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Changing observation location vs Plane Wave (SGP PlateSolve)

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#1 claudioarchi

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Posted 14 June 2019 - 09:27 AM

Hi all, I’m new to astrophoto. From what I understand we need to set latitude and longitude inside the plane wave tool for Platesolve to work properly. As for now, it’s working fine and i"m able to Platesolve easily from my backyard. But I’ll be going to a dark sky area that for sure will change my coordinates. Do I need to change latitude and longitude on the Plane Wave parameters?

Thank you all for your advice

 

I also posted this question on MainSequence Software forum:

http://forum.mainseq...lane-wave/10018

 

 

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  • Annotation 2019-06-14 101420.jpg


#2 han59

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Posted 15 June 2019 - 01:13 AM

In plate solving they could only be used to correct for a really tiny atmospheric refraction near the horizon. Other solver programs don't include them since the effect is in practice not noticeable for solving. So the stars in the south part of the image could be a little warped compared with stars in the north part of the image. There is no need to update the location.

 

Same for the catalog epoch. Changing the epoch doesn't influence the solve result measurable.



#3 OldManSky

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Posted 16 June 2019 - 03:35 PM

If SGP is connected to your mount (via ASCOM), it will send your lat/lon from your mount setup to the Platesolve software automatically.  You shouldn't ever have to enter it into Platesolve at all.  SGP (and NINA, which I use) do it for you.

Same with the "guess" RA/DEC coordinates for the solve.



#4 claudioarchi

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Posted 18 June 2019 - 09:08 PM

Thank you all for your answers is much clear now



#5 han59

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Posted 20 June 2019 - 01:09 AM

If SGP is connected to your mount (via ASCOM), it will send your lat/lon from your mount setup to the Platesolve software automatically. 

For the record, SGP executes PlateSolve2 only with the initial RA,DEC position and image dimensions as I described here. Analysing the SGP command line is easy by replacing the PlateSolve2 executable by an own program There is nothing in the command line referring to the users latitude longitude.

 

Experimenting with the latitude, longitude and epoch setting of PlateSolve2 (UCAC3) all result in the exact same astrometric (plate) solution. I can only guess these setting are either a dummies or help with compensating very tiny distortions. by atmospheric refraction and proper motion. In practice they can be ignored.

 

SGP uses PlateSolve2 v2.29 while from the PlaneWave website you can only download v2.28. The only difference is that version 2.29 writes always the .apm file solution using a point as decimal separator. V2.28 writes the .apm  solution with a comma or point decimal separator depending on the Windows local settings. Decoding the v.2.28 .apm solution file is problematic if the decimal separator is a comma since the values are also separated by a comma. For solving both versions behave the same.Change latitude or longitude has no detectable practical effect. If anybody finds one, I would be interested in their report.

 

Han



#6 han59

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Posted 20 June 2019 - 10:46 AM

This afternoon I played briefly with PlateSolve2 v2.29 and I think have an explanation. Using the program directly (C:\Users\your_user_name\AppData\Local\SequenceGenerator) you can press the button "Show image". At the PlateSolve2 image viewer status bar you see the Ra, Dec but also the Alt, Az of the cursor pointer. By playing with the location you can directly influence the indicated altitude. So my conclusion is that the "default location" is only used in the viewer. After changing the "default location" and initiate a new solve, the solution and X-, Y-distortion doesn't move a digit.

 

If you manipulate the observer altitude, you see a direct effect on the altitude indication. If you position the image very very close to the horizon you see that the altitude is 0.54 degrees higher then expected so the altitude indication is atmospheric refraction compensated.

 

--Han

 

PlateSolve2 image viewer:

platesolve2_viewer.png


Edited by han59, 20 June 2019 - 10:49 AM.



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