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Simple Plate Solving question

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#1 Stelios

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Posted 21 April 2017 - 01:05 PM

I'm about to spend the evening getting plate-solving going (I've tried before unsuccessfully) with SGP Pro.

 

My question is simple: Assuming plate solvers (and blind fail over) are set up correctly: Can I plate solve by simply supplying the RA/DEC coordinates of the object I want to center on? Or do I *need* to supply an image to get the whole thing going? 

 

Of course telescope/camera will be connected via ASCOM and appropriate driver.


Edited by Stelios, 21 April 2017 - 01:06 PM.


#2 ismosi

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Posted 21 April 2017 - 01:17 PM

Astrometric solutions ('plate solving') require an image, otherwise, what would you be comparing?

 

In my automated imaging setup, I enter the RA/Dec of the target I want to image. Telescope slews to those coordinates. Image is taken, then the astrometric solution RA/Dec is compared to where my telescope 'thinks' it's pointing.

 

If it's not, synch/recal on the actual coordinates and re-slew. Repeat until within set error.

 

Does this help?


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#3 Alex McConahay

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Posted 21 April 2017 - 01:27 PM

Stelios

 

You may not have asked the right question.

 

Plate Solving is, by definition, something done to a picture.

 

However, I see you are using Sequence Generator Pro. If you are trying SGP for the plate solve, you do not need a picture before starting your session. You can tell SGP to slew the scope to wherever you want (by telling it the RA and Dec.) That does not require an image. SGP will do what is necessary to move the scope to the target area, and take a picture. It then PLATE SOLVES that picture to determine where it is. If it is where it belongs, fine. If it is not, it figures where it is, and moves again to where it should be, takes another picture, and Plate Solves again, and again, until it is in the right place, or runs out of tries (which you have specified.)

 

Before trying the slewing and Plate Solving, though, you should be reasonably well polar aligned, and your mount should be able to do a goto all by itself. If it cannot do that, then SGP will not be able to do it for you. (In addition, have your scale set before trying this if at all possible. )

 

Alex


Edited by Alex McConahay, 21 April 2017 - 03:08 PM.

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#4 S.Boerner

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Posted 21 April 2017 - 01:44 PM

I do find that SGP's plate solving is VERY dependent on the arcsec/pixel of your setup (press ctrl-E then camera tab and look for scale.)  If you are at all unsure about it or if your attempted solves don't work, consider going to astrometry.net and have them do one for you

(http://nova.astrometry.net/upload)  and use that value.



#5 anismo

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Posted 21 April 2017 - 01:48 PM

Also, Platesolve2 is much better than Elbrus . So it is worth setting it up. As mentioned earlier, The camera image scale information is very important for successful solves (I just take an image 1x1 and save it and upload the STF stretched version to astrobin (or astrometry.net) to get the arcsec/pix number). 


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#6 Ladyhawke

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Posted 21 April 2017 - 01:52 PM

If you are using SGP you can slew to an area of the sky that you want to image, center your target and Plate Solve. After doing this you can save the profile and when you need to go back, it will go exactly to the same location where you were before when you plate solved.


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#7 Stelios

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Posted 21 April 2017 - 02:05 PM

Stelios

 

You may not have asked the right question.

 

Plate Solving is, but definition, something done to a picture.

 

However, I see you are using Sequence Generator Pro. If you are trying SGP for the plate solve, you do not need a picture before starting your session. You can tell SGP to slew the scope to wherever you want (by telling it the RA and Dec.) That does not require an image. SGP will do what is necessary to move the scope to the target area, and take a picture. It then PLATE SOLVES that picture to determine where it is. If it is where it belongs, fine. If it is not, it figures where it is, and moves again to where it should be, takes another picture, and Plate Solves again, and again, until it is in the right place, or runs out of tries (which you have specified.)

 

Before trying the slewing and Plate Solving, though, you should be reasonably well polar aligned, and your mount should be able to do a goto all by itself. If it cannot do that, then SGP will not be able to do it for you. (In addition, have your scale set before trying this if at all possible. )

 

Alex

You are correct, that's exactly the question I was *trying* to ask smile.gif, and how I'd like to operate: Set my target coordinates, slew and center there. 

 

I have all the other "pieces," so maybe this will finally work! (I think my other failures may have been due to my scale set in one place but not in another).



#8 Stelios

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Posted 21 April 2017 - 02:07 PM

Also, Platesolve2 is much better than Elbrus . So it is worth setting it up. As mentioned earlier, The camera image scale information is very important for successful solves (I just take an image 1x1 and save it and upload the STF stretched version to astrobin (or astrometry.net) to get the arcsec/pix number). 

I do have Platesolve2 and local astrometry.net as backup. I believe I have the correct camera image scale (1.48") for my Rebel T3i and ED80, but your idea for checking it is excellent, thanks!



#9 Becomart

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Posted 21 April 2017 - 03:02 PM

1.48 sounds about the right ball park. I have a canon 100d which is 1.85. You'll never look back after plate solving, it makes setup so much quicker. No more messing around with alignment stars. 



#10 Stelios

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Posted 22 April 2017 - 01:34 AM

And guess what, it all worked! Plate-solved M51 in about 2 seconds! Seeing the galaxy dead center after the "center" command--priceless!

 

Thanks to everyone, including Jared and the rest of the SGP group for making the code work, and to Alex for his excellent tutorial. bow.gif bow.gif


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#11 Becomart

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Posted 22 April 2017 - 02:12 AM

Witchcraft I tell you...it's witchcraft!




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