Striations in Photos - Forums

Topic starter

Dec 20, 2020

Hey folks,

Wondering is anyone can give some advice on what might be causing diagonal "striations" (not sure how else to describe them) in my astrophotos. Issue is improved after noise reduction but still noticeable at high zoom. I'm not sure if this is coming from the capture process.

Working from my chromebook at the moment and screencapture isn't playing nicely but will update later from my desktop. You can see it in the full resolution version of my IC405 work in progress. That shot is a heavily processed integration of 25 Ha and 25 Oiii frames. I'll take a pass back thru some of the intermediate images later tonight to be sure, but I think it was there from the start. Images were dithered during capture and are all from the same night... I suppose it could be high clouds but i don't think so.

Appreciate any thoughts.

Corey

Engaging

Aaron Hakala

Dec 20, 2020

Hi Corey, I am pretty sure it is walking noise. I have had this myself a few times. I dither every third frame. I also went from small dither to “medium” dither. This made a big difference. What are you program are you using to initiate the dither? Is it PHD? Or a capture program?

Nev. Blyth

Dec 20, 2020

Hi Corey

Yes, as Aaron noted - this is very likely walking noise or 'correlated noise'.

Dithering is the go - I've been able to eliminate walking noise by dithering each sub. I'm experimenting with varying the dither amount with positive results too.

Great pic btw.

N

Concise

Corey Smart

Topic starter

Dec 20, 2020

Thanks, folks.

I am dithering, but perhaps it's not quite enough to offset the issue. Using SG Pro for capture, with guiding by PHD2. Looks like dithering was set to "Small Dither" on every image. I've typically used a larger dithering setting but was rebuilding the profiles for a new PC setup so maybe that's all I need to change. Clouds in the forecast for the next week at least, so not sure when I'll get to retry but will change that and see where it goes.

Interestingly I don't see the issue on other images from the same night / sequence, but I think those all involved a meridian flip as well. Might be that was enough to offset the problem for those targets.
Cheers and thanks to both for the feedback!

Corey

Respectful Supportive

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