Starship Asterisk*

johnnydeep wrote: ↑Wed Jan 12, 2022 1:45 pm Thanks for the explanation. So in essence, PixInsight for the bulk of the processing, plus Starnet for the star removal effect.

cosmicwreckingball wrote: ↑Tue Jan 11, 2022 11:07 pm

johnnydeep wrote: ↑Tue Jan 11, 2022 9:57 pm So, Matt Harbison, how is this digital removal of stars done? Naively, I would think you would be left with "holes" where the stars were, but that's clearly not the case. Your before and after pics above show that a lot of the dimmer cloudy areas have also been removed or lessened in favor of showing more darkness.

Hi Johnnydeep,

Good question. Pixinsight- the calibration and integration software I use for my data is a powerhouse of mathematical equations and algorithms. However, in the case of StarNet The creator has written code (open source) for amateur astronomers to run on their master images to [and this is where I’m going to explain it as I understand it] take measurements of the surrounding background and simply calculate and replace the “holes”. This is done with a neural network to measure and calculate the missing data with the data in the surrounding backgrounds measured data. As for the muted light clouds, the software does diminish the highlights per the authors admission.

As mentioned above, by removing the stars and thus diminishing our pattern/recognition system, it provides a different view of the nebula and dust present. I understand it will not be for everyone and I make no claims to it’s ability to reproduce the exact missing data behind the star, I simply decided to display it this way as I felt it revealed structure that I had not noticed with normal exposures. I think it’s safe to say in the space of a star, not much is going to be added. I’ll also mention the data that I used starnet with is the Hydrogen alpha data (collected in early December this year) a very narrow band of information in the red spectrum. The overall brightness of the image with stars is blown out as I stated, simply because I didn’t pull a master to post.

Feel free to take a look at the calibrated data on my websites’s “Happy Holidays” blog post. Pixinsight has a 45-day free trial period as well. While not the most user friendly software, I find it wonderfully prepared to keep data as true to nature as possible.

johnnydeep wrote: ↑Tue Jan 11, 2022 9:57 pm So, Matt Harbison, how is this digital removal of stars done? Naively, I would think you would be left with "holes" where the stars were, but that's clearly not the case. Your before and after pics above show that a lot of the dimmer cloudy areas have also been removed or lessened in favor of showing more darkness.

Ann wrote: ↑Tue Jan 11, 2022 6:38 am

Sigma Orionis, the Horsehaed Nebula and various stars belonging to the Sigma Orionis cluster. Image: Lithopsian.

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Sigma Orionis is a multiple star and the central star of an entire very young cluster containing several pre-main sequence stars. The hottest, brightest component of Sigma Orionis is a star of spectral class O9.5 V, with a temperature of 35,000 K and a luminosity over 40,000 L_☉. Its close binary companion belongs to spectral class B0V, with a temperature of 31,000 K and a luminosity of 18,600 L_☉. Together, these two stars emit furious ultraviolet light that makes hydrogen glow red around them, and they provide the red background against which the Horsehead Nebula can be seen.

• (A good target for JWST, perhaps.)

https://en.wikipedia.org/wiki/Sigma_Orionis#Dust_wave wrote:

The Flame Nebula & σ Ori AB dust arc in infrared, with red representing 22 microns.

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<<In infrared images, a prominent ["dust wave"] arc is visible centred on σ Ori AB. It is about 50" away from the class O star, around 0.1 parsecs at its distance. It is directed towards IC434, the Horesehead Nebula, in line with the space motion of the star. The appearance is similar to a bowshock, but the type of radiation shows that it is not a bowshock. The observed infrared emission, peaking at around 45 microns, can be modeled by two approximately black-body components, one at 68K and one at 197 K. These are thought to be produced by two different sizes of dust grains.

The material of the arc is theorised to be produced by photoevaporation from the molecular cloud around the Horsehead Nebula. The dust becomes decoupled from the gas that carried it away from the molecular cloud by radiation pressure from the hot stars at the centre of the σ Ori cluster. The dust accumulates into a denser region that is heated and forms the visible infrared shape.

The term "dust wave" is applied when the dust piles up but the gas is largely unaffected, as opposed to a "bow wave" where both dust and gas are stopped. Dust waves occur when the interstellar medium is sufficiently dense and the stellar wind sufficiently weak that the dust stand-off distance is larger than the stand-off distance of a bow shock. This would clearly be more likely for slow-moving stars, but slow-moving luminous stars may not have lifetimes long enough to produce a bow wave. Low luminosity late class O stars should commonly produce bow waves if this model is correct.>>

Ann wrote: ↑Tue Jan 11, 2022 4:10 pm

rstevenson wrote: ↑Tue Jan 11, 2022 2:51 pm

Chris Peterson wrote: ↑Tue Jan 11, 2022 2:14 pm

It doesn't do anything for me. But I'm fine with APOD exploring different imaging and visualization techniques.

It does seem to be popular over on Facebook. But I most appreciate APODs when they teach, which this one does not.

Rob

As I wrote in my comment at top, we do see more of the red nebulosity surrounding Sigma Orionis in the APOD than we do in most traditional images. We also see some obvious blue reflection nebulosity near Alnilam, which is also rarely seen. So I don't agree that this APOD doesn't show us anything that we didn't know before.

But I am uncertain as to whether it was necessary to remove the stars in order to bring out the faint nebulosity.

Ann

Cameras, Binoculars, Dobs, Cats, and Refractors. Whatever it takes!

rstevenson wrote: ↑Tue Jan 11, 2022 2:51 pm

Chris Peterson wrote: ↑Tue Jan 11, 2022 2:14 pm

rstevenson wrote: ↑Tue Jan 11, 2022 11:28 am This is a rare case of an APOD I dislike. Removing the stars leaves an image of roiling gas and dust with no apparent reason to roil! The stars give meaning to the mass of gas and dust as well as to their colour. Without the stars this is just random brush strokes.

It doesn't do anything for me. But I'm fine with APOD exploring different imaging and visualization techniques.

It does seem to be popular over on Facebook. But I most appreciate APODs when they teach, which this one does not.

Rob

Chris Peterson wrote: ↑Tue Jan 11, 2022 2:53 pm

rstevenson wrote: ↑Tue Jan 11, 2022 2:51 pm

Chris Peterson wrote: ↑Tue Jan 11, 2022 2:14 pm
I'm fine with APOD exploring different imaging and visualization techniques.

I most appreciate APODs when they teach, which this one does not.

I'm not sure that's true. Certainly, removing the stars changes how our innate pattern recognition system operates. I definitely see the shape of the gas and dust structures differently without the stars. I'd call that a kind of "teaching".

rstevenson wrote: ↑Tue Jan 11, 2022 2:51 pm

Chris Peterson wrote: ↑Tue Jan 11, 2022 2:14 pm

rstevenson wrote: ↑Tue Jan 11, 2022 11:28 am This is a rare case of an APOD I dislike. Removing the stars leaves an image of roiling gas and dust with no apparent reason to roil! The stars give meaning to the mass of gas and dust as well as to their colour. Without the stars this is just random brush strokes.

It doesn't do anything for me. But I'm fine with APOD exploring different imaging and visualization techniques.

It does seem to be popular over on Facebook. But I most appreciate APODs when they teach, which this one does not.

Chris Peterson wrote: ↑Tue Jan 11, 2022 2:14 pm

rstevenson wrote: ↑Tue Jan 11, 2022 11:28 am This is a rare case of an APOD I dislike. Removing the stars leaves an image of roiling gas and dust with no apparent reason to roil! The stars give meaning to the mass of gas and dust as well as to their colour. Without the stars this is just random brush strokes.

It doesn't do anything for me. But I'm fine with APOD exploring different imaging and visualization techniques.

rstevenson wrote: ↑Tue Jan 11, 2022 11:28 am This is a rare case of an APOD I dislike. Removing the stars leaves an image of roiling gas and dust with no apparent reason to roil! The stars give meaning to the mass of gas and dust as well as to their colour. Without the stars this is just random brush strokes.