Stacking two stacks using Star Alignment

[umasscrew39]

Hi

I have 2 sets of stacked frames that I am trying to align to obtain one stack to work with.  I used one as the reference (15 stacked frames) but added both it and the other stack (20 frames) to Target Image list.  I tried doing this both in View and File option and got the same result.  That is, one final image that appeared to be aligned with a corner black area that you would expect if the camera, for example, was tuned from one night to the next.  However, the final image says 15 registered frames.  Should it not say 35 registered frames since I am stacking two stacks of 15 + 20?

Once that is resolved, then I assume I need to use image integration- correct? Or is that for only when I have more than 2 frames or stacks?

Bruce

[John_Gill]

Hi, firstly are you making a mosaic or do you want to combine image from multiple nights and is this OSC or filter images?  I assume you want to combine OSC from multiple nights. So I would Calibrate each stack, then do a CosmeticCorrection per stack and then Debayer all images. Next use SubFrameSelector for all images to select the best/reference image. Now, StarAlignment on all images/stacks.  Lastly ImageIntegration whatever passed the StarAlignment, and/or DrizzleIntegration.  You can end-up with an image with big black areas on the edges, mostly caused by field/image rotation. Crop it out and you are done... hope this helps

space is not black
John

[umasscrew39]

Thanks, John.  That helps and basically what I have been doing but still do not understand why at the top of the aligned frames that it does not indicate that all or most have been aligned.  Instead, it may say 12 of 80 frames aligned.  So, does hat mean the others have been dropped due to non-alignment?  If yes, why is that?  The stacks were taken the same night and each stack looks very good when processed alone and when I stack the stacks using SA, you can tell they aligned with some black along the edges due to movement.

[John_Gill]

Hi,

The Process Console will report  the number of images that align and which ones got rejected.

The StarAlignment process has been tightened up to align the stars at a sub-pixel level.  Your stars might be a little out of focus or might be a bit elongated - that causes a problem.  I normally try changing the Star Detection ---> Log sensitivity 1.0 and Noise reduction 2 or 3 and see how many image align.  If more images align then keep reducing the noise reduction until you run into trouble.

If this works, go back to "Blink" and take a careful look at the star sizes and shapes.  Also go thru SubFrameSelector and see if you should reject any bad images.  Run the StarAlignmet again with the default settings and see you can create a stack of good images.  Most times it is better to reject slightly bad images, but this depends on how many images you have.

space is not black
John

[umasscrew39]

ahhh.... got it.  Thanks much again for the explanation and suggestions.

Bruce