The Average Sigma Clip is the right algorithm. I am just surprised it did not
remove them. Is there a slider to adjust the high sigma clipping? Try lowering
that to 2 and see if that helps.
From: az-observing-bounce@xxxxxxxxxxxxx <az-observing-bounce@xxxxxxxxxxxxx> On
Behalf Of Michael McDonald
Sent: Saturday, October 13, 2018 11:16 AM
Subject: [AZ-Observing] Re: Hot Pixel tracks?
From everything I’ve read, I was under the impression that the hot pixels were
a “defect” in the imager. As such they should be the same pixel(s) in every
frame, including your dark master. Which allows the master dark to subtract out
the hot pixels. I’ve never run across anything suggesting that hot pixels can
move frame to frame.
I used the “Average Sigma Clip” rejection algorithm in PixInsight’s
ImageIntegration tool. Somewhere I read that that was good for < than 10
subframes, “Winsorized Sigma Clip” was the best for 10 to 20 subframes and
“Linear Fit Clip” was best for more than 20 subframes.
I’ll try some of the other rejection algorithms to see if they do any better.
On Oct 13, 2018, at 11:03 AM, Bernard Miller <bgmiller011@xxxxxxx> wrote:
Every camera has hot and/or cold pixels. This is usually removed during
processing by using a sigma rejection algorithm while stacking. This
algorithm looks at the mean of all the pixels and rejects any pixel that is a
certain sigma above the mean (usually 2-3 sigma). With only 7 frames, it is
sometimes better to use a Poisson sigma rejection algorithm for stacking. I
am surprised Pixinsight did not remove these pixels since I know it has these
or similar algorithms.
<az-observing-bounce@xxxxxxxxxxxxx> On Behalf Of Michael McDonald
Sent: Saturday, October 13, 2018 10:51 AM
Subject: [AZ-Observing] Hot Pixel tracks?
Here’s my one attempt at taking an image at last week’s AASP. It consists of
seven 3 minute subframes taken with my Canon SL1 with my Canon EF200f2.8L
lens on my Star Adventurer. The subframes were then stacked in PixInsight.
At first glance, it’s not too bad. (For me!) But if you look closer, there
are hot pixel tracks all over the image! All of the tracks are 7 pixels long,
which happens to corresponds to the number of subframes. So I went back and
looked at the original images and low and behold there is a hot pixel in each
original subframe. And it’s not the same pixel that’s hot, but moves slightly
frame to frame.
Has anyone seen anything similar before and know what the root cause is?
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