M8, M16, M20 and M83 - ST9 + RC

[bloodhound31]

Originally Posted by AlexN

.. Although I do think its more an affect of poor focus than processing downfall... Time will tell..

Alex.

I agree, it looks like focus. The first step in correcting a fault is correct fault diagnosis.

Baz.

[AlexN]

don't i know it baz. Don't i know it.

[RobF (Rob)]

Glad to see you both had fun!
Picked a great night for it too.

[troypiggo (Troy)]

Awesome shots. Friday and Saturday were quite good for us here.

[Peter Ward]

Alex,

Your subs are way too short for your sky background. That's what is causing the fixed pattern noise (herringbone like pattern) in the data. Try at least 10 minutes.

[Peter Ward]

Just to clarify my last post....

To be correct, fixed pattern noise is the wrong term. I simply used it as it best described what the noise "looks" like.

In Alex's case we are getting shot noise, (which reduces with exposure time) on top of less than perfect calibration data. When you stack images that are drifting in a uniform direction the end result is a herringbone pattern in the stacked data.

This pattern disappears with nil drift plus applying a random dither to the guide star tracking.

[kinetic (Steve)]

You are certainly getting there Alex,
can't wait for some LRGB!

Originally Posted by Peter Ward

When you stack images that are drifting in a uniform direction the end result is a herringbone pattern in the stacked data.

This pattern disappears with nil drift plus applying a random dither to the guide star tracking.

Peter,

I don't doubt your knowledge of the subject at all, but I have also noticed
this pattern on a few of my DS stacks with a drive artifact similar.
I can totally remove it with a better corrected dark frame (bad pxel
mapping in Nebulosity). Sorry for the OT post Alex!

Steve

[AlexN]

all is good guys.. I agree, I shouldnt be using auto-darks, its just that its so convenient..

Peter, You're right, longer subs would be the key... I'm just not too adept at processing out star blooms yet, so I try to avoid stars blooming by keeping the subs short.. Any ideas on processing the blooms out would be appreciated... I also don't know how to dither guiding yet... I've read about it, and would like to be doing it, just unsure how..

Cheers for the comments and constructive criticism everyone... I will endeavour to produce more, better (hopefully colour) images soon!