send the results straight back to the planetarium




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