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sync difference between maximdl and sequence


tbaehnck

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Hi Group,

 

could anybody explain me what makes the difference between the two sync methods?

 

When I uses maximdl and make a sync with platesolving (target coordinates  are on JNow) and after taht I switch to sequence and made there a sync, I always have a difference.

Is this caused by different epochs in sollving the image or something else?

In maximdl I always use epoch JNow.

 

Its not a problem because pointing an d tracking are working very well but I like to know whats going on there.

 

Thanks and kind regards

Thomas

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The only thing I can contribute: I can confirm your observation.

 

May be a little off topic:

I investigated this phenomenom with respect to unguided tracking using MLPT...in one attempt I connected via MaximDL to TSX, in the other I connected via MaximDL to "Astrooptik Server Telescope" to receive the initial coordinates for MLPT plate solving in Sequence - result: no difference in tracking accuracy. I also tested different star catalogues as a basis for plate solving - no difference...

 

Unfortunately the weather in southern Germany does not allow additional activities to investigate the underlying difference...in the morning perfectly clear, in the evening clouds are rolling in...

 

Best,

Christian

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  • 1 year later...

Hello Thomas,

 

your problem reminded me of a conversation I had with Philipp Keller in 2010 were I suspected, that tracking errors might have been related to either using different epochs in TheSky, Maxim, Autoslew and Sequence or by problems in the conversion.

Here's a reply that Philipp sent me:

"was ganz anderes, ich habe gerade festgestellt, daß MaximDL offensichtlich nicht richtig Current Epoch in 2000 umrechnet.
wenn ich in Autoslew 9h, 50 Grad anpositioniere stimmen die Lokal-Koordinaten und Epoch2000 100% mit TheSky überein.
MaximDL hat die gleichen JNow, aber 11Bogensekunden Differenz in J2000. Ergo rechnet Maxim anders in 2000 um als ich und TheSky.
Das kann natürlich Auswirkungen auf Plate Solves haben. Ich muss der Sache weiter nachgehen.
Man sollte jedenfalls keine Differenzen bei MaximDL Platesolves verwenden.
Verwende ich den Sequencer umgehe ich das Problem vermutlich dadurch, daß ich selber in Epoch2000 umrechne und PinPoint solven lasse uns dann meine und Pinpoints Epoch2000 vergleiche. Sofern Pinpoint und ich die gleiche Auffassung von Epoch2000 haben sollte es also richtig sein."

 

Basically Philipp indicates that the coordinates in J2000 and Jnow are identical in Autoslew and TheSky, Jnow is also identical in Maxim, but there is a deviation in J2000 in Maxim compared to Autoslew and TheSky.

 

So it might make sense to do some tests with different epoch settings. In my fits-files that were platesolved by PinPoint under MaximDL, the coordinates in the fits-header seem to be J2000.

 

Best regards,

 

Robert

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Hi Thomas,

 

I don't know what Sequence is using when syncing. we would have to ask Philipp. I'm not sure if there is another way to find out. I think that Philipp mentioned that he uses Jnow in all places but I have to scan through my emails to verify that.

 

clear skies,

 

Robert

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