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Mosaic Stars Issue  

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(@endeavor384)
Molecular Cloud Customer
Joined: 1 year ago
Posts: 3
December 6, 2020 19:41  

Hello - I'm doing a 4-panel mosaic and having an issue with the overlapping stars. They're not properly aligning and creating double stars. I've done about 5 mosaics now and the last two have experienced this despite the same settings. Not sure what to really try changing to correct this one. 

 

Settings:

Tab 0: no changes

Tab 1: loaded lights, and existing master files: flats, darks, dark flats, badpixelmap

Tab 2: no changes

Tab 3: default @ 500 which is ballpark estimate what i'd guess to be involved in the overlap

Tab 4: Default with Quads, 1 start 5 stop scale, rest default too

Tab 5: default with regular, multiple-scale, bwmv, scale 1.0 and lanczos-3

Tab 6: Average, quality, checkmark for local normalization, filter = sigma rejection, kappa low = 6, kappa high = 3, 1st degree LNC 1 iteration, 10% MBB

 

Other than messing with the stars on Tab 3 I'm not sure what will help the algorithms better analyze and align the stars.

 

Not sure what other information would be helpful  other than the double stars are ONLY between panels 1 and 3 (side by side on top) and the stars are identical, just one with a slight gap until the other. As it moves way from the center of the 60% overlap area that I'm doing they improve until they align properly. 

 

Mark Carter

double stars

 


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(@wvreeven)
Galaxy Admin
Joined: 3 years ago
Posts: 939
December 6, 2020 20:24  

Hi Mark,

in tab 3 up the number of stars to 2500

in tab 4 use triangles

in tab 5 switch to advanced.

Let us know if that works. 

Wouter


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(@endeavor384)
Molecular Cloud Customer
Joined: 1 year ago
Posts: 3
December 6, 2020 20:55  

@wvreeven gave that a shot, pretty much same results with the rest of the settings the same. I did double check the individual frames too to make sure I just didn't have a bad one I missed possibly but in the individual frames, stars look fine. Below is the image of panels 1 and 3 not aligning well, but then where panels 1 and 2 overlap perfectly fine.

good overlap

 

double stars

 


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(@endeavor384)
Molecular Cloud Customer
Joined: 1 year ago
Posts: 3
December 6, 2020 21:02  

@wvreeven 

 

To shed light on my process as well, I'm using NINA with 60% mosaic overlap just to ensure there' plenty of alignment points as I had issues with anything less than 40% and I've done a few now with 50% and 60% overlap but for some reason my last mosaic had this similar issue on 2 of the overlaps but since I reduced stars so much you couldn't even notice it, but this one I didn't plan to do much star reduction and it will be very apparent.

 

I am using a newtonian reflector and ensuring that the camera sensor of my asi1600mm is as close as possible to the same degree angle as the other 2 panels. Nina manual rotator wont image until I'm within like 1 degree and I believe between these two frames there was bout .2 degrees difference since I do have to remove the camera to collimate it and it's nearly impossible to get the exact same camera angle when realigning. But I am planning to finish the 4th panel tonight and hopefully won't have this issue on those 2 overlaps.


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3575
December 10, 2020 12:21  

60% is not needed, 10% is already plenty. So if that doesn't work, something else must be up. I would also change the scale start and stop; start to 5, stop to 10, read the tooltips of those settings by hovering over them with the mouse, they might give you some clues as well as how to set them. Also use dynamic distortion correction, that may also cause misalignment when it's off and needed because of your optics.


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