[Theme] Night sky shots

[Nasos Kosmas]

Excellent shot Oivid! I think stacking with tracker makes all the difference

Thank you Akira 

[Øivind Tøien]

Thanks Bent, Akira and Nasos. So glad I got to catch it and also that I took the trouble of bringing the tracker. It is clearing after a cloudy morning so it might look good for the official star party tonight. The thin anti tail appears to be caused by larger particles left in the comets path while the major tail is light particles blowing away from the sun.

[armando_m]

Thanks Bent, Akira and Nasos. So glad I got to catch it and also that I took the trouble of bringing the tracker. It is clearing after a cloudy morning so it might look good for the official star party tonight. The thin anti tail appears to be caused by larger particles left in the comets path while the major tail is light particles blowing away from the sun.

Superb image, congrats!

[Øivind Tøien]

Thanks, Armando.

[Hugh_3170]

Congratulations Øivind - I am so pleased for you that you got a shot as clear as this one.

We have had a lot of rain in my area and have had a heavily overcast sky for several days, so alas no comet to be seen! 

To my joy, some clouds in the south-west mostly dissolved tonight so I got to have a go at Comet C/2023 A3 Tsuchinshan-Atlas. By eye it was only just possible to see the core with 8x20 binocular, while once it got dark enough the tail clearly showed in live view on the Z8. With time more people appeared so it became a little star party. I did both tracked and untracked exposures with 105mm f/2.5 AIS and the 300mm f/4 PF. Here is my early quick processing of a stack of tracked 8sec exposures over 5 min (to not elongate the core too much as it is tracked on the stars) with the 300PF. I am happy to also have caught the forward tail.

[aerobat]

To my joy, some clouds in the south-west mostly dissolved tonight so I got to have a go at Comet C/2023 A3 Tsuchinshan-Atlas. By eye it was only just possible to see the core with 8x20 binocular, while once it got dark enough the tail clearly showed in live view on the Z8. With time more people appeared so it became a little star party. I did both tracked and untracked exposures with 105mm f/2.5 AIS and the 300mm f/4 PF. Here is my early quick processing of a stack of tracked 8sec exposures over 5 min (to not elongate the core too much as it is tracked on the stars) with the 300PF. I am happy to also have caught the forward tail.

I'm deeply impressed Øivind - you put the 300mm PF to very good use

[Øivind Tøien]

Thanks Hugh and Daniel. We had a beautiful clear day yesterday - that is until 6:30 PM when non-transparent foggy clouds moved in and canceled the planned official comet party. So I am so glad I followed my hunch (based on Astrospheric, and not NWS) and got in my captures the evening before and that there at least were some others there that got to see it, including one other photographer. We are facing a serious winter storm though the coming week so this was likely our only chance at it.

This is still a work in progress, but I processed some more stacks in Sequator and used an alternative rendering that shows a bit more of the tail and background with the 300mm lens. The 105mm captures are closer to the live view image seen at the time at the back of the camera, the first of the two a short stack and the second a singel frame capture. There is a hint of the anti tail even in the stacked 105mm capture.

[Akira]

The first image seems to reveal that the anti-tail is longer than in the image on the previous page of the thread.

The comet captured during the "blue hour" looks fantastic.

[Øivind Tøien]

Thanks, Akira, the comet was moving quickly down towards the horizon and also in relation to the stars, so it is lower in the frame and less of the anti tail is showing in the second 300mm capture that was not reframed. The exposure was also shorter, 5 sec vs. 8 sec to see if I could get more details in the core. I might try the same processing on the first one too. I have more frames that was used for each stack, due to the need to limit motion of the comet relative to the stars. There are many different ways to process these captures - it was all blue hours in terms of the bright moonlight, so getting enough contrast was a bit challenging. The ones with the anti tail treated most of the background light as "light pollution" that was subtracted, thus the darker background. I might try DeepSkystacker or even Siril when I get more time.

[Akira]

Thank you for the technical details.  I wonder if the software can detect the specific spectra of not only the sodium and mercury lighting but also those of LEDs to eliminating the light pollution.  Or, would the function be just the adjustment of the contrast appropriate for the night sky images?

[Øivind Tøien]

Thank you for the technical details.  I wonder if the software can detect the specific spectra of not only the sodium and mercury lighting but also those of LEDs to eliminating the light pollution.  Or, would the function be just the adjustment of the contrast appropriate for the night sky images?

Sequator when ticking on "reduce light pollution" does its own thing, but usually the manual procedure is to move up the cutoff to the left edge of each color's rgb histogram peak, in other words performing a color specific subtraction.

Sodium lamps have traditionally been treated at the filtering stage, but broadband LEDs are really hard to compensate for. What seems to be popular is using narrowband filters on full spectrum cameras to sample specific wavelengths of light present in astronomical targets, which creates a very different color palette. (But some targets like galaxies and comets are already pretty wide band.) I personally prefer the more natural look of unmodified cameras or perhaps combined with some H-alpha added to it.

[Akira]

Sequator when ticking on "reduce light pollution" does its own thing, but usually the manual procedure is to move up the cutoff to the left edge of each color's rgb histogram peak, in other words performing a color specific subtraction.

Sodium lamps have traditionally been treated at the filtering stage, but broadband LEDs are really hard to compensate for. What seems to be popular is using narrowband filters on full spectrum cameras to sample specific wavelengths of light present in astronomical targets, which creates a very different color palette. (But some targets like galaxies and comets are already pretty wide band.) I personally prefer the more natural look of unmodified cameras or perhaps combined with some H-alpha added to it.

Again, thank you for the detail.  Once captured in R, G and B channels, it might be difficult or impossible to eliminate the bright spectra.

The filter to pass like specific spectra like OIII are of the interference type and are only suitable for the narrower angle lenses.

I appreciate your effort to shot such amazing images mostly utilizing normal gear for the photography maybe except for the tracker.

[Frank Fremerey]

night sky in LA yesterday

[Øivind Tøien]

Yet another version of the comet for those who like the more natural moonlit background. This is based one the same captures as the first one posted, but stacked in DSS before working on it in CNX2. (Open in new tab to display larger version.)

[Akira]

Yet another version of the comet for those who like the more natural moonlit background. This is based one the same captures as the first one posted, but stacked in DSS before working on it in CNX2. (Open in new tab to display larger version.)

The latest image looks the most favorable to me.  It is slightly noisier, but the deep blue of the sky and the slightly clearer anti tail makes well up for the increased noise.  Again, thank you for sharing!