[Theme] Night sky shots

[Øivind Tøien]

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!

Thanks for the comment Akira. Yes I am also leaning towards the last version with blue background.

[Thomas Stellwag]

one more vote for the last one
your work to obtain these images is fascinating

[Øivind Tøien]

Thanks Thomas.

[Brute]

Great comet shots Oivind.

[Nasos Kosmas]

Excellent shots Oivid once more

A couple of clean sky evenings  to shot the comet for me, so I garbed the opportunity
Unfortunately I didn't move  out of town as I would like to do, so town light pollution  was present
I used the 85mm 1.8 to locate the comet and then the old 80-200 Af D to make the shots at 200mm, then I added an 1.4 TC to 280mm f 4 ( I am no longer owner of the excellent 300 pf ...)
I used the Interval timer shooting of Z8 to grab 100 shots at about 1 sec f4 ISO 6400, then stacked on Sequator
 
The final result is not bad but because of light pollution the  camera was not able to record the comets big tail and the smaller stars around.

Second Image is from previous day with 200 mm f 2.8,  1.6 sec ISO 1000  because of the longer  time there is a trail on the stars but is overall richer

Thank you

[Nasos Kosmas]

Another stack with different settings on Sequator, enhanced details

[Øivind Tøien]

Thanks Brute and Nasos. Very nice captures Nasos, the core is so round and well defined in the last one! As time goes by now the appearance of the tail is fading as the distance to the the sun is getting longer.

[Nasos Kosmas]

And finally I've got the opportunity  to capture the comet C/2023 A3A yesterday 27/10  in a less light pollution area
On the upper middle area of the frame you may see cluster IC 4665.
   
Nikon Z8 , 80-200 Af-D , 200mm f 3.2 , 1.6 sec  Iso 6400

50 Full Crop frames   Stacked  on Sequator.
Thank you

[Øivind Tøien]

Another nice comet capture, Nasos!

The winter storm blew out here (after causing everything to be encased in ice...), so I got an unexpected second opportunity on C/2023 A3 Tsuchinshan-Atlas Friday October 25. I did multiple sequences using Z8's 32 frame pixel shift mode to cause a minimal amount of dithering. For this first processing I used 20 frames over 10 min to minimize smearing of the core captured with the 300mm f/4 PF with f/4.5 front aperture, 30 sec ISO 500. The best view to SW was from my previous location on campus, unfortunately with lots of light pollution from street lights and the city, but at least no moonlight. The comet had faded considerably - I had to first home in using my 105mm lens before mounting the 300PF. For the first time I used Siril for the stacking and further processing, following a non-comet tutorial, with minimal adjustments in CNX2. The reverse tail is mostly gone (with some imagination there is an assymetric diffuse area in "front" of the core). The warm star Cebalrai is prominently catching the fading tail, with the cold Muliphen at the left edge.

[Akira]

And finally I've got the opportunity  to capture the comet C/2023 A3A yesterday 27/10  in a less light pollution area
On the upper middle area of the frame you may see cluster IC 4665.
   
Nikon Z8 , 80-200 Af-D , 200mm f 3.2 , 1.6 sec  Iso 6400

50 Full Crop frames   Stacked  on Sequator.
Thank you

This is an amazing result for a set of "usual" camera rig.  It looks much crisper than the previous images.  Amazing!

[ColinM]

Another beautiful capture Øivind

The warm star Cebalrai is prominently catching the fading tail,
with the cold Muliphen at the left edge.

There are 3 prominent stars in this image (the 3rd above and to the R of the comet body)
Each has clear black "bars" on either side.
Care to comnent on these?

[Akira]

Another beautiful capture Øivind

There are 3 prominent stars in this image (the 3rd above and to the R of the comet body)
Each has clear black "bars" on either side.
Care to comnent on these?

Colin, this African-talking-drum-like shape is not the shape of the star.  It is caused by the diffraction generated by the lens barrel.

[Øivind Tøien]

Thanks, Colin. Yes Akira is correct, it is diffraction caused by smaller obstacles or shapes in the lens barrel. The front aperture (a 77-67mm step down ring) is intended to help prevent this and create a round aperture. However it seems to be harder to avoid when using a full frame sensor with bright stars closer to the edges. There is of course a tradeoff in terms of the light lost to the front aperture, so if it does not help much it is perhaps best to abandon it instead of using an even narrower front aperture. On the first comet captures I did not use it. (On captures with scopes that use a spider there are typically four very prominent diffraction spikes.)

[Nasos Kosmas]

Thank you Oivid and Akira for your kind words 
 It was windy and some of the 50 captures was not in focus 100% so the stars became unnaturally bigger
The head of the comet also became  light full and not so smooth like Oivids  capture
Oivid did you found Siril more capable than Sequator?

[Øivind Tøien]

Thank you Oivid and Akira for your kind words 
 It was windy and some of the 50 captures was not in focus 100% so the stars became unnaturally bigger
The head of the comet also became  light full and not so smooth like Oivids  capture
Oivid did you found Siril more capable than Sequator?

Thanks Nasos, yes Siril is definitely much more capable. The way I have used Sequator has a tendency of blowing out highlights, perhaps increasing contrast too much. The background subtraction is also more advanced in Siril with much more control. It also has a what is called Photometric color calibration which is based on plate solving and database lookup on star colors. (It worked on the comet captures, but I am currently troubling with the plate solving on an old capture of North America Nebula.) If linear results from DSS stacks have been saved in fits files, they can also be further processed in Siril. The advantage is a workflow in linear space that is less prone to mess up colors as when stretching is done in non-linear space (e.g. in CNX2). It is going to take some time getting comfortable with Siril, but forward I think that will be well worth the effort. It is also nice that it is free and open source.