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Stellarium inaccuracies

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#1 Simon Dunsmore

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Posted 26 January 2021 - 02:20 AM

Hi Folks,

So, after spending the last couple of cloudy weekends setting up my mount to work with Stellarium, I finally got a break in the clouds last night and decided to try it for real.

Everything seemed to work well apart from the accuracy. The scope slewed to near the target but not to it. I realigned the star into the eyepiece and used ctrl 3 to sync it with stellarium several times but still not accurate.

Before I started I used a polemaster to polar align. I was wondering, when Stellarium starts up it shows the scope centred on polaris, but actually it's the mount that is centred and not the scope. Does this mean that once I'm polar aligned that I need to put polaris in the eyepiece before using stellarium or are my inaccuracies down to something else or both?

Thanks for your help

Simon

#2 Jim Davis

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Posted 26 January 2021 - 03:47 AM

Stellarium gets its pointing information from the mount. It has no idea otherwise where the scope is pointing.

 

Ctrl + number determines which telescope you are controlling. You can control multiple telescopes at one time. Ctrl-3 would control scope number 3.

 

The StellariumScope add on has the ability to sync the software and position the mount is pointing.


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#3 Simon Dunsmore

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Posted 26 January 2021 - 04:27 AM

Hi Jim, thanks for the reply. Yes, I have stellarium scope installed. This is what I meant with regards to the ctrl3 comment. Sorry, should have mentioned this.

#4 barbarosa

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Posted 26 January 2021 - 06:11 AM

You may not need to use Stellarium Scope. Recent versions of Stellarium can use ASCOM for mount control. It works very well for my CEM60. 

 

If you have a good PA and Stellarium points the mount incorrectly it could be that you have an error in the data entered for location or the time is off(system time is not always correct or the mount might be using a different clock), or the coordinate system is wrong for the mount (J200 vs  Equinox of date/J Now).


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#5 Jim Davis

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Posted 26 January 2021 - 07:47 AM

Hi Jim, thanks for the reply. Yes, I have stellarium scope installed. This is what I meant with regards to the ctrl3 comment. Sorry, should have mentioned this.

Make sure you have the stellarium scope panel in focus, i.e. the current program on top.



#6 Simon Dunsmore

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Posted 26 January 2021 - 08:14 AM

Thanks Jim, will do. Can I ask what your thoughts are on the start up position after polar alignment. Should I align polaris in the eyepiece after polar alignment with polemaster?

#7 Simon Dunsmore

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Posted 26 January 2021 - 08:14 AM

Thanks Jim, will do. Can I ask what your thoughts are on the start up position after polar alignment. Should I align polaris in the eyepiece after polar alignment with polemaster?

#8 Jim Davis

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Posted 26 January 2021 - 08:20 AM

Thanks Jim, will do. Can I ask what your thoughts are on the start up position after polar alignment. Should I align polaris in the eyepiece after polar alignment with polemaster?

What mount are you using?



#9 Simon Dunsmore

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Posted 26 January 2021 - 08:22 AM

Skywatcher Heq5 pro goto

#10 Simon Dunsmore

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Posted 26 January 2021 - 08:22 AM

Skywatcher heq5 pro goto mount

#11 Jim Davis

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Posted 26 January 2021 - 08:26 AM

I wouldn't think that would be necessary. The polemaster should have the mount properly aligned.



#12 daw316

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Posted 26 January 2021 - 11:30 AM

To back up, can you say why you need StellariumScope?  My ASCOM synch's fine without it.


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#13 Simon Dunsmore

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Posted 26 January 2021 - 01:04 PM

Hi, without stellarium scope I seemed to have lost the cntrl 3 sync option

#14 SkipW

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Posted 26 January 2021 - 05:22 PM

Do you have the correct coordinate system selected?

 

Celestron mounts work with Equinox of the date (JNow) but Stellarium defaults to J2000. These are different by about a quarter degree in some parts of the sky now (worst on the ecliptic). I'm not sure which one SkyWatcher expects, but it's something to check.

 

If the mount's own pointing is accurate but Stellarium is off by a bit, this could be the cause. I have found that letting Stellarium point the telescope using ASCOM is quite accurate if using coordinates for the right epoch.




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