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
From: az-observing-bounce@xxxxxxxxxxxxx <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
Has anyone seen anything similar before and know what the root cause is?
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