Chroma 3nm halo

[Starflyer]

I don't see halos, they're more like concentric rings to me. The bottom right star looks smeared by sensor tilt or spacing with some hint of triangular stars in that part of the image in general.

 

 

[Ken82]

The stars do look a little oddly shaped to me, maybe guiding and or collimation.

You can definitely see the concentric rings though. It would be very interesting to see the same camera/filters on another scope. 

Ken 

[souls33k3r]

1 hour ago, Whirlwind said:

I'm a bit confused but I don't see any ringing on these images?

I've marked the stars for you. You'll have to zoom in to see that. 

[Whirlwind]

Ah OK, I see them now, I used the bottom right one but couldn't see it (compression on my screen perhaps) but there are some better ones. I'll do some measuring tomorrow.

[Whirlwind]

On 23/11/2020 at 21:35, souls33k3r said:

I've marked the stars for you. You'll have to zoom in to see that. 

Are these the same two images or is the second one an uncompressed version of the first?  The plate solving of each one is completely different and there is obvious fixed pattern noise in the second compared to the first (which is much smoother and more random).  In the latter the ringing artefacts are much more apparent though.

[souls33k3r]

10 minutes ago, Whirlwind said:

Are these the same two images or is the second one an uncompressed version of the first?  The plate solving of each one is completely different and there is obvious fixed pattern noise in the second compared to the first (which is much smoother and more random).  In the latter the ringing artefacts are much more apparent though.

For the love of God I can't remember. I think they're the same but the only difference is that the first image was right out from PI and the second one (marked with red) was something I did on my phone. If that made difference to the file then I don't know

[Whirlwind]

20 minutes ago, souls33k3r said:

For the love of God I can't remember. I think they're the same but the only difference is that the first image was right out from PI and the second one (marked with red) was something I did on my phone. If that made difference to the file then I don't know

I've attached a comparison of the same stars between the image that shows that different in resolution.  The ringed one was giving a focal length of around 3500mm which seems high.  Also found out where the fixed noise was coming from. Apparently it was being added by the platesolve so that query is resolved.

[souls33k3r]

24 minutes ago, Whirlwind said:

I've attached a comparison of the same stars between the image that shows that different in resolution.  The ringed one was giving a focal length of around 3500mm which seems high.  Also found out where the fixed noise was coming from. Apparently it was being added by the platesolve so that query is resolved.

If you want and helps, I can send you a higher res image?

[Whirlwind]

Yeah, that would help as there is some compression issues happening somewhere?

[souls33k3r]

32 minutes ago, Whirlwind said:

Yeah, that would help as there is some compression issues happening somewhere?

Try this now mate. 

https://we.tl/t-cuhXf0sM8t

 

[Spongey]

Not sure if this was resolved for you but I've been reading this thread on CN and it might be of interest to you.

The whole thread is worth reading for background info but in particular posts #276 and #278 detail the problem you're having and the potential cause (in short, this is not caused by the filters and is instead due to centrally obstructed optics producing an extended airy disk which is being detected by the camera).

Edited December 23, 2020 by Spongey

[souls33k3r]

25 minutes ago, Spongey said:

Not sure if this was resolved for you but I've been reading this thread on CN and it might be of interest to you.

The whole thread is worth reading for background info but in particular posts #276 and #278 detail the problem you're having and the potential cause (in short, this is not caused by the filters and is instead due to centrally obstructed optics producing an extended airy disk which is being detected by the camera).

Thank you for the link mate. Unfortunately I haven't had the chance to test anything since I last posted because of the spell of bad weather we've been going through. I do however plan to test this with another scope on the next clear night which who knows when is coming. I'd be sure to update this thread with the findings. 

[Ken82]

Hi @souls33k3r

Last night I got a few OIII subs of the horse head/alnitak. For the first time since using chroma filters I can see a very very slight effect similar to the one you’ve posted. 
 

To be fair it doesn’t impact the image and it’s also an exceptionally bright star so I’m in no way complaining but thought I’d share. 
 

What’s very interesting is that I took 10 subs before meridian flip and had a look at the stack which had the effect. I then performed a flip and continued imaging. But after the meridian flip the effect had gone completely even in a similar stack of images. 
 

Could the conditions be the cause? Maybe position of the star when the light hits the filter ?? But to be fair the star was almost “on axis” on both occasions. Odd 

Maybe someone technical like @vlaiv would know better ??

ken 

 

[vlaiv]

I'm not seeing the effect? Can you point it out for me?

Only thing I see is better seeing in left stack (tighter stars).

[Ken82]

5 minutes ago, vlaiv said:

I'm not seeing the effect? Can you point it out for me?

Only thing I see is better seeing in left stack (tighter stars).

It’s not really what I would call a halo effect but it’s like a strange diffraction at either side of the bright star. @souls33k3r does appear to have it on dimmer stars but as yet I’ve only noticed a very slight effect like this on alnitak. 
 

Odd that it would disappear after meridian flip 🤔

 

[vlaiv]

I see two possible things happening here:

1. effect needs perfectly parallel surfaces or something and flip caused slight tilt - not enough to cause other optical problems but enough to offset the effect

2. first set of subs indeed has better seeing - star light is more concentrated and because of this effect has higher SNR and can be seen - while in second stack seeing took a turn to the worse and things are smeared out more and so is effect and it's overall SNR is not enough to show it clearly - it is still there but drowned in the noise?

Wild guesses really - but maybe I'll help ...

[inFINNity Deck]

I must have missed this thread back in November, but I think that the OP would appreciate my 5 cents input. Last year I had exactly the same issue, but then with the combination ZWO ASI1600MM Cool Pro, SkyWatcher Esprit 150ED and ZWO 36mm unmounted filters. I wrote a thread on a Dutch forum, but that should properly translate when opened in Chrome. Especially the second image can be of interest as it shows the differences between the old style and new style ZWO NB filters, the old ones showing halos very similar to those by the OP:

http://www.starry-night.nl/forums/topic/halos-en-zwo-filters/

So, in the end I got myself a new set of ZWO Ha and Siii filters and that solved the issue. Now, I know that the OP has a different make of filters, but using a similar methodic approach should make clear which part in the imaging train is responsible for these halos.

Nicolàs