LinearFit between Ha and R images

[troypiggo]

I've read the description/announcement of the LinearFit tool, and I understand the use of it for images with similar filters but different exposures/optics maybe.  The M42 example makes it crystal clear there.

But what about Ha and R filters for example?  They could both be different exposures and binning.  The stars with the R filter will be brighter than the Ha, and conversely the nebulosity in the Ha will be stronger than the R.

I tried using the Ha as reference and applying it to the R, then tried the opposite with R as ref and applying to Ha.  The results were different.  And in both cases, when I applied the same STF to each image, they did not look the same.

What I'm trying to achieve is get either the stars similar brightness or the nebulosity similar, in order to combine/blend Ha with LRGB using Vicent's method.

Any tips/help?

[Juan Conejero]

But what about Ha and R filters for example?

LinearFit works under the assumption that the differences between pixels with the same coordinates in both images can be reasonably well described by a straight line. This is the only condition. When this condition doesn't hold, the achieved result is not valid, not because LinearFit fails, but because the problem is a nonlinear one.

In the case of Ha and R I think there should be no major problems, but it depends on the images. If you upload them we can make some tests.

They could both be different exposures and binning

Exposure differences shouldn't pose any problem, since the sensor's response is linear. If the images have different sizes, this will already be fixed in the previous---and necessary---image registration step.

I tried using the Ha as reference and applying it to the R, then tried the opposite with R as ref and applying to Ha.  The results were different.

This should not happen. Could you upload the images so we can get them a try?

[troypiggo]

Thanks Juan.  I've posted the Ha and the R channel extracted from RGB on Endor.  I think I did it logically.  30MB FITS files.

The Ha is 1x1bin 25x4min exposures and the R is binned 2x2 15x30sec exposures.  The G and B were same as R.  I also have Luminance that were 1x1 15x2mins.  I can provide the L, G, and B if you like.

Ha: http://endor.uv.es//data/public/fb169e49b91f47cf5b2fb3ff1aca8acd.php?lang=en
R: http://endor.uv.es//data/public/04574c0a292327c3e4d7513cb6280c6a.php?lang=en