APOD: Comet Nishimura Grows (2023 Sep 09)

[APOD Robot]

Comet Nishimura Grows

Explanation: Comet Nishimura is growing. More precisely, the tails C/2023 P1 (Nishimura) are growing as it nears the Sun. Discovered only last month, the comet is already near naked eye brightness as it now moves inside the Earth's orbit. The comet will be nearest the Earth next week, but nearest the Sun the week after -- on September 17. Speculation holds that expelled ice and dust from Comet Nishimura's last visit to the inner Solar System may have created the Sigma Hydrids meteor shower which peaks yearly in December. If so, then this meteor shower may become more active, refreshed with new comet debris. Pictured, Comet Nishimura was captured from Edgewood, New Mexico, USA four nights ago, showing a long ion tail structured by interactions with the Sun's wind. Look for this comet near your eastern horizon just before sunrise for the next few mornings, but very near your western horizon just after sunset next week -- as its coma continues to brighten and its tails continue to grow.

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[Knight of Clear Skies]

I was lucky enough to see Neowise from Bodmin Moor dark sky park in 2020 and made this timelapse (the annotations on the stacked image were inspired by an APOD):

https://youtube.com/shorts/iWtgyLQd8ik? ... rl9gh4qdw2

Unfortunately sounds like Nishiimura won't be nearly as bright and will be tricky to spot in the pre-dawn light. If you're getting up early to see it I'd recommend taking a pair of binoculars with you.

[Chris Peterson]

I've never seen a comet that changed its appearance so quickly. The solar wind and radiation is really tearing at it. These are from this morning and from yesterday morning, so just 24 hours of evolution. Images are 2 degrees wide.
_

[Christian G.]

I've never seen a comet that changed its appearance so quickly. The solar wind and radiation is really tearing at it. These are from this morning and from yesterday morning, so just 24 hours of evolution. Images are 2 degrees wide.
_
C_2023P1_20230908.jpg
C_2023P1_20230909.jpg

Nice to see this in real time, thanks for sharing.

[johnnydeep]

I've never seen a comet that changed its appearance so quickly. The solar wind and radiation is really tearing at it. These are from this morning and from yesterday morning, so just 24 hours of evolution. Images are 2 degrees wide.
_
C_2023P1_20230908.jpg
C_2023P1_20230909.jpg

Is it just my imagination, or is the first image much sharper and/or brighter?

[Chris Peterson]

I've never seen a comet that changed its appearance so quickly. The solar wind and radiation is really tearing at it. These are from this morning and from yesterday morning, so just 24 hours of evolution. Images are 2 degrees wide.
_
C_2023P1_20230908.jpg
C_2023P1_20230909.jpg

Is it just my imagination, or is the first image much sharper and/or brighter?

Not your imagination. I may play around with the processing some more, but over just one day more of the subs were taken against a brighter sky. I only have about a ten minute window between it rising and the sky being too bright to image at all. A window that is shrinking fast. So the S/N is poorer on the second. Maybe seeing issues, too. I'm shooting this about 5 degrees elevation.

[johnnydeep]

I've never seen a comet that changed its appearance so quickly. The solar wind and radiation is really tearing at it. These are from this morning and from yesterday morning, so just 24 hours of evolution. Images are 2 degrees wide.
_
C_2023P1_20230908.jpg
C_2023P1_20230909.jpg

Is it just my imagination, or is the first image much sharper and/or brighter?

Not your imagination. I may play around with the processing some more, but over just one day more of the subs were taken against a brighter sky. I only have about a ten minute window between it rising and the sky being too bright to image at all. A window that is shrinking fast. So the S/N is poorer on the second. Maybe seeing issues, too. I'm shooting this about 5 degrees elevation.

[orin stepanek]

I probably wake up early enough; but !'m not ambitious enough to
go looking!

McNaught is very Beautiful!

[alter-ego]

I've never seen a comet that changed its appearance so quickly. The solar wind and radiation is really tearing at it. These are from this morning and from yesterday morning, so just 24 hours of evolution. Images are 2 degrees wide.
_
C_2023P1_20230908.jpg
C_2023P1_20230909.jpg

Nice images.
I'm curious how you tracked the comet. Through scope auto guiding or image stacking control?

[Chris Peterson]

I've never seen a comet that changed its appearance so quickly. The solar wind and radiation is really tearing at it. These are from this morning and from yesterday morning, so just 24 hours of evolution. Images are 2 degrees wide.
_
C_2023P1_20230908.jpg
C_2023P1_20230909.jpg

Nice images.
I'm curious how you tracked the comet. Through scope auto guiding or image stacking control?

Those exposures were so short (on the order of 5 or 6 minutes total, stacked from 10 or 15 second subs), and the field wide enough, that I just let a small, roughly polar aligned mount track the sky. Then I aligned on the comet. You can see that the stars are trailed slightly. Longer exposures at a longer focal length (https://www.cloudbait.com/c2023p1.php) I actively tracked on the comet (but unguided), then created image pairs, one aligned on the comet and one on the stars, which I combined so that neither was trailed.

[alter-ego]

I've never seen a comet that changed its appearance so quickly. The solar wind and radiation is really tearing at it. These are from this morning and from yesterday morning, so just 24 hours of evolution. Images are 2 degrees wide.
_
C_2023P1_20230908.jpg
C_2023P1_20230909.jpg

Nice images.
I'm curious how you tracked the comet. Through scope auto guiding or image stacking control?

Those exposures were so short (on the order of 5 or 6 minutes total, stacked from 10 or 15 second subs), and the field wide enough, that I just let a small, roughly polar aligned mount track the sky. Then I aligned on the comet. You can see that the stars are trailed slightly. Longer exposures at a longer focal length (https://www.cloudbait.com/c2023p1.php) I actively tracked on the comet (but unguided), then created image pairs, one aligned on the comet and one on the stars, which I combined so that neither was trailed.

Makes sense for the wider FoV. For the longer exposure images I'm missing something. Regarding the image combination technique, how you end up with no trails in the final combination. It seems the comet is muddled slightly when aligned on the stars, and the stars are trailed if aligned on the comet .
Lastly, Are you using your guide scope the track the coma/nucleus?
BTW, your RC is a great upgrade from you're Meade

[Ann]

I've never seen a comet that changed its appearance so quickly. The solar wind and radiation is really tearing at it. These are from this morning and from yesterday morning, so just 24 hours of evolution. Images are 2 degrees wide.
_
C_2023P1_20230908.jpg
C_2023P1_20230909.jpg

The ion tail looks green in your images, Chris. That's not right, is it?

Or are we seeing the blue ion tail superimposed on a yellow dust tail, creating a green appearance?

Ann

[Chris Peterson]

Nice images.
I'm curious how you tracked the comet. Through scope auto guiding or image stacking control?

Those exposures were so short (on the order of 5 or 6 minutes total, stacked from 10 or 15 second subs), and the field wide enough, that I just let a small, roughly polar aligned mount track the sky. Then I aligned on the comet. You can see that the stars are trailed slightly. Longer exposures at a longer focal length (https://www.cloudbait.com/c2023p1.php) I actively tracked on the comet (but unguided), then created image pairs, one aligned on the comet and one on the stars, which I combined so that neither was trailed.

Makes sense for the wider FoV. For the longer exposure images I'm missing something. Regarding the image combination technique, how you end up with no trails in the final combination. It seems the comet is muddled slightly when aligned on the stars, and the stars are trailed if aligned on the comet .
Lastly, Are you using your guide scope the track the coma/nucleus?
BTW, your RC is a great upgrade from you're Meade :!: 👍

I use one of two techniques, depending on how much motion I have between subs. One approach simply involves stacking the images with some kind of median pixel rejection. If there is enough movement between frames, the stuff that's moving gets eliminated. I can extend this method by doing several stacks, taking say every three frames so there is more movement. If I do it with RGB filters, that happens automatically.

When there is less movement, I remove the stars from the subs (using one of several star removal tools) and then align on the comet and stack. That gives me a good comet image. Then I align on the stars, remove them (leaving the smeared comet behind) and add the stars into the comet image. Processing comets is quite a bit of work!

I have not had good luck trying to guide on comets. The problem is that they usually are sliding past stars, and those stars sometimes pass through the guide aperture, creating a guiding error. What I do is set the mount to guide on the comet. That is, it adjusts its tracking speed on both axes to match what is calculated from the comet orbital elements. That is open loop, but the tracking is very good so there is not much drift, and it is easily accommodated in post-processing by alignment methods.

[alter-ego]

Those exposures were so short (on the order of 5 or 6 minutes total, stacked from 10 or 15 second subs), and the field wide enough, that I just let a small, roughly polar aligned mount track the sky. Then I aligned on the comet. You can see that the stars are trailed slightly. Longer exposures at a longer focal length (https://www.cloudbait.com/c2023p1.php) I actively tracked on the comet (but unguided), then created image pairs, one aligned on the comet and one on the stars, which I combined so that neither was trailed.

Makes sense for the wider FoV. For the longer exposure images I'm missing something. Regarding the image combination technique, how you end up with no trails in the final combination. It seems the comet is muddled slightly when aligned on the stars, and the stars are trailed if aligned on the comet .
Lastly, Are you using your guide scope the track the coma/nucleus?
BTW, your RC is a great upgrade from you're Meade

I use one of two techniques, depending on how much motion I have between subs. One approach simply involves stacking the images with some kind of median pixel rejection. If there is enough movement between frames, the stuff that's moving gets eliminated. I can extend this method by doing several stacks, taking say every three frames so there is more movement. If I do it with RGB filters, that happens automatically.

When there is less movement, I remove the stars from the subs (using one of several star removal tools) and then align on the comet and stack. That gives me a good comet image. Then I align on the stars, remove them (leaving the smeared comet behind) and add the stars into the comet image. Processing comets is quite a bit of work!

I have not had good luck trying to guide on comets. The problem is that they usually are sliding past stars, and those stars sometimes pass through the guide aperture, creating a guiding error. What I do is set the mount to guide on the comet. That is, it adjusts its tracking speed on both axes to match what is calculated from the comet orbital elements. That is open loop, but the tracking is very good so there is not much drift, and it is easily accommodated in post-processing by alignment methods.

Thanks for the additional detail - very helpful. I figured you could easily "erase" open-space stars, but I didn't see how to deal with stars in the comet.
I did suspect you could track the comet good enough by inputting the orbital elements. I've not done it, but my old RCX400 Meade supposedly can track satellites, so I fully expected your setup most likely has that added capability.
I'm thinking you could have used PixInsight somewhere in the process. I really go for powerful image software for analysis purposes (I'm a fair-weather, crude astrophographer ) and considered buying it a year or two ago. Even though it's a one-time expense, I just couldn't justify the cost (yet).

[Chris Peterson]

Makes sense for the wider FoV. For the longer exposure images I'm missing something. Regarding the image combination technique, how you end up with no trails in the final combination. It seems the comet is muddled slightly when aligned on the stars, and the stars are trailed if aligned on the comet .
Lastly, Are you using your guide scope the track the coma/nucleus?
BTW, your RC is a great upgrade from you're Meade :!: 👍

I use one of two techniques, depending on how much motion I have between subs. One approach simply involves stacking the images with some kind of median pixel rejection. If there is enough movement between frames, the stuff that's moving gets eliminated. I can extend this method by doing several stacks, taking say every three frames so there is more movement. If I do it with RGB filters, that happens automatically.

When there is less movement, I remove the stars from the subs (using one of several star removal tools) and then align on the comet and stack. That gives me a good comet image. Then I align on the stars, remove them (leaving the smeared comet behind) and add the stars into the comet image. Processing comets is quite a bit of work!

I have not had good luck trying to guide on comets. The problem is that they usually are sliding past stars, and those stars sometimes pass through the guide aperture, creating a guiding error. What I do is set the mount to guide on the comet. That is, it adjusts its tracking speed on both axes to match what is calculated from the comet orbital elements. That is open loop, but the tracking is very good so there is not much drift, and it is easily accommodated in post-processing by alignment methods.

Thanks for the additional detail - very helpful. I figured you could easily "erase" open-space stars, but I didn't see how to deal with stars in the comet.
I did suspect you could track the comet good enough by inputting the orbital elements. I've not done it, but my old RCX400 Meade supposedly can track satellites, so I fully expected your setup most likely has that added capability.
I'm thinking you could have used PixInsight somewhere in the process. I really go for powerful image software for analysis purposes (I'm a fair-weather, crude astrophographer :ssmile: ) and considered buying it a year or two ago. Even though it's a one-time expense, I just couldn't justify the cost (yet).

Yes, I use PixInsight for almost all of the pre- and post-processing. I often take the nearly finished image into Photoshop for final cropping and annotation. There are a couple of star removal tools that run inside PI, and do a really excellent job. They will isolate stars from all sorts of background, including nebulas and comets.