Author Topic: Streaks after integration  (Read 2419 times)

Offline neilbuc

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Streaks after integration
« on: 2015 November 08 02:31:47 »
Hello. I am pretty new using PI, but reaching out for a little help to see if this can be resolved in processing. I have 25x300s subs with Darks, Flats and Bias(superbias too) on IC1805 from Friday. For the first time I dithered with BYEOS and PHD2 (default settings). I am using a Canon 600d (modded) with a Lacerta OAG. Guiding looked excellent and smooth. Using the eSprit80 does not overly work my AZ EQ6-GT in any way.

So I followed the excellent tutorials on light vortex astronomy (brilliant btw) but when I integrate the images with winsorized sigma clipping I get these weird streaks.

I have tried all sorts of different stacking methods.The stars look nice and round so its not a flexture issue (OAG anyway).

Is it case that I need to dither more? Up the settings in BYEOS and PHD? If so to what value for a DSLR?

I spend a good 8 hours yesterday trawling the net for help, and most things said dither more. However is all this data useless? Can it be processed out?

Any pointers for a newbie would be great.

Clear Skies

Neil


Offline IanL

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Re: Streaks after integration
« Reply #1 on: 2015 November 08 06:24:30 »
Check the images before registration (StarAlignment).  If the stars are drifting across the frame in the direction of the streaks then that's your problem.  You need to polar align better to reduce the drift and / or dither more so that it stacks out.  With reasonable polar alignment a dither of 15 pixels or so usually works OK.  Many capture programs only go up to 5 pixels, but you can set a multiplier in PHD to 3 to scale up the dithering.

Offline neilbuc

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Re: Streaks after integration
« Reply #2 on: 2015 November 08 06:53:16 »
Thanks for the response Ian.

My polar alignment is pretty good. I use EQ mod first for general PA then a few iterations with Alignmaster. As this was the first time I have tried to dither, I will give the settings a tweak. The whole reason I dithered was to help remove some of the thermal noise as I use a DSLR just now. I was hoping that some dithering and sigma clipping integration would remove alot of the noise. This is the first time I have ever seen theses streaks. I though it was something I was doing wrong in PI, but perhaps not.

Cheers

Neil

Offline neilbuc

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Re: Streaks after integration
« Reply #3 on: 2015 November 08 10:21:51 »
Some more reading and cosmetic correction set more aggressively has yielded this.

Much better I think.


Offline gvanhau

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Re: Streaks after integration
« Reply #4 on: 2015 November 09 06:15:15 »
Hello

The Streaks seem to be caused by a small (but consistent) drift between shots, but it can also be bandign noise inherent to some DSLR's.

You could try the canon bandign noise removal scritp (look in the scripts menu).

The best way to avoid this is doing enouhg dithering between shots.

regards
Geert
Geert Vanhauwaert

Offline astroman2

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Re: Streaks after integration
« Reply #5 on: 2015 November 10 03:18:52 »
Hi,

I have seen this with my DSLR when the it was hotter than usual. So now I cool the camera and issue fixed.

One possible processing solution is here http://pixinsight.com.ar/en/info/processing-examples/19/crux-southern-cross.html.

Regards

Scott