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2022-09-02: APP 2.0.0-beta4 has been released !

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Help! Im trying to combine three SHO channels, but one is slightly askew?


(@jay6879)
Brown Dwarf Customer
Joined: 2 months ago
Posts: 9
Topic starter  

I've been following this tutorial..

..I have split the Sulphur, Ha and Oxygen channels. I have three seperate files. Each file was made using the exact same data sets (two sessions worth), using the exact same settings, and yet the Ha channel is askew.

I've tried rotating it 1 degree and it appreas to be good, but when I use rgb combine it looks like a ghost image because the one channel doesn't line up. Everything is just slightly off.

What would cause one channel to not be aligned with thr other two despite containing the same data and processed using the same settings?

I'm kind of at my wits end here. I'd appreciate any help, and I'm sure it's something stupidly easy I'm missing..

 

Bizarrely I'm not allowed to upload FITS files here (?), so here is my Dropbox containing the files, can someone have a look at it please and see what the deal is? 

https://www.dropbox.com/sh/19z25u7xvbbaav2/AAA1yqpyeWtWaJwSKUUownCIa?dl=0


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(@jay6879)
Brown Dwarf Customer
Joined: 2 months ago
Posts: 9
Topic starter  

I forgot to add that when I take the three channels and try to combine them it says they aren't the same size and it doesn't work. So when I do a batch crop it WILL allow rgb combine to work, but obviously cropping doesn't align the three channels. The Ha channel is still askew.

Is there a way to align everything before I do a batch crop and rgb combine?


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1881
 

@jay6879 Hi,

Just load the integration results as lights (no calibration data), go to tab 4 and register them against each other. That will make APP align the images and give them the same dimensions. You can then save the registered frames at the bottom of tab 4 and load those into combine rgb. 

HTH, Wouter


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(@jay6879)
Brown Dwarf Customer
Joined: 2 months ago
Posts: 9
Topic starter  

@wvreeven 

So I would load Ha, OIII and Sulphur as Session 1,2,3 accordingly as lights, and juat register them?

Ok! I'll give that a go tonight, I've spent quite a bit of time trying to figure this out and if this works woo there will be another tool added to my knowledge of APP. I can use this going forward when combining any set of data, just make sure to register them so they are aligned and sized properly. I appreciate the help, I'll let you know how it goes!


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1881
 

@jay6879 No need to load them in separate sessions. Just assign them to the correct filters in one session and you should be good.


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1881
 
Posted by: @jay6879

Bizarrely I'm not allowed to upload FITS files here (?), so here is my Dropbox containing the files, can someone have a look at it please and see what the deal is? 

Sorry for the late reply to this. To the top of every forum page there are upload instructions. We don't allow large uploads to the forum and we have a separate file server for that.

Having said that, I have downloaded your files and will have a look. Do the ones you made available contains the file that you rotated manually?


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(@jay6879)
Brown Dwarf Customer
Joined: 2 months ago
Posts: 9
Topic starter  

@wvreeven 

No, these files are not rotated. They are just the integrations for each channel. 

Edit- I'm not sure how I missed those upload instructions, makes sense now that I think about it!

This post was modified 1 month ago by Jay6879

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(@jay6879)
Brown Dwarf Customer
Joined: 2 months ago
Posts: 9
Topic starter  

@wvreeven 

That did it! Much appreciated. I followed the video and my colors didn't look anything like his, mine were very muted, but that's something I'm sure I can figure out messing with sliders.


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1881
 
Posted by: @jay6879

..I have split the Sulphur, Ha and Oxygen channels. I have three seperate files. Each file was made using the exact same data sets (two sessions worth), using the exact same settings, and yet the Ha channel is askew.

I had a look at the files that you uploaded. I think a meridian flip was involved when imaging. APP probably selected a light that was taken after the flip as reference and that resulted in an image that is rotated 180º wrt the OIII and SII images. Other than that I see no obvious differences.


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(@jay6879)
Brown Dwarf Customer
Joined: 2 months ago
Posts: 9
Topic starter  

@wvreeven 

Ahhh that makes sense. Is there a way to set what APP uses as the reference frame?

Regardless, it's good to know that you can register the images again and they'll be aligned nicely.

 


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1881
 
Posted by: @jay6879

Is there a way to set what APP uses as the reference frame?

Yes there is. After loading the images, go to tab 3 and click "analyse stars". When it is done, go to tab 4 and select the file you want to be reference in the file list. Right click and select "set as reference" et voila!

Why would you want to do this? APP has very good internal algorithms to select the best frame as reference. In general you should not need to do this manually.


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