Star Core Rings

[timtrice]

Please take a look at the attachment and advise. I'm unsure if this is a deconvolution artifact, masked stretching or MLT. I've been trying to pay attention to the star cores but apparently not well enough. In particular I'm looking at the blue star with pink/magenta core at 3195, 3156. I'm trying to repair with the HSV repair script but not having much luck.

[Alejandro Tombolini]

Hi, Deconvolution can easily generate it on big stars and then it will be increased by further processes. See this example and other, regarding Deconvolution and the use of mask to protect big stars during the process.
See also this example about reparation of saturated stars cores before of MaskedStrecht
Taking both precautions you should obtain a better result and if it still need a reparation you can use MLT with an inverted star mask as showed here or MorphologicalTransformation as describe in this example.
Saludos, Alejandro.

[timtrice]

Alejandro, thank you for your quick response. I have read over I think every one of those tutorials and find them of great benefit. Some seem to not have the same "steps" in order so I do find it confusing. I had been struggling for quite some time with HSV restoration but I may have finally gotten a grip on it.

Anyway, I've corrected the issue but over processed significantly so I'm going back and starting from scratch.

Thanks again!

[Alejandro Tombolini]

A general recommendation would be that after every process you have applied, inspect the stars. Specifically after Deconvolution deactivate the STF and see the stars. If the big ones were not protected with a starmask they will show that darker core.
Other tools can also generate something similar on stars if they are not protected, like HDRMultiescaleTransform on non linear postprocesing.

Some seem to not have the same "steps" in order so I do find it confusing.

Yes, the order and process applied in general depends on the need of the images

Saludos, Alejandro.

[jkmorse]

Tim,

Like Alejandro said, that looks like a decon artifact that just gets worse with further processing.  Here are tips for the decon deranging mask I picked up from others:

Local Support Deringing Mask:

As a first step try deconvolution without local deranging support.  For many images, global deranging alone may be sufficient.  If you need local deranging support, then build the deranging mask as follows:

Mask bright stars, but not just “super bright”
Look for strong red on bright stars, no protection on target

Pre-process image before applying StarMask
Duplicate image
Use MLT to remove 1st and residual wavelet layers in a 5 layer decomposition
Use StarMask on resulting image per below

Use Star Mask tool
Starting settings:
Noise threshold: 0.01
Scale: 3
Structure growth: 1-4-2
Smoothness: 16
Check “aggregate” and “binarize”
Do not check “invert”
If any of the target area remains (such as bright portions of galaxies), use CloneStamp tool to remove while leaving highlighted stars untouched
Smooth mask by applying a Gaussian Convolution
Start at settings of StdDev 5, Shape 2, and Aspect Ratio 1
Once satisfied, rename “Deringing mask”
Minimize for later use

It is VERY important to build a suitable local support for deringing: Try using a StarMask that covers well the brightest stars with 10-15 pixel of smoothness and truncation at about 0.75. Then fine trim deringing with a very small (usually less than 0.02) amount of global deringing.


Best,

Jim

[Daan]

HSV repaired separation doesn't do it for me. What does seem to work for me to avoid (or significantly reduce) pink star cores is to first do a HistogramTransformation stretch with a low background setting of e.g. 0.01 and than run Masked stretch. I can imagine that the result of first doing a gentle normal Histogram stretch is that the first mask being used at Masked Stretch becomes stronger?