BlurXTerminator (BXT) is a deconvolution: it estimates how optics, seeing and tracking blurred the image and computes that blur out. Star shapes are corrected, stars become more compact and nebula structures sharper.
Purpose
Task
Setting
correct star shapes (aberrations, slight distortions)
Correct Only
make stars smaller
Sharpen Stars
reduce halos around stars
Adjust Star Halos
sharpen nebula structures
Sharpen Nonstellar
Principle
Deconvolution requires linear data. The point spread function (PSF) is determined from the stars.
Colour calibration should come first, so that its photometry measures unaltered star profiles.
Denoise afterwards: denoising destroys the PSF information BXT needs for the reconstruction.
BXT moves the stars of an image towards a compact, similar profile. Differences between exposures (seeing, focus, filter) become smaller but do not disappear entirely.
Parameters
Parameter
Effect
Typical choice
Correct Only
corrects star shape and aberrations only, without sharpening
as a first pass
Sharpen Stars
strength of star reduction
0.25–0.5
Adjust Star Halos
negative values reduce halos
0 to −0.1
Sharpen Nonstellar
sharpening of nebula structures
0.5–0.9 (strong channels such as Ha take more, colour images less)
Automatic PSF
determine the PSF diameter automatically
enabled
Operation
Apply to the linear image, after gradient correction.
First Correct Only, then a pass in normal mode.
With several images that will be combined later, process each image separately.
Typical applications
Several channels with matching star profiles
If images are later subtracted from one another or combined pixel by pixel (e.g. in a continuum subtraction Ha − q · R), stars must have the same size and profile in both.
Situation
Consequence in the difference
star wider in the subtracted image
too little subtracted at the centre, too much at the edge → bright core with dark ring
star narrower in the subtracted image
too much subtracted at the centre, light remains outside → bright ring, often with a black hole
matching profiles
stars largely disappear, nebula remains
Choose Sharpen Stars and Adjust Star Halos the same or very similar in both images.
Sharpen Nonstellar may differ – it only affects nebula structures.
Apply Correct Only to both if used for one.
If a channel is later extracted from a colour image, it inherits that image’s BXT treatment; the second image must be treated comparably.
What a good result looks like
Typical errors
Observation
Cause
Remedy
Worm-like patterns in the nebula
Sharpen Nonstellar too high for the noise
lower Sharpen Nonstellar
Dark rings around stars
Sharpen Stars or halos too strong
lower the values
Little effect
image already stretched
apply to the linear image
Rings or holes after continuum subtraction
star profiles differ between images
same star parameters in both
When to use it – and when not
Good for
Better another tool
sharpening linear data, correcting star shapes
shrinking stars in the stretched image → Makes stars smaller instead of merely dimming them – faint stars recede, bright ones remain as accents. Easiest in a separated star image.Open fundamentals →
before denoising
noise → AI-based noise reduction with separate strength for fine- and large-scale noise and for brightness and colour. Several light passes keep more detail than one strong pass.Open fundamentals → (afterwards)