My Atik 383L OSC/ SGPro-Mosaic / PixInsight Mystery

[RQKimball]

I am posting the same “mystery” on the Atik Forum, SGPro Forum and the PixInsight Forum hoping someone can solve what I think is an interesting problem.  I am also adding links to my images via Dropbox.

First, some background.  I’ve been using my Atik 383L OSC camera with Artemis capture software for more than two years.  Both have performed beautifully.  I have also been a PixInsight advocate and user for at least two years.  I understand how to use flats, darks and bias images to calibrate my lights.  I have done several mosaics with very few problem.  (I have always used BGGR in PixInsight as my debayer matrix.

Two weeks ago, downloaded Sequence Generator Pro (SGPro) which I think is absolutely amazing piece of software.  The integration of plate solving and image sequencing to a joy to behold.  I also bought the “mosaic” add-on to SGPro which again is fantastic. 

But after all this joy, I ran into a problem that has me completely stumped.  I took my first series of images of the Heart Nebula with SGPro and moved them into PixInsight for processing.  I debayered the images using BGGR as always, and to my surprise, I discovered a green Heart nebula.  I changed the matrix to GRBG and I was back to the hydrogen we all know and love.  This surprised me, but didn’t seem like a big problem.

Next, I tried out the mosaic add-on. It worked beautifully. Four, twenty minute subs of the Heart Nebula with nice even overlaps in both directions.  I immediately fired up PixInsight to debayer, register and combine the four panels into one image. Again to debayer the images I had to use the GRBG matrix.  When I started to combine the image using StarAlignment -> Register/Union - Mosaic. I got an matching intersection but the two halves of the combined image seemed to have a very different matrix/noise/brightness structure.  I am attaching links to the images. 

Why would images produced with the same camera but captured with different software (Artemis vs. SGPro) act so differently in PixInsight?  I noticed in the .fits header of an old image captured by Artemis the fields BAYOFFX=1, BAYOFFY=1.  Maybe that’s a clue.

Here are the four Heart Nebula images (.fits)

   https://www.dropbox.com/s/afdcju4ui2e4u5q/Heart-1frame1.fit?dl=0
   https://www.dropbox.com/s/0vkv5gpl7s7tm8g/Heart-2frame1.fit?dl=0
   https://www.dropbox.com/s/3iz2wl3g8i4m2t9/Heart-3frame1.fit?dl=0
   https://www.dropbox.com/s/wrmw6ru3vocya9d/Heart-4frame1.fit?dl=0

Here are Heart1 panel and Heart2 panel combined

   https://www.dropbox.com/s/83c4vdk83pnah28/Heart1%262.jpg?dl=0

Here are Heart 3 panel and Heart4 panel combined

   https://www.dropbox.com/s/h45qejs7cxt86hx/HEART_3%264.jpg?dl=0

Here is the full mosaic

   https://www.dropbox.com/s/oat8h4aaesfzmja/Mosaic.jpg?dl=0

Here is a close up of one of the intersections

   https://www.dropbox.com/s/sba4yb398ipgw4u/Intersection.jpg?dl=0

[chrisjbaileyuk]

Fits can be written with two co-ordinate origins (top left and bottom left). With a OSC camera it does matter which is which in regards to which debayer setting to use (this can be changed in PixInsights Format Explorer).

The DropBox posted images are single uncalibrated frames?

For seamless Mosaics I use the following workflow.

ImageSolver - to insert WCS co-ordinates into each mosaic pane
MosaicByCoordinates - to put each pane onto a common canvas
GradientMergeMosaic - to create the final mosaic.

I just did this with your frames 1 and 2 and the result is a seamless mosaic

Chris

[RQKimball]

Thank you for your solution.  I appreciate hearing from you.

Bob