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Topics - astroedo

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Tutorials and Processing Examples / Videotutorial on Comet processing
« on: 2018 September 12 15:17:30 »
Dear friends,
here my latest video tutorial on Comet processing.

Unfortunately it is only in Italian, but it is quite self-explicative, so, I hope, you can still enjoy it.

Best regards

Bug Reports / Radial Symmetries in DBE
« on: 2018 September 09 12:59:55 »
Hi PI Team,

I was experimenting with Symmetries on DBE and I've found a strange behavior on astronomical images, so I've tried with "synthetic" gradients.
It seems, when symmetries are used, that the resulting gradient is image size-ratio dependent.
As you can see on the attached images, i've created a symmetric circular gradient.
On a square image the resulting DBE gradient is circular.
With the same sample geometry, on a rectangular image, is elliptic.

Am I making something wrong or is it a BUG?

Thank you

Bug Reports / Problem with PhotometricColorCalibration
« on: 2018 August 26 04:59:53 »
Hi all,
I'm Trying to use PCC with an image of the Veil nebula.

I've used PCC before without problems and I know quite well the process, but now, with this image, it fails.
The procedure goes well almost to the end, but at the very end PI tells me

Photometry process finished:
   3 of 3 images processed successfully.
   0 images with errors.

*** Error: Insufficient photometric data: Got 0 sample(s); at least 5 are required.
Reading swap files...
1830.416 MiB/s
<* failed *>
I've tried with different servers and setting, but the problem seem to be only teh color calibration data in this area of the sky.

I cannot figure out why.

Thank you for any help.


General / Different Behaviour on HDTMT in preview and Image
« on: 2018 May 16 13:50:27 »
Hi all,

I'm processing an image of the M106 region.
It is a 2490x1882 image, a Halpha - RGB composition, taken by me (16 hours of Halpha) and a friend (3 hours of RGB with an OSC).

As a part of my processing workflow, I'was using HDRMultiscaleTransform to popup the details on the very center of M106 and, as usual, I've tried  the settings on a small preview around M106.

When found the best setting, I've applied the Process to the whole image but, with my great surprise, the result was VERY different from that on the preview, as you can easily see on the attached images.

The Image was non linear (HT + MS + Curves)
HDRMT setting was

6 Layers, 1 iteration, Median Transform active, Preserve Hue Active, Lightness Mask Active.
An additional, very blurred, Lightness mask was applied.

Even stranger, if I perform the very same operation, on the RGB image only, HDRMT performs as expected with no differences between preview and Image.


By the way, this is the final image

General / asking advice about ubuntu vs Windows 10 version
« on: 2017 August 19 08:31:57 »
Hi all,

I'm formatting and reinstalling my old notebook.

It is an ASUS notebook with a INTEL CORE DUO processor and 4 GB RAM + 1 GB Graphic RAM.
My main O.S. is Windows 10 64 Bit where PixInsight runs decently and I'm happy about it, but I was evaluating the idea of making a multiboot system with Ubuntu (or Xubuntu, Lubuntu that seems lighter for my old machine).

- Has someone tested Linux PI Version compared with windows version on the very same machine?
- Which system has better performances? (If one in better than the other)
- In your opinion, is my idea good or fool?
- Are there other Free Linux distributions more suitable for this job?

Thank you in advance for your help.


General / Linear "L" RGB Combination
« on: 2017 March 05 10:27:54 »
Hi All,

it is a bit of time that I'm trying to find a way to make an "L" RGB combination at linear stage.
We all know that the real LRGB combination must be done on NON linear images, matching the luminosity profile of the L image with the RGB one and combining in with the LRGBCombination Process (or Channel Combination); this because the CIE Lab color space is nonlinear, so we cannot use a linear L.

Googling on the internet I haven't found any solution, except an old post here on the forum

where Juan suggests a method to combine a linear L with RGB.
Unfortunately I haven't managed to make it work: on my images this method creates horrible Green and magenta artifacts (don't know if I'm doing something wrong).

So I've tried to find a solution by myself, and, maybe, I've found it.

This is my workflow:

I have 4 images: R G B and "L"

  • RGB combination with ChannelCombination
  • BackgroundNeutralization
  • ColorCalibration
  • Extract I Channel from HSI color space with ChannelExtraction
  • Use LinerFit on "L" using  I  as reference
  • Insert fitted "L" in RGB image with ChannelCombination (Use HSI color space deselect H and S checkboxes and use "L" as I )
Thats all folks!  :D

Processing the image the final result is practically Indistinguishable from a normal LRGB.
The I component of the HSI color space is a linear combination of RGB so it is linear and can be combined at linear stage.

We can call it IRGB Combination instead LRGB.  ;)

What do you think about this workflow?
Am I doing somthing wrong?



General / Using the transformation matrix of star alignment.
« on: 2016 August 25 03:46:59 »
Hello to all.

As you know, after the star alignment process, the transformation matrix for the align operation is shown in the process console.

Here my question: can I use this matrix to apply the very same transformation to another image?

For example I have Image A, image B and a starless copy of B (let's call it C)
I want to register C on A: I can register B on A and then I want to use the same transformation on C.
Is it possible to use the transformation matrix to replicate the same transformation from B to C?

If yes: HOW?

Thank you.

Hi all

During the Halloween week end I got some Narrow Band data on the Flaming Star Nebula.
Waiting for the OIII data I've tried a weird experiment: a false color composition of Ha and SII

Ha and SII emisson lines lays both in deep red so it is impossible to render color differences in a real way: the only option is a false color composition.

In this image Hydrogen emission has the usual pinkish color due to the Ha and Hbeta emission lines.

As said before the SII emission line lays in deep red, but on Earth the cristalline sulfur has yellow hues so my goal was to render the SII in yellow.

To accomplish My Goal I've used the PixelMath tool in PixInsigth.

The composition formula was:

R Channel: Ha
G Channel: SII
B Channel: 0.25*Ha - 0.75*SII
The B channel formula is very simple the 0.25*Ha acconts for the Hbeta emission giving to the Hydrogen emission the usual pinkish color, subtracting the SII emission shifts the color hue of the Sulfur rich zones toward yellow the 0.75 factor is an arbitrary value chosen to render the wanted color.

See also on my site

and Astrobin

Tutorials and Processing Examples / Playing with Drizzle
« on: 2015 August 30 02:43:41 »
Hi all!

I've finally managed to try the Drizzling feature of PI and I'm impressed of the result.
It produces a REAL increase in resolution.

Look here.

Not a very good image indeed, but a nice Drizzle example.

I've used it with the default settings.

The Astro Imaging Channel: Challenge nr 1

The Astroimaging Channel on Google+ proposed an image processing challenge (read here) based on a set of RGB images of the Markarian chain.

This was the challenge:

Gradient Removal while preserving star color.
A few months back, I wanted to try imaging my blue channel high up in the sky.  It didn't work out as planned and I have a terrible gradient through the image.  I've been able to get rid of the gradient, but it leaves a bad color cast through my stars.  The challenge is to remove the gradient and preserve the star color.

Here my solution in PixInsight.

Hi All here my latest tutorial: as from the subject it's about using an H alpha image to enhance HII regions in spiral galaxies.

The method is directly derived from Vicent Peris formula for composition of Narrow band data with broad band ones.

I how you will enjoy

Anche in italiano

Hi all,
I've just published on my website a new tutorial on narrowband composition.

It is an adaptation of original J-P Metsavainio technique.

I hope you enjoy it


Workshops and Conferences / Corso Base di PixInsight in italiano
« on: 2014 October 10 01:10:07 »
Hi all,
at the end of october 2014 will start a basic course of PixInsight at La Torre del Sole in Brembate (near Bergamo, Italy).
The course will be in Italian, so now I switch to my language  :D

Ciao a tutti i colleghi italiani.
A breve inizierà un corso di PixInsight in italiano in cinque lezioni presso la Torre del SOle di Brembate (BG).

Vi allego il programma del corso con tutti i dettagli per l'iscrizione.

Thank you

Workshops and Conferences / Introduzione a PixInsight in italiano
« on: 2014 September 17 12:11:38 »
Hi all, I'm sorry for the italian title, but this brief workshop will be in Italy and in italian: I will translate my post at the end  ;)

Venerdì 3 ottobre 2014 presso la Torre del Sole di Brembate di Sopra ( presenterò una breve lezione su PixInsight.
Sarà una introduzione a questa spettacolare piattaforma di image processing adatta a chi vuole avvicinarsi per la prima volta al programma.
Sarà però anche un'occasione per coloro che già usano PI per scambiarsi idee e proposte.

Vi allego il volantino dell'iniziativa.

On Friday, October 3rd, 2014 at la Torre del Sole in  Brembate di Sopra (  I will present a brief lesson on PixInsight.
It will be an introduction to this spectacular image processing platform suitable for those who want to approach for the first time the program.
However, it will also be an opportunity for those who already use the PI and wish to exchange ideas and proposals.

I am attaching the initiative leaflet (in italian).

Clear Skyes

Hi I've just published a simple processing workflow based on a picture from Goddchen M8 postprocessing contest.

It covers all the processing workflow in a simple way, good for beginners.

I hope you'll enjoy it

English version

Versione in italiano

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