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Alignment, Polar Alingment, Plate Solving ?

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#1 Astrosid

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Posted 19 September 2020 - 01:07 PM

As a newbie in AP, I am confused in setting up EQ mount for observation/imaging  
For example: Celestron scope Cgem/CGX mount

1.   Align by choosing multiple stars and calibrating.  Allows “Goto” via HC, Wi-Fi or USB connection via skyportal/SkySafari/Stellarium/ EQmod/etc for visual observation.   Will not provide accurate tracking for imaging.

 

2.  Polar align to accurately track for imaging after calibrating in #1 (Celestron All Star Polar Align)

 

3.  Plate solve after #1 and #2 for extremely accurate location of object. Critical for returning to exact location for multiple night imaging. 

4.  Or can you simply

      a. skip step #1
      b. visually align mount to Polaris,

      c.  Polar align (using Polestar for example),

      d.  plate solve (PS2,etc) 

Will this provide accurate Goto/tracking for imaging?

 

Polar alignment will provide accurate rotation of the RA axis - correct?

Plate solve will accurately define location (Goto) on RA axis - Correct?

Isn’t that all I need for imaging?  

 

 

 



#2 Dynan

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Posted 19 September 2020 - 01:22 PM

For a small investment, SharpCap at ≈$12/yr can take care of polar alignment among other great tools. It uses your imaging camera to polar align if you can see within a couple degrees of the NCP.

 

This plus guiding will be necessary for imaging unless you get into high dollar mounts.

 

Plate solving will find your target, but can be slow, depending on the program you use to plate solve.

 

So:

 

1) Polar align

2) Alignment (1, 2, or 3 points) this will give you your goto's

3) Plate solving after an aligned slew can be much faster at centering your target.

4) Guiding will probably be needed for longer exposures (PHD2, etc.)


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#3 kathyastro

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Posted 19 September 2020 - 01:29 PM

The alignment in #1 sets the electronics up to do the ASPA (#2).  However, ASPA (or any polar alignment technique) destroys the alignment from #1.  You should repeat that alignment after polar aligning, so that gotos are fairly accurate.

 

Having a good goto alignment will make plate solving much faster.  Plate solving will end up accurate regardless, but its first guess will be closer if the goto is aligned, requiring fewer re-tries to get it right.

 

In #4, again, you should do a goto alignment between 4c and 4d, for the same reason.



#4 sg6

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Posted 19 September 2020 - 01:39 PM

Not really going to anser the questions: However if it were as simple as that then imaging would be in effect "easy". It is anything but "easy".

 

Good polar alignment say 30 minutes and a lot of concentration. And that also means several months good experience. And rather simply people cannot be bothered to spend the time or effort.

 

You shouldn't need plate solving. You should be able to get the target the follow night, or some other night.

 

The 2 or 3 star alignment is for the Goto, and the goto is what movement has to be made for the scope to get from where I am to where I am now wanted to be. I am not 100% sure that it will correct for incorrect PA. The software could simply drop the Dec axis motor control and so track in RA only. People will say it shouldn't but unless I see the source code I would not guatantee it.

 

There is in effect one reasonable way to do this and that is learn it and do it yourself. After that a chunk of software might help but to an extent if you know how to perform it yourself you will have a much better understanding of what the software is trying to do.



#5 michael8554

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Posted 19 September 2020 - 05:53 PM

"Polar alignment will provide accurate rotation of the RA axis - correct?"

 

To be picky, PA minimises Dec drift. If Dec drift is minimised, then RA will better follow the apparent star movement across the sky.

 

"Plate solve will accurately define location (Goto) on RA axis - Correct?"

 

Plate Solve will accurately define RA and Dec location.

 

Setup sequence should start with Polar Aligning with the mechanical Az and Alt adjustments on the mount.

 

That will define how well the mount tracks stars.

 

Then Star Alignment by centring stars using slew commands only.

 

That will define how good the mount GoTos are.

 

If you Star Align first, then PA, you will have to Star Align again.



#6 bobzeq25

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Posted 19 September 2020 - 06:49 PM

As a newbie in AP, I am confused in setting up EQ mount for observation/imaging  
For example: Celestron scope Cgem/CGX mount

1.   Align by choosing multiple stars and calibrating.  Allows “Goto” via HC, Wi-Fi or USB connection via skyportal/SkySafari/Stellarium/ EQmod/etc for visual observation.   Will not provide accurate tracking for imaging.

 

2.  Polar align to accurately track for imaging after calibrating in #1 (Celestron All Star Polar Align)

 

3.  Plate solve after #1 and #2 for extremely accurate location of object. Critical for returning to exact location for multiple night imaging. 

4.  Or can you simply

      a. skip step #1
      b. visually align mount to Polaris,

      c.  Polar align (using Polestar for example),

      d.  plate solve (PS2,etc) 

Will this provide accurate Goto/tracking for imaging?

 

Polar alignment will provide accurate rotation of the RA axis - correct?

Plate solve will accurately define location (Goto) on RA axis - Correct?

Isn’t that all I need for imaging?  

It's all I do.  PoleMaster for polar alignment.  Use GOTO with no star alignment to get close, then platesoving to get exact.  I don't care how good or bad the GOTO is, the target need not even be in the initial field.

 

Very happy to leave the old days behind.  Messing around with polar scopes and star alignments.  Drift for polar.  This is _so_ much easier and faster.


Edited by bobzeq25, 19 September 2020 - 06:51 PM.

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#7 don314

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Posted 19 September 2020 - 09:11 PM

I'm doing the same as bobzeq25, only I switched to Sharpcap from polemaster for PA.


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