Hello Tim,
ABE stands for
Automatic Background Extractor. It is an application developed by Carlos Milovic, a member of the core PixInsight Development Team. In its current form, ABE is a standalone command-line application based on our PCL (PixInsight Class Library) development framework. ABE's miniwebsite is here:
http://pleiades-astrophoto.com/pixinsight/abe/DBE stands for
Dynamic Background Extraction. It is a process pertaining to the standard set of processing tools in the PixInsight platform. It was first introduced with PixInsight LE 1.0.2, and has been recently reimplemented, with a large number of improvements, under the new PixInsight Standard platform. PixInsight Standard's downloads page is here:
http://pleiades-astrophoto.com/download/STD/Both ABE and DBE are aimed at the generation of mathematical models that represent the sky background on a deep sky image (although they can be used for many other applications, including non-astronomical). These models are known as
synthetic background models or
pseudo-flats. A synthetic background can be used to correct for uneven illumination, including both vignetting and sky gradients due to light pollution, moon, amp glows, etc.
As its name says, ABE does its work in a completely automatic fashion: you provide a source image, a number of parameters controlling ABE's behavior, and you get another image with the generated background model. That model can be applied to the original image by subtraction or division, depending on the type of uneven illumination problems to correct for. Additive phenomena like light pollution gradients should be corrected by subtraction. Multiplicative effects like vignetting should be fixed by a division, though in this case a correct image calibration (flats) is the correct procedure.
DBE is a dynamic PixInsight process. Dynamic processes allow a high degree of user interaction in the PixInsight graphical user interface. Basically, the user defines a number of samples over free sky background areas, and the DBE process builds a background model by three-dimensional interpolation of the sampled data. This is a very rough explanation; DBE is actually much more complex and versatile.
With respect to PixInsight LE, the new DBE implementation in PixInsight Standard, which is freely available in the public time-limited beta of the platform, is a complete rewrite from scratch, and is much more efficient and accurate. DBE models in PixInsight Standard correct for uneven illumination and automatically provide background neutralization (i.e, you get the three histogram peaks perfectly aligned). In fact, now DBE can be used for robust chromatic correction with images that don't require gradient removal.
ABE is a very accurate and efficient application. Its functionality will be available as a process in the PixInsight Standard platform. DBE is also extremely accurate and versatile. Besides the fact that ABE is automatic and DBE requires user interaction, ABE and DBE use different interpolation algorithms. ABE performs a linear least squares fit, and DBE uses 2-D surface splines, which are more adaptable. However, the new DBE in PixInsight Standard uses a sophisticated system based on statistical sample weights that also produces very robust background models.
ABE can outperform DBE in relatively simple cases, where there are many free background areas, because its interpolation scheme is very robust. However, DBE is preferred for difficult cases because nothing can beat the human brain to decide where to put samples into a rich field plenty of nebulae and milky way condensations.
When ABE is implemented as a PixInsight process, you'll be able to compare both tools within PixInsight's GUI. Hopefully this will happen quite soon.
Juan
